ORCID Profile
0000-0001-7529-5657
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
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)
Ecology | Terrestrial Ecology | Conservation And Biodiversity | Terrestrial Ecology | Life Histories (Incl. Population Ecology) | Environmental Science and Management | Invasive Species Ecology | Vertebrate Biology | Sociobiology And Behavioural Ecology | Biological Adaptation | Genetics | Evolutionary Biology | Freshwater Ecology | Ecological Applications | Global Change Biology | Ecology And Evolution Not Elsewhere Classified | Environmental Management And Rehabilitation | Wildlife And Habitat Management | Conservation | Epigenetics (incl. Genome Methylation and Epigenomics) | Population Ecology | Behavioural ecology | Conservation and Biodiversity | Marine And Estuarine Ecology (Incl. Marine Ichthyology) | Palaeoecology | Ecology | Archaeology Of Hunter-Gatherer Societies (Incl. Pleistocene | Evolutionary Impacts of Climate Change | Host-Parasite Interactions | Genetic Immunology | Evolutionary ecology |
ANZSRC Socio-Economic Objective (SEO)
Control of Pests, Diseases and Exotic Species at Regional or Larger Scales | Control of pests and exotic species | Living resources (flora and fauna) | Living resources (flora and fauna) | Control of Animal Pests, Diseases and Exotic Species in Forest and Woodlands Environments | Living resources (flora and fauna) | Integrated (ecosystem) assessment and management | Biological sciences | Flora, Fauna and Biodiversity at Regional or Larger Scales | Control of Pests, Diseases and Exotic Species in Fresh, Ground and Surface Water Environments | Control of pests and exotic species | Control of pests and exotic species | Environmental and resource evaluation not elsewhere classified | Climate change | Living resources (incl. impacts of fishing on non-target species) | Integrated (ecosystem) assessment and management | Control of Pests, Diseases and Exotic Species in Sparseland, Permanent Grassland and Arid Zone Environments | Forest and Woodlands Flora, Fauna and Biodiversity | Ecosystem Adaptation to Climate Change | Control of pests and exotic species | Living resources (flora and fauna) | Living resources (flora and fauna) | Expanding Knowledge in the Biological Sciences
Related Links
Publications
Behavioural divergence during biological invasions: a study of cane toads (Rhinella marina) from contrasting environments in Hawai'i
Publisher: The Royal Society
Date: 04-2018
DOI: 10.1098/RSOS.180197
Abstract: Invasive species must deal with novel challenges, both from the alien environment and from pressures arising from range expansion per se (e.g. spatial sorting). Those conditions can create geographical variation in behaviour across the invaded range, as has been documented across regions of Australia invaded by cane toads range-edge toads are more exploratory and willing to take risks than are conspecifics from the range-core. That behavioural ergence might be a response to range expansion and invasion per se , or to the different environments encountered. Climate differs across the cane toads' invasion range from the wet tropics of Queensland to the seasonally dry climates of northwestern Western Australia. The different thermal and hydric regimes may affect behavioural traits via phenotypic plasticity or through natural selection. We cannot tease apart the effects of range expansion versus climate in an expanding population but can do so in a site where the colonizing species was simultaneously released in all suitable areas, thus removing any subsequent phase of range expansion. Cane toads were introduced to Hawai'i in 1932 and thence to Australia in 1935. Toads were released in all major sugarcane-growing areas in Hawai'i within a 12-month period. Hence, Hawai'ian cane toads provide an opportunity to examine geographical ergence in behavioural traits in a climatically erse region (each island has both wet and dry sides) in the absence of range expansion subsequent to release. We conducted laboratory-based behavioural trials testing exploration, risk-taking and response to novelty using field-caught toads from the wet and dry sides of two Hawai'ian islands (Oahu and Hawai'i). Toads from the dry side of Oahu had a higher propensity to take risks than did toads from the dry side of Hawai'i. Toads from Oahu were also more exploratory than were conspecifics from the island of Hawai'i. However, toads from wet versus dry climates were similar in all behaviours that we scored, suggesting that founder effects, genetic drift, or developmentally plastic responses to ecological factors other than climate may have driven behavioural ergence between islands.
Pheromones can cull an invasive amphibian without releasing survivors from intraspecific competition
Publisher: Wiley
Date: 12-2019
DOI: 10.1002/ECS2.2969
When legislation to protect wildlife becomes a problem
Publisher: Springer Science and Business Media LLC
Date: 14-03-2023
Sex‐ And tissue‐specific differences in telomere length in a reptile
Publisher: Wiley
Date: 22-05-2019
DOI: 10.1002/ECE3.5164
The Effects of Conspecific Alarm Cues on Larval Cane Toads (Rhinella marina)
Publisher: Springer Science and Business Media LLC
Date: 10-2019
DOI: 10.1007/S10886-019-01111-2
Abstract: Many aquatic organisms detect and avoid damage-released cues from conspecifics, but the chemical basis of such responses, and the effects of prolonged exposure to such cues, remain poorly understood. Injured tadpoles of the cane toad (Rhinella marina) produce chemical cues that induce avoidance by conspecific tadpoles and chronic exposure to those cues decreases rates of tadpole survival and growth, and reduces body size at metamorphosis. Such effects suggest that we might be able to use the cane toads' alarm cue for biocontrol of invasive populations in Australia. In the present study, we examined behavioral and ecological effects of compounds that are present in cane toad tadpoles and thus, might trigger avoidance of crushed conspecifics. Four chemicals (L-Arg, L-Leu-L-Leu-OH, L-Leu-L-Ile-OH and suberic acid) induced behavioral avoidance in toad tadpoles at some (but not all) dosage levels, so we then exposed toad larvae to these chemicals over the entire period of larval development. Larval survival and size at metamorphosis were decreased by chronic exposure to crushed conspecifics (consistent with earlier studies), but not by exposure to any of the four chemicals. Indeed, L-Arg increased body size at metamorphosis. We conclude that the behavioral response to crushed conspecifics by cane toad tadpoles can be elicited by a variety of chemical cues, but that consistent exposure to these in idual chemical cues does not affect tadpole viability or developmental trajectory. The optimal behavioral tactic of a tadpole may be to flee if it encounters even a single chemical cue likely to have come from an injured conspecific (indicative of predation risk), whereas the continuing presence of that single chemical (but no others) provides a less reliable signal of predation risk. Our data are consistent with results from studies on fish, that suggest a role for multiple chemicals in initiating alarm responses to damage-released cues.
The behavioural consequences of sex reversal in dragons
Publisher: The Royal Society
Date: 15-06-2016
Abstract: Sex differences in morphology, physiology, and behaviour are caused by sex-linked genes, as well as by circulating sex-steroid levels. Thus, a shift from genotypic to environmental sex determination may create an organism that exhibits a mixture of male-like and female-like traits. We studied a lizard species (Central Bearded Dragon, Pogona vitticeps ), in which the high-temperature incubation of eggs transforms genetically male in iduals into functional females. Although they are reproductively female, sex-reversed dragons (in iduals with ZZ genotype reversed to female phenotype) resemble genetic males rather than females in morphology (relative tail length), general behaviour (boldness and activity level), and thermoregulatory tactics. Indeed, sex-reversed ‘females’ are more male-like in some behavioural traits than are genetic males. This novel phenotype may impose strong selection on the frequency of sex reversal within natural populations, facilitating rapid shifts in sex-determining systems. A single period of high incubation temperatures (generating thermally induced sex reversal) can produce functionally female in iduals with male-like (or novel) traits that enhance in idual fitness, allowing the new temperature-dependent sex-determining system to rapidly replace the previous genetically based one.
Is the behavioural divergence between range-core and range-edge populations of cane toads (Rhinella marina) due to evolutionary change or developmental plasticity?
Publisher: The Royal Society
Date: 10-2017
DOI: 10.1098/RSOS.170789
Abstract: In iduals at the leading edge of expanding biological invasions often show distinctive phenotypic traits, in ways that enhance their ability to disperse rapidly and to function effectively in novel environments. Cane toads ( Rhinella marina ) at the invasion front in Australia exhibit shifts in morphology, physiology and behaviour (directionality of dispersal, boldness, risk-taking). We took a common-garden approach, raising toads from range-core and range-edge populations in captivity, to see if the behavioural ergences observed in wild-caught toads are also evident in common-garden offspring. Captive-raised toads from the invasion vanguard population were more exploratory and bolder (more prone to ‘risky’ behaviours) than toads from the range core, which suggests that these are evolved, genetic traits. Our study highlights the importance of behaviour as being potentially adaptive in invasive populations and adds these behavioural traits to the increasing list of phenotypic traits that have evolved rapidly during the toads' 80-year spread through tropical Australia.
Within‐population variation in dietary traits: implications for vulnerability and impact of imperiled keystone predators
Publisher: Wiley
Date: 10-2020
DOI: 10.1002/ECS2.3136
Spinal arthritis in invasive cane toads is linked to rate of dispersal as well as to latitude
Publisher: Springer Science and Business Media LLC
Date: 27-09-2019
DOI: 10.1038/S41598-019-50314-W
Abstract: Initial research on the spread of cane toads ( Rhinella marina ) through tropical Australia reported a high incidence of spinal arthritis (spondylosis) in toads at the invasion front (where toads disperse rapidly), but not in areas colonized earlier (where toads are more sedentary). The idea that spondylosis was a cost of rapid dispersal was challenged by wider spatial s ling which linked rates of spondylosis to hot (tropical) climates rather than to dispersal rates. Here, the authors of these competing interpretations collaborate to reinterpret the data. Our reanalysis supports both previous hypotheses rates of spondylosis are higher in populations established by fast-dispersing toads, and are higher in tropical than in temperate environments they are also higher in larger toads. The functional reason for climatic effects is unclear, but might involve effects on the soil-living bacteria involved in the induction of spondylosis and/or may reflect higher movement (as opposed to dispersal) or more pronounced dry-season aggregation rates of toads in tropical conditions.
Seasonal shifts along the oviparity–viviparity continuum in a cold‐climate lizard population
Publisher: Wiley
Date: 13-11-2017
DOI: 10.1111/JEB.13202
Abstract: Squamate embryos require weeks of high temperature to complete development, with the result that cool climatic areas are dominated by viviparous taxa (in which gravid females can sun-bask to keep embryos warm) rather than oviparous taxa (which rely on warm soil to incubate their eggs). How, then, can some oviparous taxa reproduce successfully in cool climates - especially late in summer, when soil temperatures are falling? Near the northern limit of their distribution (in Sweden), sand lizards (Lacerta agilis) shift tactics seasonally, such that the eggs in late clutches complete development more quickly (when incubated at a standard temperature) than do those of early clutches. That acceleration is achieved by a reduction in egg size and by an increase in the duration of uterine retention of eggs (especially, after cool weather). Our results clarify the ability of oviparous reptiles to reproduce successfully in cool climates and suggest a novel advantage to reptilian viviparity in such conditions: by maintaining high body temperatures, viviparous females may escape the need to reduce offspring size in late-season litters.
Sex-based divergence in tidal, lunar and seasonal cycles of activity in the olive sea snake, Aipysurus laevis (Elapidae, Hydrophiinae)
Publisher: Springer Science and Business Media LLC
Date: 03-01-2023
Divergence in life-history traits among three adjoining populations of the sea snake Emydocephalus annulatus (Hydrophiinae, Elapidae)
Publisher: Springer Science and Business Media LLC
Date: 24-03-2022
DOI: 10.1038/S41598-022-09130-Y
Abstract: Life-history traits such as rates of growth, survival and reproduction can vary though time within a single population, or through space among populations, due to abiotically-driven changes in resource availability. In terrestrial reptiles, parameters such as temperature and rainfall generate variation in life-histories—but other parameters likely are more important in marine systems. We studied three populations of sea snakes ( Emydocephalus annulatus ) in adjacent bays in the IndoPacific archipelago of New Caledonia. The extreme philopatry of in idual snakes allows us to unambiguously allocate each animal to one of the three populations. Although water temperatures and rainfall do not differ over this small scale, one site experiences more intense winds, restricting opportunities for foraging. Our 18-year mark-recapture dataset ( 1,200 snakes, 2,400 captures) reveals significant ergence among populations in life-history traits. Survival rates and population densities were similar among sites, but snakes at the most wind-exposed site (Anse Vata) exhibited lower body condition, slower growth, less frequent production of litters, and smaller litters. Weather-driven variation in feeding rates thus may affect life-history traits of marine snakes as well as their terrestrial counterparts, but driven by different parameters (e.g., wind exposure rather than variation in temperatures or rainfall).
Brain transcriptome analysis reveals gene expression differences associated with dispersal behaviour between range-front and range-core populations of invasive cane toads in Australia
Publisher: Cold Spring Harbor Laboratory
Date: 28-09-2021
DOI: 10.1101/2021.09.27.462079
Abstract: Understanding the mechanisms underlying rapid adaptation of invasive species in novel environments is key to improving our ability to manage these species. Many invaders demonstrate rapid evolution of behavioural traits involved in range expansion such as locomotor activity, exploration and risk-taking. However, the molecular mechanisms that underpin these changes are poorly understood. In 86 years, invasive cane toads ( Rhinella marina ) in Australia have drastically expanded their geographic range westward from coastal Queensland to Western Australia. During their range expansion, toads have undergone extensive phenotypic changes, particularly in behaviours that enhance the toads’ dispersal ability. Common-garden experiments have shown that some changes in behavioural traits related to dispersal are heritable. However, genetic ersity is greatly reduced across the invasive range due to a strong founder effect, and the genetic basis underlying dispersal-related behavioural changes remains unknown. Here we used RNA-seq to compare the brain transcriptomes of toads from the Hawai’ian source population, as well as three distinct populations from across the Australian invasive range. We found markedly different gene expression profiles between the source population and Australian toads. By contrast, cane toads from across the Australian invasive range had very similar transcriptomic profiles. Yet, key genes with functions putatively related to dispersal behaviour showed differential expression between range-core and range-front populations. These genes could play an important role in the behavioural changes characteristic of range expansion in Australian cane toads.
The life aquatic: an association between habitat type and skin thickness in snakes
Publisher: Oxford University Press (OUP)
Date: 15-10-2019
DOI: 10.1093/BIOLINNEAN/BLZ136
Abstract: An aquatic animal faces challenges not encountered by its terrestrial counterparts, promoting adaptive responses in multiple traits. For ex le, a thicker dermis might protect snakes when they are pushed against sharp objects by water currents, and might enable a snake to shed fouling organisms attached to its skin. We thus predicted that marine snakes should have thicker skin than terrestrial species, and that smaller sea snakes should have relatively thicker skin (because absolute, not relative, thickness determines vulnerability to fouling). Measurements of 192 snakes of 44 species supported those predictions. Many (but not all) sea snakes have skins 50% thicker than those of terrestrial and hibious snake species, representing multiple independent evolutionary origins of thicker skin (in acrochordids, Laticauda sea kraits and both main clades of hydrophiine sea snakes). Marine snakes showed different allometries of skin thickness compared with their terrestrial counterparts larger snakes had thicker skin within and among species of hibious and terrestrial snakes, but larger aquatic snake species had thinner skin compared with smaller taxa. Interspecific variation in skin thickness was primarily due to increased collagen in the deep dermis, a physical barrier well suited to protecting against physical injury and to resisting penetration by epibionts.
Foraging mode affects extinction risk of snakes and lizards, but in different ways
Publisher: Wiley
Date: 29-08-2023
DOI: 10.1111/CONL.12977
Abstract: What factors render a species more vulnerable to extinction? In reptiles, foraging mode is a fundamental ecological dimension: some species actively search for immobile prey, whereas others ambush mobile prey. Foraging mode is linked to diet, morphology, movement ecology, and reproductive output, and hence plausibly might affect vulnerability to threatening processes. Our analyses of data on 1543 taxa revealed links between foraging mode and (IUCN) conservation status, but in opposite directions in the two main squamate groups. Ambush‐foraging snakes were more threatened and with declining populations than were active searchers, whereas lizards showed the reverse pattern. This ergence may be linked to differing consequences of foraging mode for feeding rates and reproductive frequency in snakes versus lizards. Our findings underscore the need for taxon‐specific conservation management, particularly in groups such as reptiles that have been neglected in global conservation prioritization.
The accelerating anuran: evolution of locomotor performance in cane toads ( Rhinella marina , Bufonidae) at an invasion front
Publisher: The Royal Society
Date: 11-11-2020
Abstract: As is common in biological invasions, the rate at which cane toads ( Rhinella marina ) have spread across tropical Australia has accelerated through time. In iduals at the invasion front travel further than range-core conspecifics and exhibit distinctive morphologies that may facilitate rapid dispersal. However, the links between these morphological changes and locomotor performance have not been clearly documented. We used raceway trials and high-speed videography to document locomotor traits (e.g. hop distances, heights, velocities, and angles of take-off and landing) of toads from range-core and invasion-front populations. Locomotor performance varied geographically, and this variation in performance was linked to morphological features that have evolved during the toads' Australian invasion. Geographical variation in morphology and locomotor ability was evident not only in wild-caught animals, but also in in iduals that had been raised under standardized conditions in captivity. Our data thus support the hypothesis that the cane toad's invasion across Australia has generated rapid evolutionary shifts in dispersal-relevant performance traits, and that these differences in performance are linked to concurrent shifts in morphological traits.
Wildfires modify the parasite loads of invasive cane toads
Publisher: The Royal Society
Date: 12-2021
Abstract: The frequency and severity of wildfires are increasing due to anthropogenic modifications to habitats and to climate. Post-fire landscapes may advantage invasive species via multiple mechanisms, including changes to host–parasite interactions. We surveyed the incidence of endoparasitic lungworms ( Rhabdias pseudosphaerocephala ) in invasive cane toads ( Rhinella marina ) in near-coastal sites of eastern Australia, a year after extensive fires in this region. Both the prevalence of infection and number of worms in infected toads increased with toad body size in unburned areas. By contrast, parasite load decreased with toad body size in burned areas. By killing moisture-dependent free-living lungworm larvae, the intense fires may have liberated adult cane toads from a parasite that can substantially reduce the viability of its host. Smaller toads, which are restricted to moist environments, did not receive this benefit from fires.
Sexual and geographical divergence in head widths of invasive cane toads, Rhinella marina (Anura: Bufonidae), is driven by both rapid evolution and plasticity
Publisher: Oxford University Press (OUP)
Date: 03-05-2018
The costs of parasite infection: Effects of removing lungworms on performance, growth and survival of free‐ranging cane toads
Publisher: Wiley
Date: 05-10-2017
Trade‐offs affect the adaptive value of plasticity: stronger cannibal‐induced defenses incur greater costs in toad larvae
Publisher: Wiley
Date: 20-11-2020
DOI: 10.1002/ECM.1426
Brain transcriptome analysis reveals gene expression differences associated with dispersal behaviour between range‐front and range‐core populations of invasive cane toads in Australia
Publisher: Wiley
Date: 28-01-2022
DOI: 10.1111/MEC.16347
Abstract: Understanding the mechanisms allowing invasive species to adapt to novel environments is a challenge in invasion biology. Many invaders demonstrate rapid evolution of behavioural traits involved in range expansion such as locomotor activity, exploration and risk‐taking. However, the molecular mechanisms that underpin these changes are poorly understood. In 86 years, invasive cane toads ( Rhinella marina ) in Australia have drastically expanded their geographic range westward from coastal Queensland to Western Australia. During their range expansion, toads have undergone extensive phenotypic changes, particularly in behaviours that enhance the toads’ dispersal ability. Common‐garden experiments have shown that some changes in behavioural traits related to dispersal are heritable. At the molecular level, it is currently unknown whether these changes in dispersal‐related behaviour are underlain by small or large differences in gene expression, nor is known the biological function of genes showing differential expression. Here, we used RNA‐seq to gain a better understanding of the molecular mechanisms underlying dispersal‐related behavioural changes. We compared the brain transcriptomes of toads from the Hawai'ian source population, as well as three distinct populations from across the Australian invasive range. We found markedly different gene expression profiles between the source population and Australian toads. By contrast, toads from across the Australian invasive range had very similar transcriptomic profiles. Yet, key genes with functions putatively related to dispersal behaviour showed differential expression between populations located at each end of the invasive range. These genes could play an important role in the behavioural changes characteristic of range expansion in Australian cane toads.
Rapidly evolved traits enable new conservation tools: perspectives from the cane toad invasion of Australia
Publisher: Oxford University Press (OUP)
Date: 04-06-2023
Abstract: Natural populations can show rapid adaptive responses to intense (human-mediated) environmental change. The potential for exploiting rapidly evolved traits for conservation management has been often discussed but rarely implemented. Capitalizing on a well-studied biological invasion, we here explore the idea that rapid phenotypic change in the invaders, their pathogens, and the native biota provide opportunities for managers to control invader abundance and buffer adverse impacts on native wildlife. Intensive studies of the invasion of tropical Australia by cane toads (Rhinella marina) have identified newly evolved vulnerabilities that we could exploit for toad control and newly evolved resilience of native wildlife that we could exploit for impact reduction. For ex le, distinctive phenotypes of toads at the expanding range edge enhance dispersal rate but reduce reproductive output, intraspecific competitive ability, and immunocompetence and the evolution of larval cannibalism creates opportunities not only for species-specific trapping of toad tadpoles, but also could be exploited (when allied to emerging CRISPR-Cas9 techniques) to intensify intraspecific conflict in invasive toads. That is, we could use the invasive species to control their own populations. This case study illustrates the potential of detailed basic research to identify novel approaches for conservation.
A biological invasion impacts ecosystem services: cane toads change the rate of scavenging and the suite of scavengers
Publisher: Wiley
Date: 05-2021
DOI: 10.1002/ECS2.3488
Abstract: By affecting the abundance of key native species, invasive taxa may disrupt ecosystem services. In Australia, large monitor lizards ( Varanus spp.) play critical roles as scavengers and apex predators. Our broadscale surveys (across two transects, 1300 and 2500 km) show that in tropical areas where the arrival of fatally toxic cane toads ( Rhinella marina ) has massively reduced the abundance of monitors ( Varanus panoptes ), rates of removal of deployed baits are more than halved, and the assemblages of scavengers are dominated by birds or mammals rather than reptiles. In contrast, populations of another monitor species in eastern Australia ( Varanus varius ) were little affected by toad arrival, as were scavenging rates and assemblages. The mechanisms responsible for those shifts, and their consequences on ecosystem services, warrant further research.
The loneliness of the long-distance toad: invasion history and social attraction in cane toads ( Rhinella marina )
Publisher: The Royal Society
Date: 11-2017
Abstract: In iduals at the leading edge of a biological invasion constantly encounter novel environments. These pioneers may benefit from increased social attraction, because low population densities reduce competition and risks of pathogen transfer, and increase benefits of information transfer. In standardized trials, cane toads ( Rhinella marina ) from invasion-front populations approached conspecifics more often, and spent more time close to them, than did conspecifics from high-density, long-colonized populations.
Mitochondrial genome analyses uncover intriguing population structure across the invasive trajectory of an iconic invader
Publisher: Cold Spring Harbor Laboratory
Date: 17-09-2023
Resource availability and sexual size dimorphism: differential effects of prey abundance on the growth rates of tropical snakes
Publisher: Wiley
Date: 24-04-2017
The evolution of targeted cannibalism and cannibal-induced defenses in invasive populations of cane toads
Publisher: Proceedings of the National Academy of Sciences
Date: 23-08-2021
Abstract: Invasive species are known for their ability to achieve high densities within their introduced range. Hence, invaders often face strong competition from members of their own species. Mechanisms for reducing intraspecific competition may therefore be favored in invasive populations, such as cannibalism, in which in iduals kill and eat intraspecific competitors. Here, we find that toad tadpoles from invasive Australian populations have evolved both a strong behavioral attraction to the vulnerable hatchling stage and an increased propensity to cannibalize these younger conspecifics. In response, these toads have also evolved multiple strategies for reducing the duration of the vulnerable period, indicating an evolutionary arms race between the cannibalistic tadpole stage and the vulnerable egg and hatchling stages in invaded habitats.
Long-distance movements of free-ranging sea snakes (Hydrophis, Elapidae)
Publisher: Springer Science and Business Media LLC
Date: 28-07-2023
Improving amphibian genomic resources: a multitissue reference transcriptome of an iconic invader
Publisher: Oxford University Press (OUP)
Date: 27-11-2017
The accelerating invasion: dispersal rates of cane toads at an invasion front compared to an already-colonized location
Publisher: Springer Science and Business Media LLC
Date: 11-04-2017
Intergenerational effects of manipulating DNA methylation in the early life of an iconic invader
Publisher: The Royal Society
Date: 19-04-2021
Abstract: In response to novel environments, invasive populations often evolve rapidly. Standing genetic variation is an important predictor of evolutionary response but epigenetic variation may also play a role. Here, we use an iconic invader, the cane toad ( Rhinella marina ), to investigate how manipulating epigenetic status affects phenotypic traits. We collected wild toads from across Australia, bred them, and experimentally manipulated DNA methylation of the subsequent two generations (G1, G2) through exposure to the DNA methylation inhibitor zebularine and/or conspecific tadpole alarm cues. Direct exposure to alarm cues (an indicator of predation risk) increased the potency of G2 tadpole chemical cues, but this was accompanied by reductions in survival. Exposure to alarm cues during G1 also increased the potency of G2 tadpole cues, indicating intergenerational plasticity in this inducible defence. In addition, the negative effects of alarm cues on tadpole viability (i.e. the costs of producing the inducible defence) were minimized in the second generation. Exposure to zebularine during G1 induced similar intergenerational effects, suggesting a role for alteration in DNA methylation. Accordingly, we identified intergenerational shifts in DNA methylation at some loci in response to alarm cue exposure. Substantial demethylation occurred within the sodium channel epithelial 1 subunit gamma gene ( SCNN1G ) in alarm cue exposed in iduals and their offspring. This gene is a key to the regulation of sodium in epithelial cells and may help to maintain the protective epidermal barrier. These data suggest that early life experiences of tadpoles induce intergenerational effects through epigenetic mechanisms, which enhance larval fitness. This article is part of the theme issue ‘How does epigenetics influence the course of evolution?’
In an arms race between host and parasite, a lungworm's ability to infect a toad is determined by host susceptibility not parasite preference
Publisher: The Royal Society
Date: 03-2022
Abstract: Evolutionary arms races can alter both parasite infectivity and host resistance, and it is difficult to separate the effects of these twin determinants of infection outcomes. We used a co-introduced, invasive host–parasite system (the lungworm Rhabdias pseudosphaerocephala and cane toads Rhinella marina ), where rapid adaptation and dispersal have led to population differences in infection resistance. We quantified behavioural responses of parasite larvae to skin-chemical cues of toads from different invasive populations, and rates at which juvenile hosts became infected following standardized exposure to lungworms. Chemical cues from toad skin altered host-seeking behaviour by parasites, similarly among populations. The number of infection attempts (parasite larvae entering the host's body) also did not differ between populations, but rates of successful infection (establishment of adult worm in host lungs) were higher for range-edge toads than for range-core conspecifics. Thus, lower resistance to parasite infection in range-edge juvenile toads appears to be due to less effective immune defences of the host rather than differential behavioural responses of the parasite. In this ongoing host–parasite arms race, changing outcomes appear to be driven by shifts in host immunocompetence.
Niche partitioning within a population of sea snakes is constrained by ambient thermal homogeneity and small prey size
Publisher: Oxford University Press (OUP)
Date: 10-01-2020
DOI: 10.1093/BIOLINNEAN/BLZ206
Abstract: In many populations of terrestrial snakes, the phenotype of an in idual (e.g. body size, sex, colour) affects its habitat use. One cause for that link is gape limitation, which can result in larger snakes eating prey that are found in different habitats. A second factor involves thermoregulatory opportunities, whereby in iduals select habitats based upon thermal conditions. These ideas predict minimal intraspecific variation in habitat use in a species that eats small prey and lives in a thermally uniform habitat, such as the sea snake Emydocephalus annulatus, which feeds on tiny fish eggs and lives in inshore coral reefs. To test that prediction, we gathered data on water depths and substrate attributes for 1475 sightings of 128 free-ranging E. annulatus in a bay near Noumea, New Caledonia. Habitat selection varied among in iduals, but with a preference for coral-dominated substrates. The body size and reproductive state of a snake affected its detectability in deep water, but overall habitat use was not linked to snake body size, colour morph, sex or pregnancy. A lack of ontogenetic shifts in habitat use allows extreme philopatry in E. annulatus, thereby reducing gene flow among populations and, potentially, delaying recolonization after local extirpation events.
Infection by the lungwormRhabdias pseudosphaerocephalaaffects the expression of immune-related microRNAs by its co-evolved host, the cane toadRhinella marina
Publisher: Cold Spring Harbor Laboratory
Date: 22-06-2023
DOI: 10.1101/2023.06.19.545515
Abstract: Parasites may suppress the immune function of an infected host using microRNAs (miRNAs) to prevent protein production. Nonetheless, little is known about the ersity of miRNAs and their mode(s) of action. In this study, we investigated the effects of infection by a parasitic lungworm ( Rhabdias pseudosphaerocephala ) on miRNA and mRNA expression of its host, the invasive cane toad ( Rhinella marina ). We compared miRNA and mRNA expression in naïve toads that had never been infected by lungworms to toads that were infected with lungworms for the first time in their lives, and to toads that were infected the second time in their lives (i.e., had two consecutive infections). In total, we identified 434 known miRNAs and 106 potential novel miRNAs. Compared to uninfected toads, infected animals upregulated five (single-infection treatment) or four (multiple-infection treatment) miRNAs. Seven of these differentially expressed miRNAs were associated with gene pathways related to the immune response, potentially reflecting immunosuppression of cane toads by their parasites. Infected hosts did not respond with substantial mRNA transcription, with only one differentially expressed gene between control and single-infection hosts. Our study suggests that miRNA-mediated interactions may play a role in mediating the interaction between the parasite and its host. Our findings clarify the role of miRNAs in host-parasite interactions, in a system in which an ongoing range expansion by the host has generated substantial ergence in host-parasite interactions.
Skin resistance to water gain and loss has changed in cane toads (Rhinella marina) during their Australian invasion
Publisher: Wiley
Date: 11-10-2020
DOI: 10.1002/ECE3.6895
Immune and environment‐driven gene expression during invasion: An eco‐immunological application of RNA‐Seq
Publisher: Wiley
Date: 09-05-2019
DOI: 10.1002/ECE3.5249
Rapid divergence of parasite infectivity and host resistance during a biological invasion
Publisher: Oxford University Press (OUP)
Date: 03-02-2021
DOI: 10.1093/BIOLINNEAN/BLAA229
Abstract: By perturbing co-evolved interactions, biological invasions provide an opportunity to study the evolution of interactions between hosts and their parasites on ecological timescales. We studied the interaction between the cane toad (Rhinella marina) and its direct-lifecycle lungworm (Rhabdias pseudosphaerocephala) that was brought from South America to Australia with the toads in 1935. Compared with infective parasite larvae from long-established (range-core) toad populations, parasite larvae from toads near the invasion front were larger, lived longer and were better able to resist exposure to toxin from the parotoid glands of toads. Experimentally, we infected the common-garden-reared progeny of toads from range-core and invasion-front populations within Australia with lungworms from both populations. Infective larvae from invasion-front (vs. range-core) populations of the parasite were more successful at entering toads (by skin penetration) and establishing infections in the lungs. Toads from invasion-front populations were less prone to infection by either type of larvae. Thus, within 84 years, parasites at an invasion front have increased infectivity, whereas hosts have increased resistance to parasite infection compared with range-core populations. Rapid evolution of traits might affect host–parasite interactions during biological invasions, generating unpredictable effects both on the invaders and on native ecosystems.
In an arms race between host and parasite, a lungworm’s ability to infect a toad is determined by host susceptibility, not parasite preference
Publisher: Cold Spring Harbor Laboratory
Date: 19-10-2021
DOI: 10.1101/2021.10.19.464902
Abstract: Evolutionary arms races can alter both parasite infectivity and host resistance, and it is difficult to separate the effects of these twin determinants of infection outcomes. Using a co-introduced, invasive host-parasite system (the lungworm Rhabdias pseudosphaerocephala and the cane toad Rhinella marina), we quantified behavioural responses of parasite larvae to skin-chemical cues of toads from different invasive populations, and rates at which hosts became infected following standardised exposure to lungworms. Chemical cues from toad skin altered host-seeking behaviour by parasites, similarly among populations. The number of infection attempts (parasite larvae entering the host’s body) also did not differ between populations, but rates of successful infection (establishment of adult worm in host lungs) was higher for range-edge toads than for range-core conspecifics. Thus, lower resistance to parasite infection in range-edge toads appears to be due to less effective immune defences of the host rather than differential behavioural responses of the parasite. In this ongoing host-parasite arms-race, changing outcomes appear to be driven by shifts in host immunocompetence.
It is lonely at the front: contrasting evolutionary trajectories in male and female invaders
Publisher: The Royal Society
Date: 12-2016
DOI: 10.1098/RSOS.160687
Abstract: Invasive species often exhibit rapid evolutionary changes, and can provide powerful insights into the selective forces shaping phenotypic traits that influence dispersal rates and/or sexual interactions. Invasions also may modify sexual dimorphism. We measured relative lengths of forelimbs and hindlimbs of more than 3000 field-caught adult cane toads ( Rhinella marina ) from 67 sites in Hawai'i and Australia (1–80 years post-colonization), along with 489 captive-bred in iduals from multiple Australian sites raised in a ‘common garden’ (to examine heritability and reduce environmental influences on morphology). As cane toads spread from east to west across Australia, the ancestral condition (long limbs, especially in males) was modified. Limb length relative to body size was first reduced (perhaps owing to natural selection on locomotor ability), but then increased again (perhaps owing to spatial sorting) in the invasion vanguard. In contrast, the sex disparity in relative limb length has progressively decreased during the toads' Australian invasion. Offspring reared in a common environment exhibited similar geographical ergences in morphology as did wild-caught animals, suggesting a genetic basis to the changes. Limb dimensions showed significant heritability (2–17%), consistent with the possibility of an evolved response. Cane toad populations thus have undergone a major shift in sexual dimorphism in relative limb lengths during their brief (81 years) spread through tropical Australia.
Antipredator tactics: a kin‐selection benefit for defensive spines in coral catfish?
Publisher: Wiley
Date: 10-11-2020
DOI: 10.1111/OIK.07838
A famous failure: Why were cane toads an ineffective biocontrol in Australia?
Publisher: Wiley
Date: 06-10-2020
DOI: 10.1111/CSP2.296
Anthropogenically modified habitats favor bigger and bolder lizards
Publisher: Wiley
Date: 31-01-2021
DOI: 10.1002/ECE3.7124
Using experimental de-worming to measure the immunological and pathological impacts of lungworm infection in cane toads
Publisher: Elsevier BV
Date: 12-2017
Divergence in host–parasite interactions during the cane toad's invasion of Australia
Publisher: Wiley
Date: 08-2022
DOI: 10.1002/ECE3.9220
Abstract: Coevolutionary host–parasite “arms races” can be disrupted by new evolutionary forces imposed by biological invasions, affecting both host and parasite densities, as well as their traits. The spread of cane toads ( Rhinella marina ) and their parasitic lungworm ( Rhabdias pseudosphaerocephala ) across tropical Australia provides an ideal opportunity to study a perturbed host–parasite system. We conducted a cross‐infection experiment using common‐garden‐reared toads and lungworms from three regions (comprising long‐established, intermediate, and recently invaded sites across tropical Australia) to quantify traits of the parasite (infectivity and virulence) and the host (resistance and tolerance). Specifically, we assessed whether patterns of host–parasite co‐adaptation were better explained by spatial distances versus time since the separation of host and parasite populations. Infection success was highest when toads from long‐established populations were exposed to lungworms from close to the invasion front and lowest when frontal toads were exposed to parasites from older populations. This suggests that both parasite infectivity and host resistance have increased over the course of invasion. In contrast, most virulence/tolerance traits have not consistently increased or decreased during invasion. Higher parasite burdens were associated with increased feeding performance in toads and faster growth in lungworms, counter‐intuitive results that suggest host manipulation by the parasite.
Chemical cues that attract cannibalistic cane toad (Rhinella marina) larvae to vulnerable embryos
Publisher: Springer Science and Business Media LLC
Date: 15-06-2021
DOI: 10.1038/S41598-021-90233-3
Abstract: Chemical cues produced by late-stage embryos of the cane toad ( Rhinella marina ) attract older conspecific larvae, which are highly cannibalistic and can consume an entire clutch. To clarify the molecular basis of this attraction response, we presented captive tadpoles with components present in toad eggs. As previously reported, attractivity arises from the distinctive toxins (bufadienolides) produced by cane toads, with some toxins (e.g., bufagenins) much stronger attractants than others (e.g., bufotoxins). Extracts of frozen toad parotoid glands (rich in bufagenins) were more attractive than were fresh MeOH extracts of the parotoid secretion (rich in bufotoxins), and purified marinobufagin was more effective than marinobufotoxin. Cardenolide aglycones (e.g., digitoxigenin) were active attractors, whereas C-3 glycosides (e.g., digoxin, oubain) were far less effective. A structure–activity relationship study revealed that tadpole attractant potency strongly correlated with Na + /K + ATPase inhibitory activity, suggesting that tadpoles monitor and rapidly react to perturbations to Na + /K + ATPase activity.
Behavioural responses of an Australian colubrid snake (Dendrelaphis punctulatus) to a novel toxic prey item (the Cane Toad Rhinella marina)
Publisher: Springer Science and Business Media LLC
Date: 26-03-2018
Thyroid hormone modulates offspring sex ratio in a turtle with temperature-dependent sex determination
Publisher: The Royal Society
Date: 26-10-2016
Abstract: The adaptive significance of temperature-dependent sex determination (TSD) has attracted a great deal of research, but the underlying mechanisms by which temperature determines the sex of a developing embryo remain poorly understood. Here, we manipulated the level of a thyroid hormone (TH), triiodothyronine (T 3 ), during embryonic development (by adding excess T 3 to the eggs of the red-eared slider turtle Trachemys scripta , a reptile with TSD), to test two competing hypotheses on the proximate basis for TSD: the developmental rate hypothesis versus the hormone hypothesis . Exogenous TH accelerated embryonic heart rate (and hence metabolic rate), developmental rate, and rates of early post-hatching growth. More importantly, hyperthyroid conditions depressed expression of Cyp19a1 (the gene encoding for aromatase) and levels of oestradiol, and induced more male offspring. This result is contrary to the direction of sex-ratio shift predicted by the developmental rate hypothesis , but consistent with that predicted by the hormone hypothesis . Our results suggest an important role for THs in regulating sex steroid hormones, and therefore, in affecting gonadal sex differentiation in TSD reptiles. Our study has implications for the conservation of TSD reptiles in the context of global change because environmental contaminants may disrupt the activity of THs, and thereby affect offspring sex in TSD reptiles.
Sex-based differences in the use of post-fire habitats by invasive cane toads (Rhinella marina)
Publisher: Springer Science and Business Media LLC
Date: 23-06-2022
DOI: 10.1038/S41598-022-14697-7
Abstract: Wildfires can modify habitat attributes, and those changes may differentially affect males versus females within a species if there is pre-existing niche ergence between the sexes. We used radio-tracking and dissections to study invasive cane toads ( Rhinella marina ), and performed transect counts on native frogs and cane toads 12 months after extensive fires in forests of eastern Australia. Both toads and native frogs were encountered more frequently in burned sites than in unburned sites. Most microhabitat features were similar between burned versus unburned areas, but fire had differential impacts on the ecology of male versus female toads. In burned areas females were less numerous but were larger, in better body condition, and had consumed more prey (especially, coleopterans and myriapods). The impact of fire on attributes of retreat-sites (e.g., temperature, density of vegetation cover) also differed between the sexes. More generally, intraspecific ergence in ecological traits within a species (as a function of body size as well as sex) may translate into substantial ergences in the impacts of habitat change.
Is developmental plasticity triggered by DNA methylation changes in the invasive cane toad (Rhinella marina)?
Publisher: Cold Spring Harbor Laboratory
Date: 26-10-2023
An invasion in slow motion: the spread of invasive cane toads (Rhinella marina) into cooler climates in southern Australia
Publisher: Springer Science and Business Media LLC
Date: 09-07-2021
The gut bacteria of an invasive amphibian respond to the dual challenges of range-expansion and parasite attack
Publisher: Cold Spring Harbor Laboratory
Date: 17-11-2020
DOI: 10.1101/2020.11.16.385690
Abstract: Gut bacterial communities influence, and are influenced by, the behaviour and ecology of their hosts. Those interactions have been studied primarily in humans and model organisms, but we need field research to understand the relationship between an organism’s gut bacteria and its ecological challenges, such as those imposed by rapid range expansion (as in invasive species) and the presence of host-manipulating parasites. Cane toads ( Rhinella marina ) provide an excellent model system in this respect, because the species’ ongoing colonization of Australia has enforced major changes in phenotypic traits (including behaviour), and lungworm parasites ( Rhabdias pseudosphaerocephala ) modify host gut function in ways that enhance the viability of lungworm larvae. We collected female toads from across the species’ invasive range and studied their morphology, behaviour, parasite infection status and gut bacterial community. Range-core versus range-edge toads differed in morphology, behaviour, gut bacterial composition and predicted gut bacterial function but did not differ in the occurrence of parasite infection nor in the intensity of infection. Toads infected with lungworms differed from uninfected conspecifics in gut bacterial composition and ersity. Our study demonstrates strong associations between gut bacterial community and host ecology and behaviour.
Geographic variation in bacterial assemblages on cane toad skin is influenced more by local environments than by evolved changes in host traits
Publisher: The Company of Biologists
Date: 06-02-2023
DOI: 10.1242/BIO.059641
Abstract: Bacterial assemblages on hibian skin may play an important role in protecting hosts against infection. In hosts that occur over a range of environments, geographic variation in composition of bacterial assemblages might be due to direct effects of local factors and/or to evolved characteristics of the host. Invasive cane toads (Rhinella marina) are an ideal candidate to evaluate environmental and genetic mechanisms, because toads have evolved major shifts in physiology, morphology, and behavior during their brief history in Australia. We used s les from free-ranging toads to quantify site-level differences in bacterial assemblages and a common-garden experiment to see if those differences disappeared when toads were raised under standardised conditions at one site. The large differences in bacterial communities on toads from different regions were not seen in offspring raised in a common environment. Relaxing bacterial clustering to operational taxonomic units in place of licon sequence variants likewise revealed high similarity among bacterial assemblages on toads in the common-garden study, and with free-ranging toads captured nearby. Thus, the marked geographic ergence in bacterial assemblages on wild-caught cane toads across their Australian invasion appears to result primarily from local environmental effects rather than evolved shifts in the host.
Invasion of cane toads (Rhinella marina) affects the problem-solving performance of vulnerable predators (monitor lizards, Varanus varius)
Publisher: Springer Science and Business Media LLC
Date: 27-01-2021
Urbanization and translocation disrupt the relationship between host density and parasite abundance
Publisher: Wiley
Date: 20-02-2020
Abstract: The species interactions that structure natural communities are increasingly disrupted by radical habitat change resulting from the widespread processes of urbanization and species translocations. Although many species are disadvantaged by these changes, others thrive in these new environments, achieving densities that exceed those in natural habitats. Often the same species that benefit from urbanization are successful invaders in introduced habitats, suggesting that similar processes promote these species in both environments. Both processes may especially benefit certain species by modifying their interactions with harmful parasites ('enemy release'). To detect such modifications, we first need to identify the mechanisms underlying host-parasite associations in natural populations, then test whether they are disrupted in cities and introduced habitats. We studied the interaction between the cane toad Rhinella marina, a globally invasive species native to South America, and its Amblyomma ticks. Our field study of 642 cane toads across 46 sites within their native range in French Guiana revealed that 56% of toads carried ticks, and that toads with ticks were in poor body condition relative to uninfected conspecifics. Across natural and disturbed habitats tick prevalence and abundance increased with toad density, but this association was disrupted in the urban environment, where tick abundance remained low even where toad densities were high, and prevalence decreased with density. Reductions in the abundance of ticks in urban habitats may be attributable to pesticides (which are sprayed for mosquito control but are also lethal to ticks), and our literature review shows that tick abundance is generally lower in cane toads from urban habitats across South America. In the invasive range, ticks were either absent (in 1,960 toads from Puerto Rico, Hawai'i, Japan and Australia) or less abundant (in Florida and the Caribbean literature review). The positive relationship between host density and parasite abundance is thought to be a key mechanism through which parasites regulate host populations anthropogenic processes that disrupt this relationship may allow populations in urban and introduced habitats to persist at densities that would otherwise lead to severe impacts from parasites.
Life history traits of the sea snake Emydocephalus annulatus, based on a 17-yr study
Publisher: Springer Science and Business Media LLC
Date: 08-07-2020
Maternal body size influences offspring immune configuration in an oviparous snake
Publisher: The Royal Society
Date: 03-2016
DOI: 10.1098/RSOS.160041
Abstract: Like most ectothermic vertebrates, keelback snakes ( Tropidonophis mairii ) do not exhibit parental care. Thus, offspring must possess an immune system capable of dealing with challenges such as pathogens, without assistance from an attendant parent. We know very little about immune system characteristics of neonatal reptiles, including the magnitude of heritability and other maternal influences. To identify sources of variation in circulating white blood cell (WBC) concentrations and differentials, we examined blood smears from 246 hatchling snakes and their field-caught mothers. WBC concentrations were lower in hatchlings than in adults, and hatchlings had more basophils and fewer azurophils than adults. A hatchling keelback's WBC differential was also influenced by its sex and body size. Although hatchling WBC measures exhibited negligible heritability, they were strongly influenced by maternal body size and parasite infection (but not by maternal body condition, relative clutch mass or time in captivity). Larger mothers produced offspring with more azurophils and fewer lymphocytes. The mechanisms and consequences of WBC variation are currently unknown, but if these maternal effects enhance offspring fitness, the impact of maternal body size on reproductive success may be greater than expected simply from allometric increases in the numbers and sizes of progeny.
Do changes in body mass alter white blood cell profiles and immune function in Australian cane toads ( Rhinella marina )?
Publisher: The Royal Society
Date: 12-06-2023
Abstract: Variation in food resources can result in dramatic fluctuations in the body condition of animals dependent on those resources. Decreases in body mass can disrupt patterns of energy allocation and impose stress, thereby altering immune function. In this study, we investigated links between changes in body mass of captive cane toads ( Rhinella marina ), their circulating white blood cell populations, and their performance in immune assays. Captive toads that lost weight over a three-month period had increased levels of monocytes and heterophils and reduced levels of eosinophils. Basophil and lymphocyte levels were unrelated to changes in mass. Because in iduals that lost mass had higher heterophil levels but stable lymphocyte levels, the ratio of these cell types was also higher, partially consistent with a stress response. Phagocytic ability of whole blood was higher in toads that lost mass, owing to increased circulating levels of phagocytic cells. Other measures of immune performance were unrelated to mass change. These results highlight the challenges faced by invasive species as they expand their range into novel environments which may impose substantial seasonal changes in food availability that were not present in the native range. In iduals facing energy restrictions may shift their immune function towards more economical and general avenues of combating pathogens. This article is part of the theme issue ‘Amphibian immunity: stress, disease and ecoimmunology’.
Mistaken identity may explain why male sea snakes (Aipysurus laevis, Elapidae, Hydrophiinae) “attack” scuba divers
Publisher: Springer Science and Business Media LLC
Date: 19-08-2021
DOI: 10.1038/S41598-021-94728-X
Abstract: Scuba- ers on tropical coral-reefs often report unprovoked “attacks” by highly venomous Olive sea snakes ( Aipysurus laevis ). Snakes swim directly towards ers, sometimes wrapping coils around the er’s limbs and biting. Based on a focal animal observation study of free-ranging Olive sea snakes in the southern Great Barrier Reef, we suggest that these “attacks” are misdirected courtship responses. Approaches to ers were most common during the breeding season (winter) and were by males rather than by female snakes. Males also made repeated approaches, spent more time with the er, and exhibited behaviours (such as coiling around a limb) also seen during courtship. Agitated rapid approaches by males, easily interpreted as “attacks”, often occurred after a courting male lost contact with a female he was pursuing, after interactions between rival males, or when a er tried to flee from a male. These patterns suggest that “attacks” by sea snakes on humans result from mistaken identity during sexual interactions. Rapid approaches by females occurred when they were being chased by males. Divers that flee from snakes may inadvertently mimic the responses of female snakes to courtship, encouraging males to give chase. To prevent escalation of encounters, ers should keep still and avoid retaliation.
Survival of the feces: Does a nematode lungworm adaptively manipulate the behavior of its cane toad host?
Publisher: Wiley
Date: 15-04-2018
DOI: 10.1002/ECE3.3870
The thermal dependency of locomotor performance evolves rapidly within an invasive species
Publisher: Wiley
Date: 02-04-2018
DOI: 10.1002/ECE3.3996
Apparent lack of spill-over of parasites from an invasive anuran: PCR detects Entamoeba in cane toads (Rhinella marina) but not in sympatric Australian native frogs
Publisher: Elsevier BV
Date: 08-2020
Extreme plasticity in reproductive biology of an oviparous lizard
Publisher: Wiley
Date: 11-06-2018
DOI: 10.1002/ECE3.4247
Immune configuration in hatchling snakes is affected by incubation moisture, and is linked to subsequent growth and survival in the field
Publisher: Wiley
Date: 26-03-2018
DOI: 10.1002/JEZ.2154
Abstract: We incubated the eggs of field-caught keelback snakes (Tropidonophis mairii) on wet versus dry substrates to explore impacts of incubation conditions on white blood cell (WBC) concentrations and differential WBC counts of hatchlings. In a second, independent study young snakes were released into the field, allowing us to explore fitness correlates of WBC profiles. Dry incubation reduced embryonic survival and hatchling body size, thus decoupling egg size from hatchling size. Incubation conditions also altered WBC profiles. Lymphocyte and azurophil counts were related to hatchling body size but not to initial egg mass, whereas heterophil counts were related to both of these traits. The egg-size effect on heterophil counts may reflect a maternal effect on offspring immune configuration. The ratio of heterophils to lymphocytes (an index of stress) was higher in hatchlings from eggs incubated on dry substrates. Snakes with higher counts of lymphocytes at hatching were more likely to be recaptured as adults (H:L an index of survival), whereas snakes with higher basophil counts exhibited more rapid growth. In summary, our experiments show that incubation moisture levels influence the immune configuration of hatchling snakes, and that variation among in iduals in WBC counts at hatching is a significant predictor of an in idual's fitness after it is released into the wild. The demonstrated link between incubation conditions and offspring fitness is likely to impose strong selection on maternal nest-site choice.
Locomotor performance of cane toads differs between native-range and invasive populations
Publisher: The Royal Society
Date: 07-2017
DOI: 10.1098/RSOS.170517
Abstract: Invasive species provide a robust opportunity to evaluate how animals deal with novel environmental challenges. Shifts in locomotor performance—and thus the ability to disperse—(and especially, the degree to which it is constrained by thermal and hydric extremes) are of special importance, because they might affect the rate that an invader can spread. We studied cane toads ( Rhinella marina ) across a broad geographical range: two populations within the species' native range in Brazil, two invasive populations on the island of Hawai'i and eight invasive populations encompassing the eastern, western and southern limits of the toad invasion in Australia. A toad's locomotor performance on a circular raceway was strongly affected by both its temperature and its hydration state, but the nature and magnitude of those constraints differed across populations. In their native range, cane toads exhibited relatively low performance (even under optimal test conditions) and a rapid decrease in performance at lower temperatures and hydration levels. At the other extreme, performance was high in toads from southern Australia, and virtually unaffected by desiccation. Hawai'ian toads broadly resembled their Brazilian conspecifics, plausibly reflecting similar climatic conditions. The invasion of Australia has been accompanied by a dramatic enhancement in the toads' locomotor abilities, and (in some populations) by an ability to maintain locomotor performance even when the animal is cold and/or dehydrated. The geographical ergences in performance among cane toad populations graphically attest to the adaptability of invasive species in the face of novel abiotic challenges.
A biological invasion reduces rates of cannibalism by Japanese toad tadpoles
Publisher: Springer Science and Business Media LLC
Date: 13-06-2023
DOI: 10.1038/S41598-023-36743-8
Abstract: Biological invasions can favour rapid changes in intraspecific competitive mechanisms such as cannibalism by imposing novel evolutionary pressures. For ex le, cane toad ( Rhinella marina ) tadpoles are highly cannibalistic on eggs and hatchlings in their invasive range in Australia, but not in their native range in South America. Whether such changes in cannibalism occur in invasive populations of other hibian species is unknown. To explore this question, we collected wild-laid egg clutches of Japanese common toads ( Bufo japonicus ) from native and invasive populations in Japan, and conducted laboratory experiments to examine cannibalism responses. Contrary to the Australian system, we found that invasion has been accompanied by reduced cannibalistic tendency of B. japonicus tadpoles. This reduction has occurred despite invasive-range B. japonicus eggs/hatchlings being more vulnerable than native-range B. japonicus eggs/hatchlings to cannibalism by native-range conspecific tadpoles, and to predation by native-range frog tadpoles. Our findings thus support the idea that biological invasions can generate rapid changes in rates of cannibalism, but also show that decreases as well as increases can occur. Future work could investigate the proximate cues and selective forces responsible for this rapid decrease in rates of cannibalism by tadpoles in an invasive B. japonicus population.
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.
Laid-back invaders: Cane toads (Rhinella marina) down-regulate their stress responses as they colonize a harsh climate
Publisher: Elsevier BV
Date: 12-2020
Peaceful coexistence between people and deadly wildlife: Why are recreational users of the ocean so rarely bitten by sea snakes?
Publisher: Wiley
Date: 11-05-2011
DOI: 10.1002/PAN3.10190
Sex and weaponry: The distribution of toxin‐storage glands on the bodies of male and female cane toads (Rhinella marina)
Publisher: Wiley
Date: 22-09-2017
DOI: 10.1002/ECE3.2914
Frequency-dependent Batesian mimicry maintains colour polymorphism in a sea snake population
Publisher: Springer Science and Business Media LLC
Date: 18-03-2022
DOI: 10.1038/S41598-022-08639-6
Abstract: Evolutionary theory suggests that polymorphic traits can be maintained within a single population only under specific conditions, such as negative frequency-dependent selection or heterozygote advantage. Non-venomous turtle-headed sea snakes ( Emydocephalus annulatus ) living in shallow bays near Noumea in New Caledonia exhibit three colour morphs: black, black-and-white banded, and an intermediate (grey-banded) morph that darkens with age. We recorded morph frequencies during 18 consecutive years of surveys, and found that the numbers of recruits (neonates plus immigrants) belonging to each morph increased in years when that morph was unusually rare in the population, and decreased when that morph was unusually common. Thus, morph frequencies are maintained by negative frequency-dependent selection. We interpret the situation as Batesian mimicry of highly venomous sea snakes ( Aipysurus, Hydrophis, Laticauda ) that occur in the same bays, and range in colour from black-and-white banded to grey-banded. Consistent with the idea that mimicry may protect snakes from attack by large fish and sea eagles, behavioural studies have shown that smaller fish species in these bays flee from banded snakes but attack black in iduals. As predicted by theory, mimetic (banded) morphs are less common than the cryptically-coloured melanic morph.
Field trials of chemical suppression of embryonic cane toads (Rhinella marina) by older conspecifics
Publisher: Wiley
Date: 31-08-2020
DOI: 10.1002/ECE3.6678
Thin-skinned invaders: geographic variation in the structure of the skin among populations of cane toads (Rhinella marina)
Publisher: Oxford University Press (OUP)
Date: 15-09-2020
DOI: 10.1093/BIOLINNEAN/BLAA128
Abstract: The structure of the skin may evolve rapidly during a biological invasion, for two reasons. First, novel abiotic challenges such as hydric conditions may modify selection of traits (such as skin thickness) that determine rates of evaporative water loss. Second, invaders might benefit from enhanced rates of dispersal, with locomotion possibly facilitated by thinner (and hence more flexible) skin. We quantified thickness of layers of the skin in cane toads (Rhinella marina) from the native range (Brazil), a stepping-stone population (Hawaii), and the invaded range in Australia. Overall, the skin is thinner in cane toads in Australia than in the native range, consistent with selection on mobility. However, layers that regulate water exchange (epidermal stratum corneum and dermal ground substance layer) are thicker in Australia, retarding water loss in hot dry conditions. Within Australia, epidermal thickness increased as the toads colonized more arid regions, but then decreased in the arid Kimberley region. That curvilinearity might reflect spatial sorting, whereby mobile (thin-skinned) in iduals dominate the invasion front or the toads’ restriction to moist sites in this arid landscape may reduce the importance of water-conservation. Further work is needed to clarify the roles of adaptation versus phenotypic plasticity in generating the strong geographic variation in skin structure among populations of cane toads.
Taking the bait: Developing a bait delivery system to target free‐ranging crocodiles and varanid lizards with a novel conservation strategy
Publisher: Wiley
Date: 06-2022
DOI: 10.1002/ECE3.8933
Abstract: In tropical Australia, conditioned taste aversion (CTA) can buffer vulnerable native predators from the invasion of a toxic prey species (cane toads, Rhinella marina ). Thus, we need to develop methods to deploy aversion‐inducing baits in the field, in ways that maximize uptake by vulnerable species (but not other taxa). We constructed and field‐tested baiting devices, in situ with wild animals. Apparatus were set next to waterbodies and baited concurrently at multiple locations (over water, water's edge, and on the bank). Baits were checked and replaced twice daily during the trial remote cameras recorded visitation by native predators. Bait longevity was compared at sun‐exposed and shaded locations over 12 h. The strength required to remove baits from apparatus was measured in varanids and crocodiles. The device promoted high rates of bait uptake by freshwater crocodiles (47% baits consumed), varanid lizards (19% baits consumed), and non‐target taxa (34% baits consumed). Targeting specific predators can be achieved by manipulating bait location and time of deployment, as well as the force required to dislodge the bait. Crocodiles were best targeted with over‐water baits, whereas varanid lizards preferred baits located at the edges of waterbodies. When testing bait longevity in ambient conditions, during the daytime baits desiccated fully within 12 h, and faster in the sun than in the shade. Based on studies using captive animals, the “pulling force” strength of reptilian predators scaled with body size and was greater in crocodiles than in varanid lizards. We present the first conservation baiting protocol designed specifically for reptiles. Our results demonstrate the feasibility of widespread and taxon‐specific deployment of aversion‐inducing baits to buffer the impacts of invasive cane toads, and our methods are applicable (with modification) to other research and management programs globally.
At the invasion front, male cane toads (Rhinella marina) have smaller testes
Publisher: The Royal Society
Date: 07-2019
Abstract: As a colonizing species expands its range, in iduals at the invasion front experience different evolutionary pressures than do those at the range-core. For ex le, low densities at the edge of the range mean that males should rarely experience intense sperm competition from rivals and investment into reproduction may trade-off with adaptations for more rapid dispersal. Both of these processes are predicted to favour a reduction in testis size at the invasion front. To explore effects of invasion stage in Australian cane toads ( Rhinella marina ), we collected and dissected 214 adult males from three regions: one in the species' range-core (northeastern Australia), and two from invasion fronts (one in northwestern Australia and one in southeastern Australia). Despite the brief duration of separation between toads in these areas (approx. 85 years), testis masses averaged greater than 30% higher (as a proportion of body mass) in range-core males than in conspecifics s led from either vanguard of the invasion. Previous work has documented low reproductive frequencies in female cane toads at the invasion front also, consistent with the hypothesis that evolutionary and ecological pressures unleashed by an invasion can favour relatively low resource allocation to reproduction in both sexes.
Choosy cannibals: Targeted consumption of conspecific hatchlings by larval cane toads is triggered by species‐specific defensive toxins
Publisher: Wiley
Date: 03-2022
DOI: 10.1002/ECE3.8655
Abstract: In many species, cannibalism is uncommon and involves nonselective consumption of conspecifics as well as heterospecifics. However, within their invasive Australian range, cane toad larvae ( Rhinella marina ) specifically target and voraciously consume the eggs and hatchlings of conspecifics, often extirpating entire clutches. In contrast, toad larvae rarely consume the eggs and hatchlings of native frogs. Here, we use laboratory studies to demonstrate that this selective consumption is triggered by species‐specific chemical cues: maternally‐invested bufadienolide toxins that otherwise defend cane toad eggs and hatchlings against predators. We find that these cues stimulate feeding behaviors in toad tadpoles, such that the addition of bufadienolide toxins to the water column increases predation on eggs, not only of conspecifics, but also of native anuran species that are otherwise usually ignored. In contrast, we find that cannibalism rates on conspecific hatchlings are high and unaffected by the addition of bufadienolide cues. The maternally‐invested toxins present in conspecific eggs may therefore be more easily detected post‐hatching, at which point tadpole feeding behaviors are induced whether or not additional toxin cues are present. As bufadienolide cues have previously been found to attract toad tadpoles to vulnerable hatchlings, our present findings demonstrate that the same toxin cues that attract cannibalistic tadpoles also induce them to feed, thereby facilitating cannibalism through multiple behavioral effects. Because native fauna do not produce bufadienolide toxins, the species specificity of these chemical cues in the Australian landscape may have facilitated the evolution of targeted (species‐specific) cannibalism in invasive cane toad populations. Thus, these bufadienolide toxins confer cost (increased vulnerability to cannibalism in early life‐stages) as well as benefit (reduced vulnerability to predation by other taxa).
Is the enhanced dispersal rate seen at invasion fronts a behaviourally plastic response to encountering novel ecological conditions?
Publisher: The Royal Society
Date: 09-2016
Abstract: As a population expands into novel areas (as occurs in biological invasions), the range edge becomes dominated by rapidly dispersing in iduals—thereby accelerating the rate of population spread. That acceleration has been attributed to evolutionary processes (natural selection and spatial sorting), to which we add a third complementary process: behavioural plasticity. Encountering environmental novelty may directly elicit an increased rate of dispersal. When we reciprocally translocated cane toads ( Rhinella marina ) among study sites in southern Australia, the transported animals massively increased dispersal rates relative to residents (to an extent similar to the evolved increase between range-core versus invasion-front toad populations in Australia). The responses of these translocated toads show that even range-core toads are capable of the long-distance dispersal rates of invasion-front conspecifics and suggest that rapid dispersal (rather than evolving de novo ) has simply been expanded from facultative to constitutive expression.
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.
First in family Rhabdiasidae: the reference-guided genome assembly of an invasive parasite, the cane toad lungworm (Rhabdias pseudosphaerocephala)
Publisher: Cold Spring Harbor Laboratory
Date: 28-02-2023
DOI: 10.1101/2023.02.28.530339
Abstract: Rhabdias pseudosphaerocephala is a well-studied invasive nematode parasite of hibians. However, there are several outstanding questions about R. pseudosphaerocephala that are best answered using genomic data. This species differs phenotypically across its invasive range. These differences are challenging to interpret because this species is part of a complex that is erse and cryptic in its home-range, and we do not know how many species from this complex originally colonised Australia. For this reason, it is unknown whether the phenotypic differences across the introduced range are due to intraspecific differentiation between populations or due to the presence of multiple species. In addition, there is little consensus in the placement of Rhabdiasidae family within the phylum Nematoda, making it difficult to perform comparative analyses with other nematodes. Within this paper, we assemble a reference genome for R. pseudosphaerocephala , the first assembly of any Rhabdiasidae species. We then use resequencing data to address outstanding questions about this species. Specifically, we combine population genetic and phylogenetic analyses to determine that there is likely only a single R. pseudosphaerocephala lineage within Australia, and identify that the invasive range population is closely related to home rage isolates that infect similar host species. We present compelling evidence for a genetic bottleneck following introduction to Australia and genetic differentiation occurring between invasive range populations. We then use genome-scale phylogenomic analysis to place the Rhabdiasidae family in the suborder Rhabditina. Ultimately, this paper brings the study of Rhabdiasidae into the genomic era, and sheds light on its ancient and modern evolutionary history.
Related Organisations
No related organisations have been discovered for Richard Shine.
Related Funding Activities
Discovery Projects - Grant ID: DP0343673
Start Date: 2003
End Date: 12-2007
Amount: $925,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP150100501
Start Date: 2016
End Date: 12-2018
Amount: $704,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP220100164
Start Date: 2023
End Date: 12-2025
Amount: $621,543.00
Funder: Australian Research Council
View Funded ActivityFederation Fellowships - Grant ID: FF0561365
Start Date: 01-2006
End Date: 06-2011
Amount: $1,551,625.00
Funder: Australian Research Council
View Funded ActivityLinkage - International - Grant ID: LX0346809
Start Date: 02-2004
End Date: 01-2007
Amount: $42,000.00
Funder: Australian Research Council
View Funded ActivityAustralian Laureate Fellowships - Grant ID: FL120100074
Start Date: 05-2013
End Date: 05-2018
Amount: $2,175,454.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP0776647
Start Date: 07-2008
End Date: 02-2013
Amount: $773,060.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP110200473
Start Date: 02-2012
End Date: 12-2016
Amount: $530,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP170100198
Start Date: 2018
End Date: 07-2022
Amount: $725,505.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP170100013
Start Date: 07-2017
End Date: 12-2023
Amount: $860,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP0775167
Start Date: 07-2007
End Date: 07-2010
Amount: $503,683.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP160102991
Start Date: 2016
End Date: 12-2021
Amount: $385,700.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0770296
Start Date: 07-2007
End Date: 10-2011
Amount: $879,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP190100507
Start Date: 06-2019
End Date: 06-2024
Amount: $1,110,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP130101805
Start Date: 01-2013
End Date: 06-2016
Amount: $450,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0208246
Start Date: 2002
End Date: 12-2006
Amount: $932,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE0561251
Start Date: 03-2005
End Date: 04-2006
Amount: $150,887.00
Funder: Australian Research Council
View Funded ActivityResearch Networks - Grant ID: RN0457921
Start Date: 10-2004
End Date: 10-2009
Amount: $1,500,000.00
Funder: Australian Research Council
View Funded ActivitySpecial Research Initiatives - Grant ID: SR0354791
Start Date: 2004
End Date: 12-2004
Amount: $40,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Infrastructure, Equipment And Facilities - Grant ID: LE0883055
Start Date: 02-2008
End Date: 10-2008
Amount: $170,000.00
Funder: Australian Research Council
View Funded ActivityLinkage Projects - Grant ID: LP100100740
Start Date: 06-2010
End Date: 06-2015
Amount: $625,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0984771
Start Date: 03-2009
End Date: 03-2014
Amount: $900,000.00
Funder: Australian Research Council
View Funded Activity