ORCID Profile
0000-0003-2580-2336
Current Organisation
Curtin University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Evolutionary Biology | Biological Adaptation | Environmental Science and Management | Evolutionary Impacts of Climate Change | Conservation And Biodiversity | Ecology And Evolution Not Elsewhere Classified | Stochastic Analysis And Modelling | Evolutionary biology | Wildlife and Habitat Management | Evolutionary biology not elsewhere classified | Population Ecology | Host-Parasite Interactions | Life Histories | Conservation and Biodiversity | Terrestrial Ecology | Population ecology | Evolutionary ecology | Ecological Physiology | Biogeography and Phylogeography
ANZSRC Socio-Economic Objective (SEO)
Control of pests and exotic species | Flora, Fauna and Biodiversity at Regional or Larger Scales | Control of Pests, Diseases and Exotic Species at Regional or Larger Scales | Global climate change adaptation measures | Ecosystem Adaptation to Climate Change | Control of Pests, Diseases and Exotic Species in Marine Environments | Control of Pests, Diseases and Exotic Species in Fresh, Ground and Surface Water Environments | Climate Change Adaptation Measures | Control of Animal Pests, Diseases and Exotic Species in Farmland, Arable Cropland and Permanent Cropland Environments | Ecosystem Assessment and Management at Regional or Larger Scales | Control of pests and exotic species | Control of pests and exotic species | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Identification and dynamics of a cryptic suture zone in tropical rainforest
Publisher: The Royal Society
Date: 20-01-2009
Abstract: Suture zones, shared regions of secondary contact between long-isolated lineages, are natural laboratories for studying ergence and speciation. For tropical rainforest, the existence of suture zones and their significance for speciation has been controversial. Using comparative phylogeographic evidence, we locate a morphologically cryptic suture zone in the Australian Wet Tropics rainforest. Fourteen out of 18 contacts involve morphologically cryptic phylogeographic lineages, with mtDNA sequence ergences ranging from 2 to 15 per cent. Contact zones are significantly clustered in a suture zone located between two major Quaternary refugia. Within this area, there is a trend for secondary contacts to occur in regions with low environmental suitability relative to both adjacent refugia and, by inference, the parental lineages. The extent and form of reproductive isolation among interacting lineages varies across species, ranging from random admixture to speciation, in one case via reinforcement. Comparative phylogeographic studies, combined with environmental analysis at a fine-scale and across varying climates, can generate new insights into suture zone formation and to ersification processes in species-rich tropical rainforests. As arenas for evolutionary experimentation, suture zones merit special attention for conservation.
Infection in patchy populations: Contrasting pathogen invasion success and dispersal at varying times since host colonization
Publisher: Oxford University Press (OUP)
Date: 10-2019
DOI: 10.1002/EVL3.141
Abstract: Repeated extinction and recolonization events generate a landscape of host populations that vary in their time since colonization. Within this dynamic landscape, pathogens that excel at invading recently colonized host populations are not necessarily those that perform best in host populations at or near their carrying capacity, potentially giving rise to ergent selection for pathogen traits that mediate the invasion process. Rarely, however, has this contention been empirically tested. Using Daphnia magna, we explored how differences in the colonization history of a host population influence the invasion success of different genotypes of the pathogen Pasteuria ramosa. By partitioning the pathogen invasion process into a series of in idual steps, we show that each pathogen optimizes invasion differently when encountering host populations that vary in their time since colonization. All pathogen genotypes were more likely to establish successfully in recently colonized host populations, but the production of transmission spores was typically maximized in either the subsequent growth or stationary phase of host colonization. Integrating across the first three pathogen invasion steps (initial establishment, proliferation, and secondary infection) revealed that overall pathogen invasion success (and its variance) was, nonetheless, highest in recently colonized host populations. However, only pathogens that were slow to kill their host were able to maximize host-facilitated dispersal. This suggests that only a subset of pathogen genotypes—the less virulent and more dispersive—are more likely to encounter newly colonized host populations at the front of a range expansion or in metapopulations with high extinction rates. Our results suggest a fundamental trade-off for a pathogen between dispersal and virulence, and evidence for higher invasion success in younger host populations, a finding with clear implications for pathogen evolution in spatiotemporally dynamic settings.
There Is No Evidence for a Temporal Link between Pathogen Arrival and Frog Extinctions in North-Eastern Australia
Publisher: Public Library of Science (PLoS)
Date: 27-12-2012
Group resource-holding potential: worker size, colony size and the outcome of contests in ants
Publisher: Elsevier BV
Date: 04-2023
The toad ahead: challenges of modelling the range and spread of an invasive species
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/WR07101
Abstract: An ability to predict the rate at which an organism spreads its range is of growing importance because the process of spread (during invasion by an exotic species) is almost identical to that occurring at the expanding range margins of a native species undergoing range shifts in response to climate change. Thus, the methods used for modelling range spread can also be employed to assess the distributional implications of climate change. Here we review the history of research on the spread of cane toads in Australia and use this case study to broadly examine the benefits and pitfalls of various modelling approaches. We show that the problems of estimating the current range, predicting the future range, and predicting the spread rate are interconnected and inform each other. Generally, we argue that correlative approaches to range-prediction are unsuitable when applied to invasive species and suggest that mechanistic methods are beginning to look promising (despite being more difficult to execute), although robust comparisons of correlative versus mechanistic predictions are lacking. Looking to the future, we argue that mechanistic models of range advance (drawing from both population ecology and environmental variation) are the approaches most likely to yield robust predictions. The complexity of these approaches coupled with the steady rise in computing power means that they have only recently become computationally tractable. Thus, we suggest that the field is only recently in a position to incorporate the complexity necessary to robustly model the rate at which species shift their range.
Can pathogens optimize both transmission and dispersal by exploiting sexual dimorphism in their hosts?
Publisher: The Royal Society
Date: 06-2019
Abstract: Pathogens often rely on their host for dispersal. Yet, maximizing fitness via replication can cause damage to the host and an associated reduction in host movement, incurring a trade-off between transmission and dispersal. Here, we test the idea that pathogens might mitigate this trade-off between reproductive fitness and dispersal by taking advantage of sexual dimorphism in their host, tailoring responses separately to males and females. Using experimental populations of Daphnia magna and its bacterial pathogen Pasteuria ramosa as a test-case, we find evidence that this pathogen can use male hosts as a dispersal vector, and the larger females as high-quality resource patches for optimized production of transmission spores. As sexual dimorphism in dispersal and body size is widespread across the animal kingdom, this differential exploitation of the sexes by a pathogen might be an unappreciated phenomenon, possibly evolved in various systems.
Spatial sorting as the spatial analogue of natural selection
Publisher: Cold Spring Harbor Laboratory
Date: 27-10-2017
DOI: 10.1101/210088
Abstract: In most systems, dispersal occurs despite clear fitness costs to dispersing in iduals. Theory posits that spatial heterogeneity in habitat quality pushes dispersal rates to evolve towards zero, while temporal heterogeneity in habitat quality favours non-zero dispersal rates. One aspect of dispersal evolution that has received a great deal of recent attention is a process known as spatial sorting, which has been referred to as a “shy younger sibling” of natural selection. More precisely, spatial sorting is the process whereby variation in dispersal ability is sorted along density clines and will, in nature, often be a transient phenomenon. Despite this transience, spatial sorting is likely a general mechanism behind non-zero dispersal in spatiotemporally varying environments. While generally transient, spatial sorting is persistent on invasion fronts, where its effect cannot be ignored, causing rapid evolution of traits related to dispersal. Spatial sorting is described in several elegant models, yet these models require a high level of mathematical sophistication and are not accessible to most evolutionary biologists or their students. Here, we frame spatial sorting in terms of the classic haploid and diploid models of natural selection. We show that, on an invasion front, spatial sorting can be conceptualized precisely as selection operating through space rather than (as with natural selection) time, and that genotypes can be viewed as having both spatial and temporal aspects of fitness. The resultant model is strikingly similar to classic models of natural selection. This similarity renders the model easy to understand (and to teach), but also suggests that many established theoretical results around natural selection could apply equally to spatial sorting.
The morphology, and hence impact, of an invasive species (the cane toad, Bufo marinus: Changes with time since colonisation
Publisher: Wiley
Date: 11-2005
Effects of developmental environment on animal personality in a tropical skink
Publisher: Springer Science and Business Media LLC
Date: 22-09-2022
DOI: 10.1007/S00265-022-03240-3
Abstract: Developmental environments play a significant role in shaping animal phenotype, including behavior. Within a species, in iduals often differ in behavior in a consistent and repeatable way (i.e., demonstrate animal personality). This consistency in behavior can be affected by differences in conditions experienced early in life. It is, however, unclear whether effects of developmental environments on animal personality are driven by changes in within- or between-in idual variation. To investigate this, we measured activity, exploration, sociability, and boldness in adult male southern rainforest sunskinks, L ropholis similis , incubated at either 23 °C or 26 °C, and compared behavioral phenotypes between these incubation treatments. We also compared the behavior of these incubation groups to a cohort of wild-caught skinks to determine whether rearing in captivity also affected the personality of the lizards. Skinks that had been incubated at a higher temperature were more explorative and demonstrated personality in a larger suite of traits compared to lizards incubated at a lower temperature or caught in the wild. These differences among developmental environment were primarily driven by within-in idual variation, which tended to be higher among the high incubation treatment. We also found no evidence for a behavioral syndrome in either captive- or wild-reared skinks. Our results suggest the potential for greater behavioral plasticity in skinks incubated at a higher temperature, which may enable them to cope with environmental change, such as climate warming, in the short term. Overall, we show that effects of developmental environment are complex and play a pivotal role in shaping animal personality. Experiences during development are expected to influence how animals develop, including their behavior. We tested early environment effects on behavior in adult southern rainforest sunskinks by comparing lizards incubated at different temperatures as well as comparing those reared in the wild with those reared in captive environments. We found that lizards incubated at the higher temperature were more exploratory. Furthermore, both incubation temperature and captivity/wild-rearing had pronounced effects on the consistency of behavior—in different directions for different traits—demonstrating developmental environments have strong effects on animal personality. Such changes in behavioral traits likely have flow-on effects for the animal’s fitness and biotic interactions.
After the crash: How do predators adjust following the invasion of a novel toxic prey type?
Publisher: Wiley
Date: 15-05-2014
DOI: 10.1111/AEC.12058
Perverse outcomes from fencing fauna: Loss of antipredator traits in a havened mammal population
Publisher: Elsevier BV
Date: 05-2023
Locomotor performance in an invasive species: Cane toads from the invasion front have greater endurance, but not speed, compared to conspecifics from a long-colonised area
Publisher: Springer Science and Business Media LLC
Date: 16-10-2010
DOI: 10.1007/S00442-009-1471-1
Abstract: Cane toads (Bufo marinus) are now moving about 5 times faster through tropical Australia than they did a half-century ago, during the early phases of toad invasion. Radio-tracking has revealed higher daily rates of displacement by toads at the invasion front compared to those from long-colonised areas: toads from frontal populations follow straighter paths, move more often, and move further per displacement than do toads from older (long-established) populations. Are these higher movement rates of invasion-front toads associated with modified locomotor performance (e.g. speed, endurance)? In an outdoor raceway, toads collected from the invasion front had similar speeds, but threefold greater endurance, compared to conspecifics collected from a long-established population. Thus, increased daily displacement in invasion-front toads does not appear to be driven by changes in locomotor speed. Instead, increased dispersal is associated with higher endurance, suggesting that invasion-front toads tend to spend more time moving than do their less dispersive conspecifics. Whether this increased endurance is a cause or consequence of behavioural shifts associated with rapid dispersal is unclear. Nonetheless, shifts in endurance between frontal and core populations of this invasive species point to the complex panoply of traits affected by selection for increased dispersal ability on expanding population fronts.
Turgid female toads give males the slip: a new mechanism of female mate choice in the Anura
Publisher: The Royal Society
Date: 06-01-2010
Abstract: In many anuran species, males vocalize to attract females but will grasp any female that comes within reach and retain their hold unless displaced by a rival male. Thus, female anurans may face strong selection to repel unwanted suitors, but no mechanism is known for doing so. We suggest that a defensive trait (the ability to inflate the body to ward off attack) has been co-opted for this role: by inflating their bodies, females are more difficult for males to grasp and hence, it is easier for another male to displace an already lexed rival. Inflating a model female cane toad ( Bufo marinus ) strongly reduced a male's ability to maintain lexus and females who were experimentally prevented from inflating their bodies experienced no successful takeovers from rival males, in contrast to control females. Thus, the ability of a female cane toad to inflate her body may allow her to manipulate the outcome of male–male competition. This overlooked mechanism of anuran mate choice may reflect a common evolutionary pattern, whereby females co-opt defensive traits for use in sexual selection.
Do dingoes suppress the activity of feral cats in northern Australia?
Publisher: Wiley
Date: 27-04-2011
An invasive species induces rapid adaptive change in a native predator: cane toads and black snakes in Australia.
Publisher: The Royal Society
Date: 21-03-2006
Abstract: Rapid environmental change due to human activities has increased rates of extinction, but some species may be able to adapt rapidly enough to deal with such changes. Our studies of feeding behaviour and physiological resistance to toxins reveal surprisingly rapid adaptive responses in Australian black snakes ( Pseudechis porphyriacus ) following the invasion of a lethally toxic prey item, the cane toad ( Bufo marinus ). Snakes from toad-exposed localities showed increased resistance to toad toxin and a decreased preference for toads as prey. Separate laboratory experiments suggest that these changes are not attributable to learning (we were unable to teach naive snakes to avoid toxic prey) or to acquired resistance (repeated sub-lethal doses did not enhance resistance). These results strongly suggest that black snake behaviour and physiology have evolved in response to the presence of toads, and have done so rapidly. Toads were brought to Australia in 1935, so these evolved responses have occurred in fewer than 23 snake generations.
Adaptation or preadaptation: Why are keelback snakes (Tropidonophis mairii) less vulnerable to invasive cane toads (Bufo marinus) than are other Australian snakes?
Publisher: Springer Science and Business Media LLC
Date: 19-03-2011
Energetic scaling across different host densities and its consequences for pathogen proliferation
Publisher: Wiley
Date: 08-12-2021
Abstract: The spread of infectious disease is determined by the ability of a pathogen to proliferate within and spread between susceptible hosts. Processes that limit the performance of a pathogen thus occur at two scales: varying with both the availability of energy within a host, and the number of susceptible hosts in a patch. When the rate at which a host intakes and expends energy is density‐dependent, these two processes are intimately linked. By modifying how hosts compete for and expend resources, a shift in population density may contribute to differences in the flow of energy in a host–pathogen system, both in terms of the energy available for a host to grow, reproduce and fight infection, as well as the energy available for a pathogen to exploit. Energy flux, therefore, connects the two contrasting scales of within‐ and between‐host dynamics by directly linking the proliferation of a pathogen to the number of hosts circulating within a patch. We use the host Daphnia magna to explore the relationship between energy intake and expenditure at various population densities, as estimated by feeding and metabolic rates respectively. By infecting hosts with the bacterial pathogen Pasteuria ramosa , we then explore how infection changes the relative balance of energy intake and expenditure, and how this energy scope translates into production of transmission spores. Our work demonstrates that energy intake declines at a faster rate with density than does metabolic rate, leaving more excess energy (i.e. discretionary energy) available for both hosts and their dependent pathogens at low population densities. This energetic advantage translates positively into host and pathogen growth, with the production of mature transmission spores benefiting most from correlated changes in host body size, as well as a direct connection between energy scope and spore loads. Our findings reinforce how patch quality for a pathogen operates at two contrasting scales, with the within‐host proliferation of a pathogen being optimised in energy rich, low density host populations and opportunities for between‐host transmission likely maximised in dense populations. A free Plain Language Summary can be found within the Supporting Information of this article.
Comparisons through time and space suggest rapid evolution of dispersal behaviour in an invasive species
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/WR08021
Abstract: During a biological invasion, we expect that the expanding front will increasingly become dominated by in iduals with better dispersal abilities. Over many generations, selection at the invasion front thus will favour traits that increase dispersal rates. As a result of this process, cane toads (Bufo marinus) are now spreading through tropical Australia about 5-fold faster than in the early years of toad invasion but how have toads changed to make this happen? Here we present data from radio-tracking of free-ranging cane toads from three populations (spanning a 15-year period of the toads’ Australian invasion, and across 1800 km). Our data reveal dramatic shifts in behavioural traits (proportion of nights when toads move from their existing retreat-site to a new one, and distance between those successive retreat-sites) associated with the rapid acceleration of toad invasion. Over a maximum period of 70 years (~50 generations), cane toads at the invasion front in Australia apparently have evolved such that populations include a higher proportion of in iduals that make long, straight moves.
Trade‐offs and the evolution of life‐histories during range expansion
Publisher: Wiley
Date: 16-08-2010
DOI: 10.1111/J.1461-0248.2010.01505.X
Abstract: During range-advance, in iduals on the expanding edge of the population face a unique selective environment. In this study, we use a three-trait trade-off model to explore the evolution of dispersal, reproduction and competitive ability during range expansion. We show that range expansion greatly affects the evolution of life-history traits due to differing selection pressures at the front of the range compared with those found in stationary and core populations. During range expansion, dispersal and reproduction are selected for on the expanding population front, whereas traits associated with fitness at equilibrium density (competitive ability) show dramatic declines. Additionally, we demonstrate that the presence of a competing species can considerably reduce the extent to which dispersal is selected upwards at an expanding front. These findings have important implications for understanding both the rate of spread of invasive species and the range-shifting dynamics of native species in response to climate change.
Novel Predators can Elicit Rapid Shifts in Prey Demographics and Behavior
Publisher: Wiley
Date: 10-2021
DOI: 10.1002/BES2.1921
The evolution of growth rates on an expanding range edge
Publisher: The Royal Society
Date: 15-07-2009
Abstract: In iduals in the vanguard of a species invasion face altered selective conditions when compared with conspecifics behind the invasion front. Assortment by dispersal ability on the expanding front, for ex le, drives the evolution of increased dispersal, which, in turn, leads to accelerated rates of invasion. Here I propose an additional evolutionary mechanism to explain accelerating invasions: shifts in population growth rate ( r ). Because in iduals in the vanguard face lower population density than those in established populations, they should (relative to in iduals in established populations) experience greater r -selection. To test this possibility, I used the ongoing invasion of cane toads ( Bufo marinus ) across northern Australia. Life-history theory shows that the most efficient way to increase the rate of population growth is to reproduce earlier. Thus, I predict that toads on the invasion front will exhibit faster in idual growth rates (and thus will reach breeding size earlier) than those from older populations. Using a common garden design, I show that this is indeed the case: both tadpoles and juvenile toads from frontal populations grow around 30 per cent faster than those from older, long established populations. These results support theoretical predictions that r increases during range advance and highlight the importance of understanding the evolution of life history during range advance.
Cost and feasibility of a barrier to halt the spread of invasive cane toads in arid Australia: incorporating expert knowledge into model-based decision-making
Publisher: Wiley
Date: 10-08-2017
The role of behavioural variation in the invasion of new areas
Publisher: Oxford University Press
Date: 14-06-2015
Ethical Publishing: How Do We Get There?
Publisher: University of Michigan Library
Date: 21-10-2022
DOI: 10.3998/PTPBIO.3363
Abstract: The academic journal publishing model is deeply unethical: today, a few major, for-profit conglomerates control more than 50% of all articles in the natural sciences and social sciences, driving subscription and open-access publishing fees above levels that can be sustainably maintained by publicly funded universities, libraries, and research institutions worldwide. About a third of the costs paid for publishing papers is profit for these dominant publishers' shareholders, and about half of them covers costs to keep the system running, including lobbying, marketing fees, and paywalls. The paywalls in turn restrict access of scientific outputs, preventing them from being freely shared with the public and other researchers. Thus, money that the public is told goes into science is actually being funneled away from it, or used to limit access to it. Alternatives to this model exist and have increased in popularity in recent years, including diamond open-access journals and community-driven recommendation models. These are free of charge for authors and minimize costs for institutions and agencies, while making peer-reviewed scientific results publicly accessible. However, for-profit publishing agents have made change difficult, by co-opting open-access schemes and creating journal-driven incentives that prevent an effective collective transition away from profiteering. Here, we give a brief overview of the current state of the academic publishing system, including its most important systemic problems. We then describe alternative systems. We explain the reasons why the move toward them can be perceived as costly to in idual researchers, and we demystify common roadblocks to change. Finally, in view of the above, we provide a set of guidelines and recommendations that academics at all levels can implement, in order to enable a more rapid and effective transition toward ethical publishing.
Accounting for detectability and abundance in survey design for a declining species
Publisher: Wiley
Date: 21-07-2019
DOI: 10.1111/DDI.12966
Virgins in the vanguard: Low reproductive frequency in invasion-front cane toads
Publisher: Oxford University Press (OUP)
Date: 14-07-2015
DOI: 10.1111/BIJ.12618
Mechanisms and consequences of sexual conflict in garter snakes (Thamnophis sirtalis, Colubridae)
Publisher: Oxford University Press (OUP)
Date: 07-2004
Reid's paradox revisited: The evolution of dispersal kernels during range expansion
Publisher: University of Chicago Press
Date: 07-2008
DOI: 10.1086/588255
Abstract: Current approaches to modeling range advance assume that the distribution describing dispersal distances in the population (the "dispersal kernel") is a static entity. We argue here that dispersal kernels are in fact highly dynamic during periods of range advance because density effects and spatial assortment by dispersal ability ("spatial selection") drive the evolution of increased dispersal on the expanding front. Using a spatially explicit in idual-based model, we demonstrate this effect under a wide variety of population growth rates and dispersal costs. We then test the possibility of an evolved shift in dispersal kernels by measuring dispersal rates in in idual cane toads (Bufo marinus) from invasive populations in Australia (historically, toads advanced their range at 10 km/year, but now they achieve >55 km/year in the northern part of their range). Under a common-garden design, we found a steady increase in dispersal tendency with distance from the invasion origin. Dispersal kernels on the invading front were less kurtotic and less skewed than those from origin populations. Thus, toads have increased their rate of range expansion partly through increased dispersal on the expanding front. For accurate long-range forecasts of range advance, we need to take into account the potential for dispersal kernels to be evolutionarily dynamic.
The straight and narrow path: the evolution of straight-line dispersal at a cane toad invasion front
Publisher: The Royal Society
Date: 22-11-2014
Abstract: At the edge of a biological invasion, evolutionary processes (spatial sorting, natural selection) often drive increases in dispersal. Although numerous traits influence an in idual's displacement (e.g. speed, stamina), one of the most important is path straightness. A straight (i.e. highly correlated) path strongly enhances overall dispersal rate relative to time and energetic cost. Thus, we predict that, if path straightness has a genetic basis, organisms in the invasion vanguard will exhibit straighter paths than those following behind. Our studies on invasive cane toads ( Rhinella marina ) in tropical Australia clearly support this prediction. Radio-tracking of field-collected toads at a single site showed that path straightness steadily decreased over the first 10 years post-invasion. Consistent with an evolved (genetic) basis to that behavioural shift, path straightness of toads reared under common garden conditions varied according to the location of their parents' origin. Offspring produced by toads from the invasion vanguard followed straighter paths than did those produced by parents from long-established populations. At the in idual level, offspring exhibited similar path straightness to their parents. The dramatic acceleration of the cane toad invasion through tropical Australia has been driven, in part, by the evolution of a behavioural tendency towards dispersing in a straight line.
Anywhere but here: local conditions motivate dispersal in Daphnia
Publisher: PeerJ
Date: 12-03-2019
DOI: 10.7717/PEERJ.6599
Abstract: Dispersal is fundamental to population dynamics. However, it is increasingly apparent that, despite most models treating dispersal as a constant, many organisms make dispersal decisions based upon information gathered from the environment. Ideally, organisms would make fully informed decisions, with knowledge of both intra-patch conditions (conditions in their current location) and extra-patch conditions (conditions in alternative locations). Acquiring information is energetically costly, however, and extra-patch information will typically be costlier to obtain than intra-patch information. As a consequence, theory suggests that organisms will often make partially informed dispersal decisions, utilising intra-patch information only. We test this proposition in an experimental two-patch system using populations of the aquatic crustacean, Daphnia carinata . We manipulated conditions (food availability) in the population’s home patch, and in its alternative patch. We found that D. carinata made use of intra-patch information (resource availability in the home patch induced a 10-fold increase in dispersal probability) but either ignored or were incapable of using of extra-patch information (resource availability in the alternative patch did not affect dispersal probability). We also observed a small apparent increase in dispersal in replicates with higher population densities, but this effect was smaller than the effect of resource constraint, and not found to be significant. Our work highlights the considerable influence that information can have on dispersal probability, but also that dispersal decisions will often be made in only a partially informed manner. The magnitude of the response we observed also adds to the growing chorus that condition-dependence may be a significant driver of variation in dispersal.
Fire History from Life-History: Determining the Fire Regime that a Plant Community Is Adapted Using Life-Histories
Publisher: Public Library of Science (PLoS)
Date: 21-02-2012
Increasing arboreality with altitude: a novel biogeographic dimension
Publisher: The Royal Society
Date: 07-11-2013
Abstract: Bio ersity is spatially organized by climatic gradients across elevation and latitude. But do other gradients exist that might drive biogeographic patterns? Here, we show that rainforest's vertical strata provide climatic gradients much steeper than those offered by elevation and latitude, and bio ersity of arboreal species is organized along this gradient. In Philippine and Singaporean rainforests, we demonstrate that rainforest frogs tend to shift up in the rainforest strata as altitude increases. Moreover, a Philippine-wide dataset of frog distributions shows that frog assemblages become increasingly arboreal at higher elevations. Thus, increased arboreality with elevation at broad biogeographic scales mirrors patterns we observed at local scales. Our proposed ‘arboreality hypothesis’ suggests that the ability to exploit arboreal habitats confers the potential for larger geographical distributions because species can shift their location in the rainforest strata to compensate for shifts in temperature associated with elevation and latitude. This novel finding may help explain patterns of species richness and abundance wherever vegetation produces a vertical microclimatic gradient. Our results further suggest that global warming will ‘flatten’ the bio ersity in rainforests by pushing arboreal species towards the cooler and wetter ground. This ‘flattening’ could potentially have serious impacts on forest functioning and species survival.
Adapting to an invasive species: Toxic cane toads induce morphological change in Australian snakes
Publisher: Proceedings of the National Academy of Sciences
Date: 29-11-2004
Abstract: The arrival of invasive species can devastate natural ecosystems, but the long-term effects of invasion are less clear. If native organisms can adapt to the presence of the invader, the severity of impact will decline with time. In Australia, invasive cane toads ( Bufo marinus ) are highly toxic to most snakes that attempt to eat them. Because snakes are gape-limited predators with strong negative allometry for head size, maximum relative prey mass (and thus, the probability of eating a toad large enough to be fatal) decreases with an increase in snake body size. Thus, the arrival of toads should exert selection on snake morphology, favoring an increase in mean body size and a decrease in relative head size. We tested these predictions with data from specimens of four species of Australian snakes, collected over years. Geographic information system layers provided data on the duration of toad exposure for each snake population, as well as environmental variables (latitude, precipitation, and temperature). As predicted, two toad-vulnerable species ( Pseudechis porphyriacus and Dendrelaphis punctulatus ) showed a steady reduction in gape size and a steady increase in body length with time since exposure to toads. In contrast, two species at low risk from toads ( Hemiaspis signata and Tropidonophis mairii ) showed no consistent change in these morphological traits as a function of the duration of toad exposure. These results provide strong evidence of adaptive changes in native predators as a result of the invasion of toxic prey.
Species-isolating mechanisms in a mating system with male mate choice (garter snakes, Thamnophis spp.)
Publisher: Canadian Science Publishing
Date: 07-2004
DOI: 10.1139/Z04-086
Abstract: Reproductive isolation between sympatric taxa can be maintained by specific mate-recognition behaviours or by ecological ergence that reduces interspecific contact during reproduction. Common garter snakes, Thamnophis sirtalis (L., 1758), and plains garter snakes, Thamnophis radix (Baird and Girard, 1853), are sympatric over large areas, but morphological data suggest that the prezygotic isolation between these two species partially breaks down in a severely cold part of their joint range in Manitoba. Courtship trials show that male T. radix court intensely over a narrower range of (higher) ambient temperatures than do male T. sirtalis. Males selectively court females of their own species, but male T. radix are less choosy than male T. sirtalis. Hexane extracts of female skin lipids also elicited species-specific courtship. Although this male preference for species-specific pheromones contributes to species isolation, it is not strong enough to completely separate the two taxa. The absence of hybridization over most of the sympatric range may depend on the timing of mating (early spring, near the hibernation den). Differences between the species in hibernation-site selection and the timing of spring emergence break down in central Manitoba because severely cold winter temperatures force both species together into the few available hibernation (and thus, mating) sites, and the short warm season reduces temporal separation in emergence (and thus, mating) seasons.
Evolutionary processes make invasion speed difficult to predict
Publisher: Springer Science and Business Media LLC
Date: 10-02-2015
Predator behaviour and morphology mediates the impact of an invasive species: Cane toads and death adders in Australia
Publisher: Wiley
Date: 2010
Targeted gene flow for conservation
Publisher: Wiley
Date: 23-11-2016
DOI: 10.1111/COBI.12623
Abstract: Anthropogenic threats often impose strong selection on affected populations, causing rapid evolutionary responses. Unfortunately, these adaptive responses are rarely harnessed for conservation. We suggest that conservation managers pay close attention to adaptive processes and geographic variation, with an eye to using them for conservation goals. Translocating pre-adapted in iduals into recipient populations is currently considered a potentially important management tool in the face of climate change. Targeted gene flow, which involves moving in iduals with favorable traits to areas where these traits would have a conservation benefit, could have a much broader application in conservation. Across a species' range there may be long-standing geographic variation in traits or variation may have rapidly developed in response to a threatening process. Targeted gene flow could be used to promote natural resistance to threats to increase species resilience. We suggest that targeted gene flow is a currently underappreciated strategy in conservation that has applications ranging from the management of invasive species and their impacts to controlling the impact and virulence of pathogens.
Invader immunology: Invasion history alters immune system function in cane toads (Rhinella marina) in tropical Australia
Publisher: Wiley
Date: 14-11-2015
DOI: 10.1111/ELE.12390
Abstract: Because an in idual's investment into the immune system may modify its dispersal rate, immune function may evolve rapidly in an invader. We collected cane toads (Rhinella marina) from sites spanning their 75-year invasion history in Australia, bred them, and raised their progeny in standard conditions. Evolved shifts in immune function should manifest as differences in immune responses among the progeny of parents collected in different locations. Parental location did not affect the offspring's cell-mediated immune response or stress response, but blood from the offspring of invasion-front toads had more neutrophils, and was more effective at phagocytosis and killing bacteria. These latter measures of immune function are negatively correlated with rate of dispersal in free-ranging toads. Our results suggest that the invasion of tropical Australia by cane toads has resulted in rapid genetically based compensatory shifts in the aspects of immune responses that are most compromised by the rigours of long-distance dispersal.
Not such silly sausages: Evidence suggests northern quolls exhibit aversion to toads after training with toad sausages
Publisher: Wiley
Date: 13-03-2018
DOI: 10.1111/AEC.12595
The cane toad's (Chaunus [Bufo] marinus) increasing ability to invade Australia is revealed by a dynamically updated range model
Publisher: The Royal Society
Date: 27-03-2007
Abstract: Invasive species threaten biological ersity throughout the world. Understanding the dynamics of their spread is critical to mitigating this threat. In Australia, efforts are underway to control the invasive cane toad ( Chaunus [ Bufo ] marinus ). Range models based on their native bioclimatic envelope suggest that the cane toad is nearing the end of its invasion phase. However, such models assume a conserved niche between native and invaded regions and the absence of evolution to novel habitats. Here, we develop a dynamically updated statistical model to predict the growing extent of cane toad range based on their current distribution in Australia. Results demonstrate that Australian cane toads may already have the ability to spread across an area that almost doubles their current range and that triples projections based on their native distribution. Most of the expansion in suitable habitat area has occurred in the last decade and in regions characterized by high temperatures. Increasing use of extreme habitats may indicate that novel ecological conditions have facilitated a broader realized niche or that toad populations at the invasion front have evolved greater tolerance to extreme abiotic conditions. Rapid evolution to novel habitats combined with ecological release from native enemies may explain why some species become highly successful global invaders. Predicting species ranges following invasion or climate change may often require dynamically updated range models that incorporate a broader realization of niches in the absence of natural enemies and evolution in response to novel habitats.
Adjusting to a toxic invader: native Australian frogs learn not to prey on cane toads
Publisher: Oxford University Press (OUP)
Date: 2010
Rapid shifts in dispersal behavior on an expanding range edge Tom
Publisher: Proceedings of the National Academy of Sciences
Date: 29-07-2013
Abstract: Dispersal biology at an invasion front differs from that of populations within the range core, because novel evolutionary and ecological processes come into play in the nonequilibrium conditions at expanding range edges. In a world where species’ range limits are changing rapidly, we need to understand how in iduals disperse at an invasion front. We analyzed an extensive dataset from radio-tracking invasive cane toads ( Rhinella marina ) over the first 8 y since they arrived at a site in tropical Australia. Movement patterns of toads in the invasion vanguard differed from those of in iduals in the same area postcolonization. Our model discriminated enc ed versus dispersive phases within each toad’s movements and demonstrated that pioneer toads spent longer periods in dispersive mode and displayed longer, more directed movements while they were in dispersive mode. These analyses predict that overall displacement per year is more than twice as far for toads at the invasion front compared with those tracked a few years later at the same site. Studies on established populations (or even those a few years postestablishment) thus may massively underestimate dispersal rates at the leading edge of an expanding population. This, in turn, will cause us to underpredict the rates at which invasive organisms move into new territory and at which native taxa can expand into newly available habitat under climate change.
Not such silly sausages: Northern quolls exhibit aversion to toads after training with toad sausages
Publisher: Cold Spring Harbor Laboratory
Date: 26-08-2017
DOI: 10.1101/181149
Abstract: The invasion of toxic cane toads ( Rhinella marina ) is a major threat to northern quolls ( Dasyurus hallucatus ) which are poisoned when they attack this novel prey item. Quolls are now endangered as a consequence of the toad invasion. Conditioned taste aversion can be used to train in idual quolls to avoid toads, but we currently lack a training technique that can be used at a landscape scale to buffer entire populations from toad impact. Broad scale deployment requires a bait that can be used for training, but there is no guarantee that such a bait will ultimately elicit aversion to toads. Here we test a manufactured bait—a ‘toad sausage’—for its ability to elicit aversion to toads in northern quolls. To do this, we exposed one group of quolls to a toad sausage and another to a control sausage and compared the quolls’ predatory responses when presented with a dead adult toad. Captive quolls that consumed a single toad sausage showed substantially reduced interest in cane toads, interacting with them for less than half the time of their untrained counterparts and showing substantially reduced attack behaviour. We also quantified bait uptake in the field, by both quolls and non-target species. These field trials showed that wild quolls were the most frequent species attracted to the baits, and that approximately 61% of quolls consumed toad-aversion baits when first encountered. Between 40-68% of these animals developed aversion to further bait consumption. Our results suggest that toad-aversion sausages can be used to train wild quolls to avoid cane toads. This opens the possibility for broad-scale quoll training with toad aversion sausages: a technique that may allow wildlife managers to prevent quoll extinctions at a landscape scale.
Asplenium bird’s nest ferns in rainforest canopies are climate-contingent refuges for frogs
Publisher: Elsevier BV
Date: 12-2014
Improved spatial estimates of climate predict patchier species distributions
Publisher: Wiley
Date: 20-03-2013
DOI: 10.1111/DDI.12068
Intraspecific variation in climate-relevant traits in a tropical rainforest lizard
Publisher: Wiley
Date: 09-08-2016
DOI: 10.1111/DDI.12466
Effects of an invasive anuran the cane toad (Bufo marinus) on the invertebrate fauna of a tropical Australian floodplain
Publisher: Wiley
Date: 18-07-2006
Using Biophysical Models to Improve Survey Efficiency for Cryptic Ectotherms
Publisher: Wiley
Date: 13-06-2020
DOI: 10.1002/JWMG.21890
Trophic cascade driven by behavioural fine-tuning as naïve prey rapidly adjust to a novel predator
Publisher: Cold Spring Harbor Laboratory
Date: 27-11-2019
DOI: 10.1101/856997
Abstract: The arrival of novel predators can trigger trophic cascades driven by shifts in prey numbers. Predators also elicit behavioural change in prey populations, via phenotypic plasticity and/or rapid evolution, and such changes may also contribute to trophic cascades. Here we document rapid demographic and behavioural changes in populations of a prey species (grassland melomys Melomys burtoni , a granivorous rodent) following the introduction of a novel marsupial predator (northern quoll Dasyurus hallucatus ). Within months of quolls appearing, populations of melomys exhibited reduced survival and population declines relative to control populations. Quoll-invaded populations ( n = 4) were also significantly shyer than nearby, quoll-free populations ( n = 3) of conspecifics. This rapid but generalised response to a novel threat was replaced over the following two years with more threat-specific antipredator behaviours (i.e. predator-scent aversion). Predator-exposed populations, however, remained more neophobic than predator-free populations throughout the study. These behavioural responses manifested rapidly in avoidance of seeds associated with quoll scent, with discrimination playing out over a spatial scale of tens of metres. Presumably the significant and novel predation pressure induced by quolls drove melomys populations to fine-tune behavioural responses to be more predator-specific through time. These behavioural shifts could reflect in idual plasticity (phenotypic flexibility) in behaviour or may be adaptive shifts from natural selection imposed by quoll predation. Our study provides a rare insight into the rapid ecological and behavioural shifts enacted by prey to mitigate the impacts of a novel predator and shows that trophic cascades can be strongly influenced by behavioural changed rates of seed predation by melomys across treatments. Quoll-invaded melomys populations exhibited lower per-capita seed take rates, and rapidly developed an as well as numerical responses.
Unwelcome and unpredictable: The sorry saga of cane toads in Australia
Publisher: Cambridge University Press
Date: 22-12-2014
Forecasting species range dynamics with process‐explicit models: matching methods to applications
Publisher: Wiley
Date: 29-07-2019
DOI: 10.1111/ELE.13348
Abstract: Knowing where species occur is fundamental to many ecological and environmental applications. Species distribution models (SDMs) are typically based on correlations between species occurrence data and environmental predictors, with ecological processes captured only implicitly. However, there is a growing interest in approaches that explicitly model processes such as physiology, dispersal, demography and biotic interactions. These models are believed to offer more robust predictions, particularly when extrapolating to novel conditions. Many process-explicit approaches are now available, but it is not clear how we can best draw on this expanded modelling toolbox to address ecological problems and inform management decisions. Here, we review a range of process-explicit models to determine their strengths and limitations, as well as their current use. Focusing on four common applications of SDMs - regulatory planning, extinction risk, climate refugia and invasive species - we then explore which models best meet management needs. We identify barriers to more widespread and effective use of process-explicit models and outline how these might be overcome. As well as technical and data challenges, there is a pressing need for more thorough evaluation of model predictions to guide investment in method development and ensure the promise of these new approaches is fully realised.
Abiotic and biotic influences on the dispersal behavior of metamorph cane toads (Bufo marinus) in tropical Australia
Publisher: Wiley
Date: 2008
DOI: 10.1002/JEZ.450
Abstract: A mechanistic understanding of factors influencing the dispersal behavior of metamorph cane toads (Bufo marinus) has direct conservation relevance in Australia. These invasive anurans are toxic to native predators, and if we can predict their distribution across the landscape, we can also predict (and perhaps, manage) the scale of their impact. We propose that the major drivers of metamorph distribution are the risk of dehydration (restricting the young toads to moist substrates near pond margins) and biotic advantages to dispersal away from the pond (especially, less risk of cannibalism). To test this model, we investigated the influence of abiotic and biotic cues on the behavior of in idual toads in the laboratory. Substrate moisture levels strongly influenced metamorph activity levels and habitat selection: dry substrates induced most metamorphs to remain near water. The only biotic cue to influence metamorph dispersal was proximity of a larger (cannibalistic) conspecific a cannibal's presence at the pond margin caused most metamorphs to spend less time there, and as a consequence, to dehydrate more rapidly. Our results suggest that the spatial and temporal distribution of metamorph cane toads reflects a trade-off between competing risks: the danger of desiccation tends to keep young toads close to the pond margin in dry conditions, whereas the danger of cannibalism stimulates dispersal.
Behavioural responses of reptile predators to invasive cane toads in tropical Australia
Publisher: Wiley
Date: 11-2014
DOI: 10.1111/AEC.12102
The genetic backburn: using rapid evolution to halt invasions
Publisher: The Royal Society
Date: 24-02-2016
Abstract: The impact of an invasive species depends upon the extent of area across which it ultimately spreads. A powerful strategy for limiting impact, then, is to limit spread, and this can most easily be achieved by managing or reinforcing natural barriers to spread. Using a simulation model, we show that rapid evolutionary increases in dispersal can render permeable an otherwise effective barrier. On the other hand, we also show that, once the barrier is reached, and if it holds, resultant evolutionary decreases in dispersal rapidly make the barrier more effective. Finally, we sketch a strategy—the genetic backburn—in which low-dispersal in iduals from the range core are translocated to the nearside of the barrier ahead of the oncoming invasion. We find that the genetic backburn—by preventing invasion front genotypes reaching the barrier, and hastening the evolutionary decrease in dispersal—can make barriers substantially more effective. In our simulations, the genetic backburn never reduced barrier strength, however, the improvement to barrier strength was negligible when there was substantial long-distance dispersal, or when there was no genetic variation for dispersal distance. The improvement in barrier strength also depended on the trade-off between dispersal and competitive ability, with a stronger trade-off conferring greater power to the genetic backburn.
Evolution of dispersal and life history interact to drive accelerating spread of an invasive species
Publisher: Wiley
Date: 07-2013
DOI: 10.1111/ELE.12136
Abstract: Populations on the edge of an expanding range are subject to unique evolutionary pressures acting on their life-history and dispersal traits. Empirical evidence and theory suggest that traits there can evolve rapidly enough to interact with ecological dynamics, potentially giving rise to accelerating spread. Nevertheless, which of several evolutionary mechanisms drive this interaction between evolution and spread remains an open question. We propose an integrated theoretical framework for partitioning the contributions of different evolutionary mechanisms to accelerating spread, and we apply this model to invasive cane toads in northern Australia. In doing so, we identify a previously unrecognised evolutionary process that involves an interaction between life-history and dispersal evolution during range shift. In roughly equal parts, life-history evolution, dispersal evolution and their interaction led to a doubling of distance spread by cane toads in our model, highlighting the potential importance of multiple evolutionary processes in the dynamics of range expansion.
Single copy nuclear DNA markers characterized for comparative phylogeography in Australian wet tropics rainforest skinks
Publisher: Wiley
Date: 16-02-2004
Toad on the road: Use of roads as dispersal corridors by cane toads (Bufo marinus) at an invasion front in tropical Australia
Publisher: Elsevier BV
Date: 11-2006
Benefits of female mimicry in snakes
Publisher: Springer Science and Business Media LLC
Date: 11-2001
DOI: 10.1038/35104687
When dinner is dangerous: Toxic frogs elicit species-specific responses from a generalist snake predator
Publisher: University of Chicago Press
Date: 12-2007
DOI: 10.1086/522845
Abstract: In arms races between predators and prey, some evolved tactics are unbeatable by the other player. For ex le, many types of prey are inedible because they have evolved chemical defenses. In this case, prey death removes any selective advantage of toxicity to the prey but not the selective advantage to a predator of being able to consume the prey. In the absence of effective selection for postmortem persistence of the toxicity then, some chemical defenses probably break down rapidly after prey death. If so, predators can overcome the toxic defense simply by waiting for that breakdown before consuming the prey. Floodplain death adders (Acanthophis praelongus) are highly venomous frog-eating elapid snakes native to northern Australia. Some of the frogs they eat are nontoxic (Litoria nasuta), others produce gluelike mucus when seized by a predator (Limnodynastes convexiusculus), and one species (Litoria dahlii) is dangerously toxic to snakes. Both the glue and the toxin degrade within about 20 min of prey death. Adders deal with these prey types in different and highly stereotyped ways: they consume nontoxic frogs directly but envenomate and release the other taxa, waiting until the chemical defense loses its potency before consuming the prey.
An evolutionary process that assembles phenotypes through space rather than through time
Publisher: Proceedings of the National Academy of Sciences
Date: 21-03-2011
Abstract: In classical evolutionary theory, traits evolve because they facilitate organismal survival and/or reproduction. We discuss a different type of evolutionary mechanism that relies upon differential dispersal. Traits that enhance rates of dispersal inevitably accumulate at expanding range edges, and assortative mating between fast-dispersing in iduals at the invasion front results in an evolutionary increase in dispersal rates in successive generations. This cumulative process (which we dub “spatial sorting”) generates novel phenotypes that are adept at rapid dispersal, irrespective of how the underlying genes affect an organism's survival or its reproductive success. Although the concept is not original with us, its revolutionary implications for evolutionary theory have been overlooked. A range of biological phenomena (e.g., acceleration of invasion fronts, insular flightlessness, preadaptation) may have evolved via spatial sorting as well as (or rather than) by natural selection, and this evolutionary mechanism warrants further study.
Trophic cascade driven by behavioral fine-tuning as naïve prey rapidly adjust to a novel predator
Publisher: Wiley
Date: 03-06-2021
DOI: 10.1002/ECY.3363
Abstract: The arrival of novel predators can trigger trophic cascades driven by shifts in prey numbers. Predators also elicit behavioral change in prey populations, via phenotypic plasticity and/or rapid evolution, and such changes may also contribute to trophic cascades. Here, we document rapid demographic and behavioral changes in populations of a prey species (grassland melomys Melomys burtoni , a granivorous rodent) following the introduction of a novel marsupial predator (northern quoll Dasyurus hallucatus ). Within months of quolls appearing, populations of melomys exhibited reduced survival and population declines relative to control populations. Quoll‐invaded populations were also significantly shyer than nearby, quoll‐free populations of conspecifics. This rapid but generalized response to a novel threat was replaced over the following 2 yr with more threat‐specific antipredator behaviors (i.e., predator‐scent aversion). Predator‐exposed populations, however, remained more neophobic than predator‐free populations throughout the study. These behavioral responses manifested rapidly in changed rates of seed predation by melomys across treatments. Quoll‐invaded melomys populations exhibited lower per‐capita seed take rates, and rapidly developed an avoidance of seeds associated with quoll scent, with discrimination playing out over a spatial scale of tens of meters. Presumably the significant and novel predation pressure induced by quolls drove melomys populations to fine‐tune behavioral responses to be more predator specific through time. These behavioral shifts could reflect in idual plasticity (phenotypic flexibility) in behavior or may be adaptive shifts from natural selection imposed by quoll predation. Our study provides a rare insight into the rapid ecological and behavioral shifts enacted by prey to mitigate the impacts of a novel predator and shows that trophic cascades can be strongly influenced by behavioral as well as numerical responses.
A native dasyurid predator (common planigale, Planigale maculata) rapidly learns to avoid a toxic invader
Publisher: Wiley
Date: 08-10-2008
Slow and steady wins the race: spatial and stochastic processes and the failure of suppression gene drives
Publisher: Wiley
Date: 22-07-2022
DOI: 10.1111/MEC.16598
Abstract: Gene drives that skew sex ratios offer a new management tool to suppress or eradicate pest populations. Early models and empirical work suggest that these suppression drives can completely eradicate well‐mixed populations, but models that incorporate stochasticity and space (i.e. drift and recolonization events) often result in loss or failure of the drive. We developed a stochastic model to examine these processes in a simple one‐dimensional space. This simple space allows us to map the events and outcomes that emerged and examine how properties of the drive's wave of invasion affect outcomes. Our simulations, across a biologically realistic section of parameter space, suggest that drive failure might be a common outcome in spatially explicit, stochastic systems, and that properties of the drive wave appear to mediate outcomes. Surprisingly, the drives that would be considered fittest in an aspatial model were strongly associated with failure in the spatial setting. The fittest drives cause relatively fast moving, and narrow waves that have a high chance of being penetrated by wild‐types (WTs) leading to WT recolonization, leading to failure. Our results also show that high rates of dispersal reduce the chance of failure because drive waves get disproportionately wider than WT waves as dispersal rates increase. Overall, wide, slow‐moving drive waves were much less prone to failure. Our results point to the complexity inherent in using a genetic system to effect demographic outcomes and speak to a clear need for ecological and evolutionary modelling to inform the drive design process.
The evolution of an ‘intelligent’ dispersal strategy: biased, correlated random walks in patchy landscapes
Publisher: Wiley
Date: 28-01-2009
Does desiccation risk drive the distribution of juvenile cane toads (Bufo marinus) in tropical Australia?
Publisher: Cambridge University Press (CUP)
Date: 03-2009
DOI: 10.1017/S0266467408005695
Abstract: Immediately after their transition from aquatic to terrestrial life, juveniles of many anuran species are restricted to the margins of natal ponds. Understanding the factors determining the duration of that pondside aggregation has direct management ramifications in the case of the invasive cane toad ( Bufo marinus ) in tropical Australia. Previous work suggests that dispersal confers biotic advantages (reduced risk of cannibalism, enhanced feeding opportunities) to juvenile toads, but desiccation risk constrains these small animals to the moist margins of the pond. If so, juvenile dispersal should be sensitive to fluctuating hydric conditions on a diel and seasonal cycle. We tested this prediction with field observations (monitoring of dispersal to and from the pond) and field experiments (manipulating hydric regimes). Our results support a dynamic model of juvenile distribution, with a primary role for temporal variations in desiccation risk as the primary factor driving dispersal. During the dry season, strong diel cycles in desiccation risk generate a ‘tidal’ flow of juveniles, dispersing out in the moist morning but retreating to the pond margins at midday. Dispersal rates were enhanced by artificial watering during the dry season, and by the onset of the wet season.
Going feral: Time and propagule pressure determine range expansion of Asian house geckos into natural environments
Publisher: Wiley
Date: 14-09-2017
DOI: 10.1111/AEC.12416
Invasion, stress, and spinal arthritis in cane toads
Publisher: Proceedings of the National Academy of Sciences
Date: 06-11-2007
Abstract: The impact of invasive species on bio ersity has attracted considerable study, but impacts of the invasion process on the invaders themselves remain less clear. Invading species encounter conditions different from those in their ancestral habitats and are subject to intense selection for rapid dispersal. The end result may be significant stress on in idual organisms, with consequent health problems. Our studies on invasive cane toads in Australia reveal severe spinal arthritis in ≈10% of large adult toads, associated with the same factors (large body size, frequent movement, and relatively long legs) that have enabled toads to invade so rapidly across the Australian tropics.
Assessing the potential impact of cane toads on Australian snakes
Publisher: Wiley
Date: 12-2003
Sublethal costs associated with the consumption of toxic prey by snakes
Publisher: Wiley
Date: 16-03-2009
Directional dispersal has not evolved during the cane toad invasion
Publisher: Wiley
Date: 12-01-2015
Cane toads lack physiological enhancements for dispersal at the invasive front in Northern Australia
Publisher: The Company of Biologists
Date: 02-11-2011
DOI: 10.1242/BIO.2011024
Abstract: Many invasive species have evolved behavioural and morphological characteristics that facilitate their dispersal into new areas, but it is unclear how selection on this level of the phenotype filters through to the underlying physiology. Cane toads have been dispersing westward across northern tropical Australia for more than 70 years. Previous studies of cane toads at the invasive front have identified several behavioural, morphological and locomotory characteristics that have evolved to facilitate dispersal of toads. We assessed a range of physiological characteristics associated with locomotory abilities in toads from the long-established, east coast of Australia, from the invasive front, and from a site in between these locations. We measured time to exhaustion and respiratory gases of toads exercising on a treadmill, time to recovery from exhaustion, blood properties (lactate, haematocrit, haemoglobin, red blood cell count, blood cell volume), and muscle properties associated with locomotion (activities of the enzymes citrate synthase and lactate dehydrogenase, and pH buffering capacity). None of the measured physiological parameters supported the hypothesis that toads from the invasive front possess physiological adaptations that facilitate dispersal compared to toads from areas colonised in the past. The strongest difference among the three groups of toads, time to exhaustion, showed exactly the opposite trend toads from the long-established populations in the east coast had the longest time to exhaustion. Successful colonisers can employ many characteristics to facilitate their dispersal, so the extent to which behaviour, morphology and physiology co-evolve remains an interesting question. However, in the present case at least, behavioural adaptations do not appear to have altered the organism's underlying physiology.
Life-history evolution in range-shifting populations
Publisher: Wiley
Date: 06-2010
DOI: 10.1890/09-0910.1
Abstract: Most evolutionary theory does not deal with populations expanding or contracting in space. Invasive species, climate change, epidemics, and the breakdown of dispersal barriers, however, all create populations in this kind of spatial disequilibrium. Importantly, spatial disequilibrium can have important ecological and evolutionary outcomes. During continuous range expansion, for ex le, populations on the expanding front experience novel evolutionary pressures because frontal populations are assorted by dispersal ability and have a lower density of conspecifics than do core populations. These conditions favor the evolution of traits that increase rates of dispersal and reproduction. Additionally, lowered density on the expanding front eventually frees populations on the expanding edge from specialist, coevolved enemies, permitting higher investment into traits associated with dispersal and reproduction rather than defense against pathogens. As a result, the process of range expansion drives rapid life-history evolution, and this seems to occur despite ongoing serial founder events that have complex effects on genetic ersity at the expanding front. Traits evolving on the expanding edge are smeared across the landscape as the front moves through, leaving an ephemeral signature of range expansion in the life-history traits of a species across its newly colonized range. Recent studies suggest that such nonequilibrium processes during recent population history may have contributed to many patterns usually ascribed to evolutionary forces acting in populations at spatial equilibrium.
Parasites and pathogens lag behind their host during periods of host range advance
Publisher: Wiley
Date: 03-2010
DOI: 10.1890/09-0530.1
Abstract: The process of rapid range expansion (as seen in many invasive species, and in taxa responding to climate change) may substantially disrupt host-parasite dynamics. Parasites and pathogens can have strong regulatory effects on their host population and, in doing so, exert selection pressure on host life history. We construct a simple in idual-based model of host-parasite dynamics during range expansion. This model shows that the parasites and pathogens of a range-expanding host are likely to be absent from the host's invasion front, because stochastic events (serial founder events) in low-density frontal populations result in local extinctions or transmission failure of the parasite athogen and, hence, a preponderance of uninfected hosts in the invasion vanguard. This pattern is true for both density-dependent and density-independent transmission rates, although it is exacerbated in the case of density-dependent transmission because, in this case, transmission rates also decline on the front. Data from field surveys on the prevalence of lungworms (Rhabdias pseudosphaerocephala) in invasive cane toads (Bufo marinus) support these predictions, in showing that toads in newly invaded areas of tropical Australia lack the parasite, which only arrives 1-3 years after the toads themselves. The resultant "honeymoon phase" immediately post-invasion, when in iduals in the invasion-front population are virtually pathogen-free, may lead to altered host population dynamics on the invasion front, causing, for ex le, high densities in invasion-front populations, followed by a decline in numbers as parasites and pathogens arrive and begin to reduce host viability. The honeymoon phase may ultimately impact the evolution of life-history investment strategies in both host and parasite on the invasion vanguard, as hosts are released from immune challenges and parasites continuously expand into a favorable and unoccupied niche.
Targeted gene flow and rapid adaptation in an endangered marsupial
Publisher: Wiley
Date: 04-09-2018
DOI: 10.1111/COBI.13149
Abstract: Targeted gene flow is an emerging conservation strategy. It involves translocating in iduals with favorable genes to areas where they will have a conservation benefit. The applications for targeted gene flow are wide-ranging but include preadapting native species to the arrival of invasive species. The endangered carnivorous marsupial, the northern quoll (Dasyurus hallucatus), has declined rapidly since the introduction of the cane toad (Rhinella marina), which fatally poisons quolls that attack them. There are, however, a few remaining toad-invaded quoll populations in which the quolls survive because they know not to eat cane toads. It is this toad-smart behavior we hope to promote through targeted gene flow. For targeted gene flow to be feasible, however, toad-smart behavior must have a genetic basis. To assess this, we used a common garden experiment, comparing offspring from toad-exposed and toad-naïve parents raised in identical environments, to determine whether toad-smart behavior is heritable. Offspring from toad-exposed populations were substantially less likely to eat toads than those with toad-naïve parents. Hybrid offspring showed similar responses to quolls with 2 toad-exposed parents, indicating the trait may be dominant. Together, these results suggest a heritable trait and rapid adaptive response in a small number of toad-exposed populations. Although questions remain about outbreeding depression, our results are encouraging for targeted gene flow. It should be possible to introduce toad-smart behavior into soon to be affected quoll populations.
The ecological impact of invasive cane toads on tropical snakes: Field data do not support laboratory-based predictions
Publisher: Wiley
Date: 02-2011
DOI: 10.1890/10-0536.1
Abstract: Predicting which species will be affected by an invasive taxon is critical to developing conservation priorities, but this is a difficult task. A previous study on the impact of invasive cane toads (Bufo marinus) on Australian snakes attempted to predict vulnerability a priori based on the assumptions that any snake species that eats frogs, and is vulnerable to toad toxins, may be at risk from the toad invasion. We used time-series analyses to evaluate the accuracy of that prediction, based on >3600 standardized nocturnal surveys over a 138-month period on 12 species of snakes and lizards on a floodplain in the Australian wet-dry tropics, bracketing the arrival of cane toads at this site. Contrary to prediction, encounter rates with most species were unaffected by toad arrival, and some taxa predicted to be vulnerable to toads increased rather than declined (e.g., death adder Acanthophis praelongus Children's python Antaresia childreni). Indirect positive effects of toad invasion (perhaps mediated by toad-induced mortality of predatory varanid lizards) and stochastic weather events outweighed effects of toad invasion for most snake species. Our study casts doubt on the ability of a priori desktop studies, or short-term field surveys, to predict or document the ecological impact of invasive species.
Modelling species distributions without using species distributions: the cane toad in Australia under current and future climates
Publisher: Wiley
Date: 08-2008
Identifying optimal barriers to halt the invasion of cane toads Rhinella marina in arid Australia
Publisher: Wiley
Date: 12-12-2013
The spatial ecology of cane toads (Bufo marinus) in tropical Australia: Why do metamorph toads stay near the water?
Publisher: Wiley
Date: 04-07-2008
The capacity of refugia for conservation planning under climate change
Publisher: Wiley
Date: 03-2015
DOI: 10.1890/140055
No outbreeding depression in a trial of targeted gene flow in an endangered Australian marsupial
Publisher: Springer Science and Business Media LLC
Date: 20-10-2020
Do pathogens become more virulent as they spread? Evidence from the amphibian declines in Central America
Publisher: The Royal Society
Date: 07-09-2013
Abstract: The virulence of a pathogen can vary strongly through time. While cyclical variation in virulence is regularly observed, directional shifts in virulence are less commonly observed and are typically associated with decreasing virulence of biological control agents through coevolution. It is increasingly appreciated, however, that spatial effects can lead to evolutionary trajectories that differ from standard expectations. One such possibility is that, as a pathogen spreads through a naive host population, its virulence increases on the invasion front. In Central America, there is compelling evidence for the recent spread of pathogenic Batrachochytrium dendrobatidis (Bd) and for its strong impact on hibian populations. Here, we re-examine data on Bd prevalence and hibian population decline across 13 sites from southern Mexico through Central America, and show that, in the initial phases of the Bd invasion, hibian population decline lagged approximately 9 years behind the arrival of the pathogen, but that this lag diminished markedly over time. In total, our analysis suggests an increase in Bd virulence as it spread southwards, a pattern consistent with rapid evolution of increased virulence on Bd's invading front. The impact of Bd on hibians might therefore be driven by rapid evolution in addition to more proximate environmental drivers.
Evolution transforms pushed waves into pulled waves
Publisher: Cold Spring Harbor Laboratory
Date: 15-02-2018
DOI: 10.1101/266007
Abstract: Understanding the dynamics of biological invasions is crucial for managing numerous phenomena, from invasive species to tumours. While Allee effects (where in iduals in low-density populations suffer lowered fitness) are known to influence both the ecological and evolutionary dynamics of invasions, the possibility that an invader’s susceptibility to the Allee effect might itself evolve on an invasion front has received almost no attention. Since invasion fronts are regions of perpetually low population density, selection should favour vanguard invaders that are resistant to Allee effects. Evolution in response to this pressure could cause invasions to transition from pushed waves, propelled by dispersal from behind the invasion front, to pulled waves, driven by the invasion vanguard. To examine this possibility, we construct an in idual-based model in which a trait that governs resistance to the Allee effect is allowed to evolve during an invasion. We find that vanguard invaders rapidly evolve resistance to the Allee effect, causing invasions to accelerate. This also results in invasions transforming from pushed waves into pulled waves, an outcome with consequences for predictions of invasion speed, the population’s genetic structure, and other important behaviours. These findings underscore the importance of accounting or evolution in invasion forecasts, and suggest that evolution has the capacity to fundamentally alter invasion dynamics.
Road transect surveys do not reveal any consistent effects of a toxic invasive species on tropical reptiles
Publisher: Springer Science and Business Media LLC
Date: 21-10-2013
Reduced investment in immune function in invasion-front populations of the cane toad (Rhinella marina) in Australia
Publisher: Springer Science and Business Media LLC
Date: 27-11-2012
How many, and when? Optimising targeted gene flow for a step change in the environment
Publisher: Cold Spring Harbor Laboratory
Date: 07-06-2018
DOI: 10.1101/341339
Abstract: Targeted gene flow is an emerging conservation strategy that involves translocating in iduals with particular traits to places where they are of benefit, thereby increasing a population’s evolutionary resilience. While the idea can work in theory, questions remain as to how best to implement it. Here, we vary timing of introduction and size of the introduced cohort to maximise our objective – survival of the recipient population’s genome. We demonstrate our approach using the northern quoll, an Australian marsupial predator threatened by the toxic cane toad. We highlight a general trade-off between maintaining a local genome and reducing population extinction risk, but show that key management levers can optimise this so that 100% of the population’s genome is preserved. In our case, any action was better than not acting at all (even with strong outbreeding depression), but the size of the benefit was sensitive to timing and size of the introduction.
Evolutionarily accelerated invasions: the rate of dispersal evolves upwards during the range advance of cane toads
Publisher: Wiley
Date: 07-10-2010
DOI: 10.1111/J.1420-9101.2010.02118.X
Abstract: Human activities are changing habitats and climates and causing species' ranges to shift. Range expansion brings into play a set of powerful evolutionary forces at the expanding range edge that act to increase dispersal rates. One likely consequence of these forces is accelerating rates of range advance because of evolved increases in dispersal on the range edge. In northern Australia, cane toads have increased their rate of spread fivefold in the last 70 years. Our breeding trials with toads from populations spanning the species' invasion history in Australia suggest a genetic basis to dispersal rates and interpopulation genetic variation in such rates. Toads whose parents were from the expanding range front dispersed faster than toads whose parents were from the core of the range. This difference reflects patterns found in their field-collected mothers and fathers and points to heritable variance in the traits that have accelerated the toads' rate of invasion across tropical Australia over recent decades. Taken together with demonstrated spatial assortment by dispersal ability occurring on the expanding front, these results point firmly to ongoing evolution as a driving force in the accelerated expansion of toads across northern Australia.
Reply to Lee: Spatial sorting, assortative mating, and natural selection
Publisher: Proceedings of the National Academy of Sciences
Date: 28-06-2011
May the (selective) force be with you: Spatial sorting and natural selection exert opposing forces on limb length in an invasive amphibian
Publisher: Wiley
Date: 30-07-2019
DOI: 10.1111/JEB.13504
Abstract: Spatial sorting on invasion fronts drives the evolution of dispersive phenotypes, and in doing so can push phenotypes in the opposite direction to natural selection. The invasion of cane toads (Rhinella marina) through tropical Australia has accelerated over recent decades because of the accumulation of dispersal-enhancing traits at the invasion front, driven by spatial sorting. One such trait is the length of the forelimbs: invasion-front toads have longer arms (relative to body length) in comparison with populations 10-20 years after invasion. Such a shift likely has fitness consequences: an increase of forearm length would decrease the strength with which a male could cling to a female during lexus and so render such a male less competitive in competition for mates, compared to short-armed conspecifics. Our laboratory trials of attachment strength confirmed that males with relatively longer arms were easier to displace, and competition trials show higher duration of lexus for males with shorter arms. Together with the sharp cline in limb length observed behind the invasion front, these results imply an opposition of selective forces: spatial sorting optimizes dispersal, but as this force wanes behind the invasion front, we see the primacy of natural selection reassert itself.
An invasive species imposes selection on life-history traits of a native frog
Publisher: Oxford University Press (OUP)
Date: 19-05-2010
Stress and immunity at the invasion front: a comparison across cane toad (Rhinella marina) populations
Publisher: Oxford University Press (OUP)
Date: 08-2015
DOI: 10.1111/BIJ.12623
Evolutionary processes make invasion speed difficult to predict
Publisher: Cold Spring Harbor Laboratory
Date: 11-01-2015
DOI: 10.1101/013680
Abstract: A capacity to predict the spread rate of populations is critical for understanding the impacts of climate change and invasive species. Despite sophisticated theory describing how populations spread, the prediction of spread rate remains a formidable challenge. As well as the inherent stochasticity in the spread process, spreading populations are subject to strong evolutionary forces (operating on dispersal and reproductive rates) that can cause accelerating spread. Despite these strong evolutionary forces, serial founder events and drift on the expanding range edge mean that evolutionary trajectories in the invasion vanguard may be highly stochastic. Here I develop a model of spatial spread in continuous space that incorporates evolution of continuous traits under a quantitative genetic model of inheritance. I use this model to investigate the potential role of evolution on the variation in spread rate between replicate model realisations. Models incorporating evolution exhibited more than four times the variance in spread rate across replicate invasions compared with non-evolving scenarios. Results suggest that the majority of this increase in variation is driven by evolutionary stochasticity on the invasion front rather than initial founder events: in many cases evolutionary stochasticity on the invasion front contributed more than 90% of the variance in spread rate over 30 generations. Our uncertainty around predicted spread rates -- whether for invasive species or those shifting under climate change -- may be much larger than we expect when the spreading population contains heritable variation in rates of dispersal and reproduction.
Range shift promotes the formation of stable range edges
Publisher: Wiley
Date: 07-09-2012
Out of the frying pan: Reintroduction of toad-smart northern quolls to southern Kakadu National Park
Publisher: Wiley
Date: 24-10-2018
DOI: 10.1111/AEC.12551
Stepping inside the niche: microclimate data are critical for accurate assessment of species' vulnerability to climate change
Publisher: The Royal Society
Date: 09-2014
Abstract: To assess a species' vulnerability to climate change, we commonly use mapped environmental data that are coarsely resolved in time and space. Coarsely resolved temperature data are typically inaccurate at predicting temperatures in microhabitats used by an organism and may also exhibit spatial bias in topographically complex areas. One consequence of these inaccuracies is that coarsely resolved layers may predict thermal regimes at a site that exceed species' known thermal limits. In this study, we use statistical downscaling to account for environmental factors and develop high-resolution estimates of daily maximum temperatures for a 36 000 km 2 study area over a 38-year period. We then demonstrate that this statistical downscaling provides temperature estimates that consistently place focal species within their fundamental thermal niche, whereas coarsely resolved layers do not. Our results highlight the need for incorporation of fine-scale weather data into species' vulnerability analyses and demonstrate that a statistical downscaling approach can yield biologically relevant estimates of thermal regimes.
Behavioral shifts associated with reproduction in garter snakes
Publisher: Oxford University Press (OUP)
Date: 03-2003
The frog filter: amphibian introduction bias driven by taxonomy, body size and biogeography
Publisher: Wiley
Date: 08-06-2010
Chemoreception and mating behaviour of a tropical Australian skink
Publisher: Springer Science and Business Media LLC
Date: 24-01-2015
Do invasive cane toads (Chaunus marinus) compete with Australian frogs (Cyclorana australis)?
Publisher: Wiley
Date: 06-11-2007
Invasion and the evolution of speed in toads
Publisher: Springer Science and Business Media LLC
Date: 02-2006
DOI: 10.1038/439803A
Abstract: Cane toads (Bufo marinus) are large anurans (weighing up to 2 kg) that were introduced to Australia 70 years ago to control insect pests in sugar-cane fields. But the result has been disastrous because the toads are toxic and highly invasive. Here we show that the annual rate of progress of the toad invasion front has increased about fivefold since the toads first arrived we find that toads with longer legs can not only move faster and are the first to arrive in new areas, but also that those at the front have longer legs than toads in older (long-established) populations. The disaster looks set to turn into an ecological nightmare because of the negative effects invasive species can have on native ecosystems over many generations, rates of invasion will be accelerated owing to rapid adaptive change in the invader, with continual 'spatial selection' at the expanding front favouring traits that increase the toads' dispersal.
Tails of enticement: caudal luring by an ambush-foraging snake ( Acanthophis praelongus , Elapidae)
Publisher: Wiley
Date: 03-11-2008
Anywhere but here: local conditions alone drive dispersal in Daphnia
Publisher: Cold Spring Harbor Laboratory
Date: 30-05-2018
DOI: 10.1101/334243
Abstract: Dispersal is fundamental to population dynamics and it is increasingly apparent that, despite most models treating dispersal as a constant, many organisms make dispersal decisions based upon information gathered from the environment. Ideally, organisms would make fully informed decisions, with knowledge of both intra-patch conditions (conditions in their current location) and extra-patch conditions (conditions in alternative locations). Acquiring information is energetically costly however, and extra-patch information will typically be costlier to obtain than intra-patch information. As a consequence, theory suggests that organisms will often make partially informed dispersal decisions, utilising intra-patch information only. We test this proposition in an experimental two-patch system using populations of the aquatic crustacean, Daphnia carinata . We manipulated conditions (food availability) in the population’s home patch, and in its alternative patch. We found that D. carinata made use of intra-patch information (resource limitation in the home patch induced a ten-fold increase in dispersal probability) but made no use of extra-patch information (resource limitation in the alternative patch did not affect dispersal probability). Our work highlights the very large influence that information can have on dispersal probability, but also that dispersal decisions will often be made in only a partially informed manner. The magnitude of the response we observed also adds to the growing chorus that condition-dependence may be a significant driver of variation in dispersal.
Risky movement increases the rate of range expansion
Publisher: The Royal Society
Date: 28-09-2011
Abstract: The movement rules used by an in idual determine both its survival and dispersal success. Here, we develop a simple model that links inter-patch movement behaviour with population dynamics in order to explore how in idual dispersal behaviour influences not only its dispersal and survival, but also the population's rate of range expansion. Whereas dispersers are most likely to survive when they follow nearly straight lines and rapidly orient movement towards a non-natal patch, the most rapid rates of range expansion are obtained for trajectories in which in iduals delay biasing their movement towards a non-natal patch. This result is robust to the spatial structure of the landscape. Importantly, in a set of evolutionary simulations, we also demonstrate that the movement strategy that evolves at an expanding front is much closer to that maximizing the rate of range expansion than that which maximizes the survival of dispersers. Our results suggest that if one of our conservation goals is the facilitation of range-shifting, then current indices of connectivity need to be complemented by the development and utilization of new indices providing a measure of the ease with which a species spreads across a landscape.
Rapid evolution in predator-free conservation havens and its effects on endangered species recovery
Publisher: Wiley
Date: 13-08-2021
DOI: 10.1111/COBI.13521
Fatal attraction: Adaptations to prey on native frogs imperil snakes after invasion of toxic toads
Publisher: The Royal Society
Date: 06-05-2009
Abstract: Adaptations that enhance fitness in one situation can become liabilities if circumstances change. In tropical Australia, native snake species are vulnerable to the invasion of toxic cane toads. Death adders ( Acanthophis praelongus ) are ambush foragers that (i) attract vertebrate prey by caudal luring and (ii) handle anuran prey by killing the frog then waiting until the frog's chemical defences degrade before ingesting it. These tactics render death adders vulnerable to toxic cane toads ( Bufo marinus ), because toads elicit caudal luring more effectively than do native frogs, and are more readily attracted to the lure. Moreover, the strategy of delaying ingestion of a toad after the strike does not prevent fatal poisoning, because toad toxins (unlike those of native frogs) do not degrade shortly after the prey dies. In our laboratory and field trials, half of the death adders died after ingesting a toad, showing that the specialized predatory behaviours death adders use to capture and process prey render them vulnerable to this novel prey type. The toads' strong response to caudal luring also renders them less fit than native anurans (which largely ignored the lure): all toads bitten by adders died. Together, these results illustrate the dissonance in behavioural adaptations that can arise following the arrival of invasive species, and reveal the strong selection that occurs when mutually naive species first interact.
Rapid expansion of the cane toad (Bufo marinus) invasion front in tropical Australia
Publisher: Wiley
Date: 05-03-2007
Do evolutionary constraints on thermal performance manifest at different organizational scales?
Publisher: Wiley
Date: 18-11-2014
DOI: 10.1111/JEB.12526
Abstract: The two foremost hypotheses on the evolutionary constraints on an organism's thermal sensitivity—the hotter-is-better expectation, and the specialist-generalist trade-off—have received mixed support from empirical studies testing for their existence. Could these conflicting results reflect confusion regarding the organizational level (i.e. species > population > in idual) at which these constraints should manifest? We propose that these evolutionary constraints should manifest at different organizational levels because of differences in their underlying causes and requirements. The hotter-is-better expectation should only manifest across separate evolutionary units (e.g. species, populations), and not within populations. The specialist-generalist trade-off, by contrast, should manifest within as well as between separate evolutionary units. We measured the thermal sensitivity of sprint performance for 440 rainforest sun skinks (L ropholis coggeri) representing 10 populations, and used the resulting performance curves to test for evidence for the hypothesized constraints at two organizational levels: (i) across populations and (ii) within populations. As predicted, the hotter-is-better expectation was evident only at the across-population level, whereas the specialist-generalist trade-off was evident within, as well as across, populations. Our results suggest that, depending on the processes that drive them, evolutionary constraints can manifest at different organizational levels. Consideration of these underlying processes, and the organizational level at which a constraint should manifest, may help resolve conflicting empirical results.
Stability of the wMel Wolbachia Infection following Invasion into Aedes aegypti Populations
Publisher: Public Library of Science (PLoS)
Date: 11-09-2014
Using connectivity to identify climatic drivers of local adaptation
Publisher: Cold Spring Harbor Laboratory
Date: 02-06-2017
DOI: 10.1101/145169
Abstract: This preprint has been reviewed and recommended by Peer Community In Evolutionary Biology ( 0.24072 ci.evolbiol.100034 ). Despite being able to conclusively demonstrate local adaptation, we are still often unable to objectively determine the climatic drivers of local adaptation. Given the rapid rate of global change, understanding the climatic drivers of local adaptation is vital. Not only will this tell us which climate axes matter most to population fitness, but such knowledge is critical to inform management strategies such as translocation and targeted gene flow. While simple assessments of geographic trait variation are useful, geographic variation (and its associations with environment) may represent plastic, rather than evolved, differences. Additionally, the vast number of trait–environment combinations makes it difficult to determine which aspects of the environment populations adapt to. Here we argue that by incorporating a measure of landscape connectivity as a proxy for gene flow, we can differentiate between trait–environment relationships underpinned by genetic differences versus those that reflect phenotypic plasticity. By doing so, we can rapidly shorten the list of trait–environment combinations that may be of adaptive significance. We demonstrate how this reasoning can be applied using data on geographic trait variation in a lizard species from Australia's Wet Tropics rainforest. Our analysis reveals an overwhelming signal of local adaptation for the traits and environmental variables we investigated. Our analysis also allows us to rank environmental variables by the degree to which they appear to be driving local adaptation. Although encouraging, methodological issues remain: we point to these issue in the hope that the community can rapidly hone the methods we sketch here. The promise is a rapid and general approach to identifying the environmental drivers of local adaptation.
The lexicon of love: What cues cause size-assortative courtship by male garter snakes?
Publisher: Springer Science and Business Media LLC
Date: 03-2003
Spatial Sorting Unlikely to Promote Maladaptive Hybridization: Response to Lowe, Muhlfeld, and Allendorf
Publisher: Elsevier BV
Date: 10-2015
Characteristics of climate change refugia for Australian biodiversity
Publisher: Wiley
Date: 05-05-2014
DOI: 10.1111/AEC.12146
Allometry and selection in a novel predator-prey system: Australian snakes and the invading cane toad
Publisher: Wiley
Date: 2006
Heat hardening in a tropical lizard: geographic variation explained by the predictability and variance in environmental temperatures
Publisher: Wiley
Date: 29-12-2016
Establishment Success of Introduced Amphibians Increases in the Presence of Congeneric Species
Publisher: University of Chicago Press
Date: 03-2011
DOI: 10.1086/658342
Abstract: Darwin's naturalization hypothesis predicts that the success of alien invaders will decrease with increasing taxonomic similarity to the native community. Alternatively, shared traits between aliens and the native assemblage may preadapt aliens to their novel surroundings, thereby facilitating establishment (the preadaptation hypothesis). Here we examine successful and failed introductions of hibian species across the globe and find that the probability of successful establishment is higher when congeneric species are present at introduction locations and increases with increasing congener species richness. After accounting for positive effects of congeners, residence time, and propagule pressure, we also find that invader establishment success is higher on islands than on mainland areas and is higher in areas with abiotic conditions similar to the native range. These findings represent the first ex le in which the preadaptation hypothesis is supported in organisms other than plants and suggest that preadaptation has played a critical role in enabling introduced species to succeed in novel environments.
A toad more traveled: The heterogeneous invasion dynamics of cane toads in Australia
Publisher: University of Chicago Press
Date: 03-2008
DOI: 10.1086/527494
Abstract: To predict the spread of invasive species, we need to understand the mechanisms that underlie their range expansion. Assuming random diffusion through homogeneous environments, invasions are expected to progress at a constant rate. However, environmental heterogeneity is expected to alter diffusion rates, especially by slowing invasions as populations encounter suboptimal environmental conditions. Here, we examine how environmental and landscape factors affect the local invasion speeds of cane toads (Chaunus [Bufo] marinus) in Australia. Using high-resolution cane toad data, we demonstrate heterogeneous regional invasion dynamics that include both decelerating and accelerating range expansions. Toad invasion speed increased in regions characterized by high temperatures, heterogeneous topography, low elevations, dense road networks, and high patch connectivity. Regional increases in the toad invasion rate might be caused by environmental conditions that facilitate toad reproduction and movement, by the evolution of long-distance dispersal ability, or by some combination of these factors. In any case, theoretical predictions that neglect environmental influences on dispersal at multiple spatial scales may prove to be inaccurate. Early predictions of cane toad range expansion rates that assumed constant diffusion across homogeneous landscapes already have been proved wrong. Future attempts to predict range dynamics for invasive species should consider heterogeneity in (1) the environmental factors that determine dispersal rates and (2) the mobility of invasive populations because dispersal-relevant traits can evolve in exotic habitats. As an invasive species spreads, it is likely to encounter conditions that influence dispersal rates via one or both of these mechanisms.
Spatial and temporal variation in the morphology (and thus, predicted impact) of an invasive species in Australia
Publisher: Wiley
Date: 22-12-2006
Invasion history alters the behavioural consequences of immune system activation in cane toads
Publisher: Wiley
Date: 28-02-2018
Abstract: Acute activation of the immune system often initiates a suite of behavioural changes. These "sickness behaviours"-involving lethargy and decreased activity-may be particularly costly on invasion fronts, where evolutionary pressures on dispersal favour in iduals that move large distances. We used a combination of field and laboratory studies to compare sickness behaviours of cane toads from populations differing in invasion history. To do this we stimulated immune system activation by injecting lipopolysaccharide (LPS) to mimic bacterial infection. We predicted that LPS would result in less severe sickness behaviour in toads from range-edge populations because they had undergone selection for rapid and sustained dispersal (activities in conflict with lethargy and decreased activity). Contrary to our prediction, LPS injection caused a greater reduction in dispersal-relevant traits in invasion-front in iduals than in conspecifics from the range-core. Our data suggest that the rapid invasion of cane toads through tropical Australia has seen an evolutionary shift in the magnitude of sickness behaviour elicited by pathogen infection. The increased sickness behaviour among range-edge toads suggests a shift away from pathogen tolerance (seen in range-core populations) towards resistance to pathogen attack. But as a consequence, when pathogens do become successfully established, toads from invasion-front populations may have less capacity to tolerate their ill-effects.
Related Organisations
University Of Sydney School Of Biological Sciences
Location: Australia
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