ORCID Profile
0000-0002-3010-6768
Current Organisation
James Cook University
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Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-07-2006
Publisher: CRC Press
Date: 02-06-2010
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.DCI.2017.08.018
Abstract: Temperature variability, and in particular temperature decreases, can increase susceptibility of hibians to infections by the fungus Batrachochytrium dendrobatidis (Bd). However, the effects of temperature shifts on the immune systems of Bd-infected hibians are unresolved. We acclimated frogs to 16 °C and 26 °C (baseline), simultaneously transferred them to an intermediate temperature (21 °C) and inoculated them with Bd (treatment), and tracked their infection levels and white blood cell profiles over six weeks. Average weekly infection loads were consistently higher in 26°C-history frogs, a group that experienced a 5 °C temperature decrease, than in 16°C-history frogs, a group that experienced a 5 °C temperature increase, but this pattern only approached statistical significance. The 16°C-acclimated frogs had high neutrophil:lymphocyte (N:L) ratios (suggestive of a hematopoietic stress response) at baseline, which were conserved post-treatment. In contrast, the 26°C-acclimated frogs had low N:L ratios at baseline which reversed to high N:L ratios post-treatment (suggestive of immune system activation). Our results suggest that infections were less physiologically taxing for the 16°C-history frogs than the 26°C-history frogs because they had already adjusted immune parameters in response to challenging conditions (cold). Our findings provide a possible mechanistic explanation for observations that hibians are more susceptible to Bd infection following temperature decreases compared to increases and underscore the consensus that increased temperature variability associated with climate change may increase the impact of infectious diseases.
Publisher: JSTOR
Date: 12-1993
DOI: 10.2307/1564826
Publisher: Public Library of Science (PLoS)
Date: 27-12-2012
Publisher: Public Library of Science (PLoS)
Date: 18-10-2011
Publisher: Wiley
Date: 06-2019
DOI: 10.1111/MEC.15108
Abstract: Recent decades have seen the emergence and spread of numerous infectious diseases, often with severe negative consequences for wildlife populations. Nevertheless, many populations survive the initial outbreaks, and even undergo recoveries. Unfortunately, the long-term effects of these outbreaks on host population genetics are poorly understood to increase this understanding, we examined the population genetics of two species of rainforest frogs (Litoria nannotis and Litoria serrata) that have largely recovered from a chytridiomycosis outbreak at two national parks in the Wet Tropics of northern Australia. At the wetter, northern park there was little evidence of decreased genetic ersity in either species, and all of the s led sites had high minor allele frequencies (mean MAF = 0.230-0.235), high heterozygosity (0.318-0.325), and few monomorphic markers (1.4%-4.0%) however, some recovered L. nannotis populations had low N
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.
Publisher: Wiley
Date: 09-2014
DOI: 10.1002/ECE3.1199
Publisher: Microbiology Society
Date: 05-2020
DOI: 10.1099/MIC.0.000904
Abstract: There is increasing recognition that microbiomes are important for host health and ecology, and understanding host microbiomes is important for planning appropriate conservation strategies. However, microbiome data are lacking for many taxa, including turtles. To further our understanding of the interactions between aquatic microbiomes and their hosts, we used next generation sequencing technology to examine the microbiomes of the Krefft’s river turtle ( Emydura macquarii krefftii ). We examined the microbiomes of the buccal (oral) cavity, skin on the head, parts of the shell with macroalgae and parts of the shell without macroalgae. Bacteria in the phyla Proteobacteria and Bacteroidetes were the most common in most s les (particularly buccal s les), but Cyanobacteria , Deinococcus-thermus and Chloroflexi were also common (particularly in external microbiomes). We found significant differences in community composition among each body area, as well as significant differences among in iduals. The buccal cavity had lower bacterial richness and evenness than any of the external microbiomes, and it had many licon sequence variants (ASVs) with a low relative abundance compared to other body areas. Nevertheless, the buccal cavity also had the most unique ASVs. Parts of the shell with and without algae also had different microbiomes, with particularly obvious differences in the relative abundances of the families Methylomonaceae , Saprospiraceae and Nostocaceae . This study provides novel, baseline information about the external microbiomes of turtles and is a first step in understanding their ecological roles.
Publisher: Brill
Date: 2007
DOI: 10.1163/156853807781374755
Abstract: To gain information on the microhabitat use, home range and movement of a species, it is often necessary to remotely track in iduals in the field. Radio telemetry is commonly used to track hibians, but can only be used on relatively large in iduals. Harmonic direction finding can be used to track smaller animals, but its effectiveness has not been fully evaluated. Tag attachment can alter the behaviour of hibians, suggesting that data obtained using either technique may be unreliable. We investigated the effects of external tag attachment on behaviour in the laboratory by observing 12 frogs for five nights before and five nights after tag attachment, allowing one night to recover from handling. Tag attachment did not affect distance moved or number of times moved, indicating that the effects of tag attachment are unlikely to persist after the first night following attachment. We then compared harmonic direction finding and radio-telemetry using data collected in the field. We fitted rainforest stream frogs of three species with tags of either type, located them diurnally and nocturnally for approximately two weeks, and compared movement parameters between techniques. In the field, we obtained fewer fixes on frogs using harmonic direction finding, but measures of movement and habitat use did not differ significantly between techniques. Because radio telemetry makes it possible to locate animals more consistently, it should be preferred for animals large enough to carry radio tags. If harmonic direction finding is necessary, it can produce reliable data, particularly for relatively sedentary species.
Publisher: Springer Science and Business Media LLC
Date: 19-03-2011
Publisher: Elsevier BV
Date: 10-2011
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.
Publisher: Inter-Research Science Center
Date: 08-02-2007
DOI: 10.3354/DAO074007
Abstract: Chytridiomycosis is a potentially fatal disease of hibians caused by Batrachochytrium dendrobatidis, and is implicated in declines and extinctions of hibian populations and species around the world. To cause local host extinction, a disease organism must persist at low host densities. One mechanism that could facilitate this is the ability to persist in the environment. In the laboratory, B. dendrobatidis spreads by both frog-to-frog and environment-to-frog transmission, and can persist on a number of biotic substrates. In the field, B. dendrobatidis has been detected on environmental s les taken during an epidemic, but it is not known if it persists in the environment when endemic. Retreat sites of 2 species of Australian rain forest stream frogs Litoria lesueuri and L. nannotis were s led 0 to 3 d after occupation during the wet and dry seasons in northern Queensland, Australia, where chytridiomycosis has been endemic for at least 10 yr. The intensity and prevalence of infection in frogs during s ling were comparatively low compared with epidemics. Diagnostic quantitative polymerase chain reaction did not detect B. dendrobatidis in any retreat site s les. It thus appears that retreat sites are not a major environmental source of infection when B. dendrobatidis occurs at low prevalence and intensity on frogs. This suggests that control efforts may not need to eliminate the organism from the environment, at least when prevalence and intensity of infection are low in frogs. Simply treating hosts may be effective at controlling the disease in the wild.
Publisher: Public Library of Science (PLoS)
Date: 04-09-2013
Publisher: Wiley
Date: 09-04-2009
Publisher: Springer Science and Business Media LLC
Date: 21-08-2015
DOI: 10.1038/SREP13472
Abstract: Natural disturbances can drive disease dynamics in animal populations by altering the microclimates experienced by hosts and their pathogens. Many pathogens are highly sensitive to temperature and moisture and therefore small changes in habitat structure can alter the microclimate in ways that increase or decrease infection prevalence and intensity in host populations. Here we show that a reduction of rainforest canopy cover caused by a severe tropical cyclone decreased the risk of endangered rainforest frogs ( Litoria rheocola ) becoming infected by a fungal pathogen ( Batrachochytrium dendrobatidis ). Reductions in canopy cover increased the temperatures and rates of evaporative water loss in frog microhabitats, which reduced B. dendrobatidis infection risk in frogs by an average of 11–28% in cyclone-damaged areas, relative to unaffected areas. Natural disturbances to the rainforest canopy can therefore provide an immediate benefit to frogs by altering the microclimate in ways that reduce infection risk. This could increase host survival and reduce the probability of epidemic disease outbreaks. For hibian populations under immediate threat from this pathogen, targeted manipulation of canopy cover could increase the availability of warmer, drier microclimates and therefore tip the balance from host extinction to coexistence.
Publisher: Wiley
Date: 06-09-2005
Publisher: Wiley
Date: 22-11-2019
Publisher: Elsevier BV
Date: 10-1994
Publisher: Wiley
Date: 08-09-2011
DOI: 10.1111/J.1523-1739.2011.01728.X
Abstract: Species that are tolerant of broad environmental gradients may be less vulnerable to epizootic outbreaks of disease. Chytridriomycosis, caused by the fungus Batrachochytrium dendrobatidis, has been linked to extirpations and extinctions of hibian species in many regions. The pathogen thrives in cool, moist environments, and high hibian mortality rates have commonly occurred during chytridiomycosis outbreaks in hibian populations in high-elevation tropical rainforests. In Australia several high-elevation species, including the armored mist frog (Litoria lorica), which is designated as critically endangered by the International Union for the Conservation of Nature (IUCN), were believed to have gone extinct during chytridiomycosis outbreaks in the 1980s and early 1990s. Species with greater elevational ranges disappeared from higher elevations, but remained common in the lowlands. In June 2008, we surveyed a stream in a high-elevation dry sclerophyll forest and discovered a previously unknown population of L. lorica and a population of the waterfall frog (Litoria nannotis). We conducted 6 additional surveys in June 2008, September 2008, March 2009, and August 2009. Prevalences of B. dendrobatidis infection (number infected per total s led) were consistently high in frogs (mean 82.5%, minimum 69%) of both species and in tadpoles (100%) during both winter (starting July) and summer (starting February). However, no in iduals of either species showed clinical signs of disease, and they remained abundant (3.25 - 8.75 in iduals of L. lorica and 6.5-12.5 in iduals of L. nannotis found erson/100 m over 13 months). The high-elevation dry sclerophyll site had little canopy cover, low annual precipitation, and a more defined dry season than a nearby rainforest site, where L. nannotis was more negatively affected by chytridiomycosis. We hypothesize this lack of canopy cover allowed the rocks on which frogs perched to warm up, thereby slowing growth and reproduction of the pathogen on the hosts. In addition, we suggest surveys for apparently extinct or rare species should not be limited to core environments.
Publisher: Inter-Research Science Center
Date: 2003
DOI: 10.3354/DAO055065
Abstract: The emerging infectious disease chytridiomycosis is thought to have contributed to many of the recent alarming declines in hibian populations. Mortalities associated with these declines have often occurred during cooler seasons and at high elevations, suggesting that environmental temperature may be an important factor in disease emergence. We found that thermal environment affects the progress of the disease, and that housing frogs Litoria chloris at an environmental temperature of 37 degrees C for less than 16 h can clear them of the chytrid pathogen Batrachochytrium dendrobatidis. Our experiment demonstrated that elevated body temperatures similar to those experienced in behavioral fever and during normal thermoregulation can clear frogs of chytrid infection therefore, variation in thermoregulatory opportunities and behaviors are likely to contribute to the differences in disease incidence observed among host species, populations, and regions. Although further refinement of the technique is needed to encompass various host species, appropriately applied thermal manipulations of hibians and their enclosures may prove to be a safe and effective way of eliminating the fungal pathogen from captive hibian populations and: preventing accidental spread of the pathogen when animals are translocated or released from captivity.
Publisher: Wiley
Date: 25-12-2018
DOI: 10.1111/AEC.12570
Publisher: Wiley
Date: 14-07-2015
DOI: 10.1111/AEC.12287
Publisher: University of Chicago Press
Date: 05-1993
DOI: 10.1086/285501
Abstract: Species that reach the end of a life-history stage (transform) at relatively fixed sizes may often grow nonasymptotically before transforming. Many species of squid and at least some larval frogs, fish, and insects appear to follow this pattern. When data on body size at a range of ages are available for such taxa, they are often described well by exponential curves or by power curves that are concave upward. When such data are transformed to mean sizes for ages or age classes, they are likely to fit asymptotic growth models such as the logistic and Gompertz curves. These curves are good descriptions of the behavior of the population mean but poor descriptions of the pattern followed by any in idual in the population. Analyzing and presenting data on size at age using mean sizes can thus lead to incorrect interpretations of growth patterns and should be avoided.
Publisher: University of Chicago Press
Date: 1988
DOI: 10.1086/284775
Publisher: CSIRO Publishing
Date: 1993
DOI: 10.1071/WR9930001
Abstract: We examined factors affecting the growth and survival of postmetamorphic Bufo marinus using s ling and experiments. Bufo metamorphs, defined as newly emerged terrestrial toads of 9-29mm snout-ischium length (SIL), were classified into four stages on the basis of colour and size. Stage 1 were uniformly black and about 9-12 mm SIL, stage 2 were mottled with orange spots and about 12-16mm SL, stage 3 had a white mid-dorsal line and were about 16-25mm SIL, and stage 4 had enlarged parotoid glands and were about 25-29 mm SIL. We determined the density of each stage at three distances (0-1, 2-3, 4-5m) from their larval habitat using 1 x 1-m quadrat s les. The mean densities of all metamorphs within 1 m of water were 2.6m-2 and 2.1m-2 for the wet and early dry seasons, respectively. The mean densities of all metamorphs during both seasons at 2-3m and 4-5m from water were 0.8m-2 and 0.6m-2, respectively. Stage 2 metamorphs were most common in s les. Most stage 1 metamorphs occurred within 1m of the water in both seasons (98% wet 95% dry). Increasing percentages of stage 2, 3 and 4 metamorphs occurred in s les 2-3 and 4-5m from water (38, 49 and 80%, respectively, averaged over both seasons). Three experiments examined the response of metamorph growth and survival rates to density in open-topped flyscreen enclosures. Stage 1 or 2 metamorphs were established at initial densities of 3.3, 6.7 and 16.7m-2. Metamorphs in the lower-density enclosures grew more rapidly than metamorphs in the higher-density enclosures. A profile analysis showed that daily survival rate was not densitydependent. Correlation analyses showed that daily metamorph survival was influenced by daily maximum and minimum temperatures. Metamorphs at lower densities attain juvenile size (30mm) more rapidly because they survive at the same daily rates as metamorphs at higher densities they experience lower cumulative mortality as metamorphs.
Publisher: Springer Science and Business Media LLC
Date: 06-2020
Publisher: The Royal Society
Date: 11-01-2012
Abstract: It is well known in ecology, evolution and medicine that both the nature (commensal, parasitic and mutualistic) and outcome (symbiont fitness, survival) of symbiotic interactions are often context-dependent. Less is known about the importance of context-dependence in symbioses involved in wildlife disease. We review variable symbioses, and use the hibian disease chytridiomycosis to demonstrate how understanding context-dependence can improve the understanding and management of wildlife diseases. In chytridiomycosis, the host–pathogen interaction is context-dependent it is strongly affected by environmental temperature. Skin bacteria can also modify the interaction some bacteria reduce hibians' susceptibility to chytridiomycosis. Augmentation of protective microbes is being considered as a possible management tool, but informed application of bioaugmentation requires understanding of how the interactions between host, beneficial bacteria and pathogen depend upon environmental context. The community-level response of the hibian skin microbiota to environmental conditions may explain the relatively narrow range of environmental conditions in which past declines have occurred. Environmental context affects virulence and the protection provided by mutualists in other host–pathogen systems, including threatened bats and corals. Increased focus on context-dependence in interactions between wildlife and their symbionts is likely to be crucial to the future investigation and management of emerging diseases of wildlife.
Publisher: Herpetologists League
Date: 06-2015
Publisher: American Association for the Advancement of Science (AAAS)
Date: 23-10-2009
Abstract: The global hibian decline has been attributed, among other causes, to an hibian skin disease chytridiomycosis caused by the fungus Batrachochytrium dendrobatidis . However, how this pathogen causes mortality has been unclear. Voyles et al. (p. 582 ) show that this superficial skin infection may lead to cardiac failure owing to changes caused by lowered ion transport through the skin and consequent electrolyte reduction in the blood.
Publisher: Inter-Research Science Center
Date: 24-09-2008
DOI: 10.3354/DAO01958
Abstract: Batrachochytrium dendrobatidis (Bd) causes chytridiomycosis, which has caused devastating hibian population declines. Little is known about the biology of Bd on hosts, and techniques for diagnosing it on living and preserved animals are still evolving. We investigated the spatial distribution of Bd on the integument of naturally infected Australian hylid frogs Litoria genimaculata at 4 rain forest localities in northern Queensland, Australia. We collected 555 s les by swabbing 111 in iduals on 5 regions of the body (back, abdomen, legs, forefeet and hindfeet). Numbers of zoospore equivalents on each body region were quantified using a real-time TaqMan PCR assay. The intensity of infection differed significantly among body regions and this pattern of differences differed among s ling localities. The lightest infections were usually centered on the abdomen, while heavier infections were concentrated on the legs and feet. The back was always either lightly infected or uninfected. Many frogs with light infections had positive PCR results only for the abdomen or the legs. We compared swabs taken from the legs and abdomen and found that they provided similar sensitivity to detect infections, but using both regions together led to greater sensitivity than either region alone. Because swabbing may transfer zoospores from infected to uninfected regions within in iduals, we suggest that the best procedure for all species is to employ separate swabs for each body region. If that cannot be done, swabbing patterns that minimize potential harm should be determined for each species, and possibly each class of in iduals (e.g. males, females, juveniles) within species, by examining the distribution of infection among body parts in naturally infected in iduals.
Publisher: Springer Science and Business Media LLC
Date: 21-03-2013
DOI: 10.1038/SREP01515
Publisher: JSTOR
Date: 18-12-1992
DOI: 10.2307/1446653
Publisher: Wiley
Date: 02-1989
DOI: 10.2307/1938427
Publisher: Springer Science and Business Media LLC
Date: 20-08-2018
DOI: 10.1038/S41598-018-30099-0
Abstract: Loss of fitness can be a consequence of selection for rapid dispersal ability in invasive species. Increased prevalence of spinal arthritis may occur in cane toad populations at the invasion front as a cost of increased invasiveness, but our knowledge of the ecological drivers of this condition is lacking. We aimed to determine the factors explaining the prevalence of spinal arthritis in populations across the Australian landscape. We studied populations across a gradient of invasion histories. We collected 2415 toads over five years and determined the presence and size of spondylosis for each in idual. We examined the effect of host size, leg length and invasion history on the prevalence of spondylosis. Host size was a significant predictor of spondylosis across populations. Contrary to our expectation, the overall prevalence of spondylosis was not positively related to invasion history and did not correlate with toad relative leg length. Rather than invasion age, the latitude at which populations were s led provided an alternate explanation for the prevalence of spondylosis in cane toad populations and suggested that the incidence of this condition did not increase as a physiological cost of invasion, but is instead related to physical variables, such as climate.
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.JTHERBIO.2019.102472
Abstract: 1. The course and outcome of many wildlife diseases are context-dependent, and therefore change depending on the behaviour of hosts and environmental response of the pathogen. 2. Contemporary declines in hibian populations are widely attributed to chytridiomycosis, caused by the pathogenic fungus Batrachochytrium dendrobatidis. Despite the thermal sensitivity of the pathogen and its hibian hosts, we do not understand how host thermal regimes experienced by frogs in the wild directly influence pathogen growth. 3. We tested how thermal regimes experienced by the rainforest frog Litoria rheocola in the wild influence pathogen growth in the laboratory, and whether these responses differ from pathogen growth under available environmental thermal regimes. 4. Frog thermal regimes mimicked in the laboratory accelerated pathogen growth during conditions representative of winter at high elevations more so than if temperatures matched air or stream water temperatures. By contrast, winter frog thermal regimes at low elevations slowed pathogen growth relative to air temperatures, but not water temperatures. 5. The growth pattern of the fungus under frog thermal regimes matches field prevalence and intensity of infections for this species (high elevation winter > high elevation summer > low elevation winter > low elevation summer), whereas pathogen growth trajectories under environmental temperatures did not match these patterns. 6. If these laboratory results translate into field responses, tropical frogs may be able to reduce disease impacts by regulating their body temperatures to limit pathogen growth (e.g., by using microhabitats that facilitate basking to reach high temperatures) in other cases, the environment may limit the ability of frogs to thermoregulate such that in iduals are more vulnerable to this pathogen (e.g., in dense forests at high elevations). 7. Species-specific thermoregulatory behaviour, and interactions with and constraints imposed by the environment, are therefore essential to understanding and predicting the spatial and temporal impacts of this global disease.
Publisher: Inter-Research Science Center
Date: 13-08-2007
DOI: 10.3354/DAO01830
Abstract: The hibian disease chytridiomycosis, caused by the pathogen Batrachochytrium dendrobatidis, has been implicated in mass mortalities, population declines and extinctions of hibians around the world. In almost all cases, hibian species that have disappeared or declined due to chytridiomycosis coexist with non-declining species. One reason why some species decline from chytridiomycosis and others do not may be interspecific differences in behaviour. Host behaviour could either facilitate or hinder pathogen transmission, and transmission rates in the field are likely to vary among species according the frequency of factors such as physical contact between frogs, contact with infected water and contact with environmental substrates containing B. dendrobatidis. We tracked 117 frogs (28 Litoria nannotis, 27 L. genimaculata and 62 L. lesueuri) at 5 sites where B. dendrobatidis is endemic in the rainforest of tropical northern Queensland and recorded the frequency of frog-to-frog contact and the frequency of contact with stream water and environmental substrates. Frequency of contact with other frogs and with water were highest in L. nannotis, intermediate in L. genimaculata and lowest in L. lesueueri. Environmental substrate use also differed among species. These species-specific opportunities for disease transmission were correlated with conservation status: L. nannotis is the species most susceptible to chytridiomycosis-related declines and L. lesueuri is the least susceptible. Interspecific variation in transmission probability may, therefore, play a large role in determining why chytridiomycosis drives some populations to extinction and not others.
Publisher: Inter-Research Science Center
Date: 28-01-2009
DOI: 10.3354/DAO02004
Abstract: Chytridiomycosis, caused by the skin fungus Batrachochytrium dendrobatidis (Bd), has caused population declines of many hibians in remote protected habitats. Progress has been made in understanding the pathogen's life cycle, documenting its devastating effects on in idual hibians and on populations, and understanding how and why disease outbreaks occur. No research has directly addressed the critical question of how to prevent declines and extinctions caused by outbreaks of the disease. We have identified a number of bacterial species of hibian skin that inhibit Bd in vitro. Here, we demonstrate that a species of anti-Bd skin bacteria can be successfully added to skins of salamanders Plethodon cinereus, and that addition of this bacterium reduced the severity of a disease symptom in experimentally infected in iduals. This is the first demonstration that manipulating the natural skin microbiota of an hibian species can alter the pathogen's negative effects on infected hibians and appears to be the first demonstration that an epibiotic manipulation of any wildlife species can lessen the effects of an emerging infectious disease. It suggests that probiotic or bio-augmentation manipulations of cutaneous microbiota could have the potential to reduce susceptibility of hibians to the disease in nature. This is the first approach suggested that could slow or halt epidemic outbreaks and allow successful reintroductions of hibian species that have become locally or globally extinct in the wild. Our results also suggest a mechanism for the association of climate change and the likelihood of chytridiomycosis outbreaks via the effects of the former on antifungal bacterial communities.
Publisher: JSTOR
Date: 09-05-1986
DOI: 10.2307/1444999
Publisher: Elsevier BV
Date: 12-2012
DOI: 10.1016/J.FUNBIO.2012.10.005
Abstract: Many parasites and pathogens suppress host immunity to maintain infection or initiate disease. On the skin of many hibians, defensive peptides are active against the fungus Batrachochytrium dendrobatidis (Bd), the causative agent of the emerging infectious disease chytridiomycosis. We tested the hypothesis that infection with the fungus may be linked to lower levels of defensive peptides. We s led both ambient (or constitutive) skin peptides on the ventral surface immediately upon capture, and stored skin peptides induced from granular glands by norepinephrine administration of Australian green-eyed treefrogs, Litoria serrata. Upon capture, uninfected frogs expressed an array of antimicrobial peptides on their ventral surface, whereas infected frogs had reduced skin peptide expression. Expression of ambient skin peptides differed with infection status, and antimicrobial peptides maculatin 1.1 and 2.1 were on average three times lower on infected frogs. However, the repertoire of skin peptides stored in granular glands did not differ with infection status on average equal quantities were recovered from infected and from uninfected frogs. Our results could have at least two causes: (1) frogs with reduced peptide expression are more likely to become infected (2) Bd infection interferes with defence peptides by inhibiting release or causing selective degradation of peptides on the skin surface. Immune evasion therefore may contribute to the pathogenesis of chytridiomycosis and a mechanistic understanding of this fungal strategy may lead to improved methods of disease control.
Publisher: Wiley
Date: 14-08-2017
Publisher: Wiley
Date: 15-11-2017
DOI: 10.1002/ECY.2019
Publisher: Wiley
Date: 20-07-2010
Publisher: Wiley
Date: 03-06-2019
DOI: 10.1002/FEE.2057
Publisher: Wiley
Date: 04-1998
Publisher: Wiley
Date: 12-08-1997
Publisher: Inter-Research Science Center
Date: 12-09-2012
DOI: 10.3354/DAO02494
Abstract: The emerging infectious disease chytridiomycosis has been implicated in declines and disappearances of hibian populations around the world. However, susceptibility to infection and the extent of pathological effects of infection vary among hosts, and species with life histories that include parental care of direct-developing terrestrial eggs may tend to be less susceptible. We examined s les from a total of 595 in iduals of 9 species of direct-developing Australian frogs in the family Microhylidae for the presence of infection by Batrachochytrium dendrobatidis (Bd). Between 1995 and 2004, 336 s les were collected 102 of these were analysed histologically and 234 were tissues stored in alcohol, which were examined using diagnostic quantitative PCR (qPCR). Swab s les were collected from 259 frogs from 2005 to 2008 and were examined using qPCR. None of the 595 s les showed evidence of infection by Bd. If these data are regarded as a single s le representative of Australian microhylids, the upper 95% binomial confidence limit for the prevalence of infection in frogs of this family is 0.0062 (<1%). Even if only the data from the more powerful diagnostic qPCR tests are used, the upper 95% confidence limit for prevalence is 0.0075 (<1%). Our data suggest that Australian microhylids have a very low prevalence of infection by Bd in nature, and thus are either not susceptible, or are only slightly susceptible, to chytridiomycosis. This could be due solely to, or in combination with, low rates of transmission and to factors that promote resistance to infection, including ecological or behavioural characteristics, innate immune functions such as antimicrobial skin peptides, or antimicrobial symbionts in skin flora.
Publisher: Springer Science and Business Media LLC
Date: 22-06-2016
DOI: 10.1038/SREP28158
Abstract: Advertisement calls tend to differ among populations, based on morphological and environmental factors, or simply geographic distance, in many taxa. Invasive cane toads ( Rhinella marina ) were introduced to Australia in 1935 and their distribution has expanded at increasing rates over time. Rapid evolution occurred in morphological and behavioural characters that accelerate dispersal, but the effects of rapid expansion on sexual signals have not been examined. We collected advertisement calls from four populations of different ages since invasion and analysed the geographic differentiation of seven call parameters. Our comparisons indicate that the calls of R. marina differ among Australian populations. The signal variation was not simply clinal with respect to population age, climate, or morphological differentiation. We suggest that selection on signalling among populations has been idiosyncratic and may reflect local female preferences or adaptation to environmental factors that are not clinal such as energy availability.
Publisher: Wiley
Date: 04-08-2012
DOI: 10.1002/ECE3.334
Publisher: Oxford University Press (OUP)
Date: 02-10-2003
Publisher: JSTOR
Date: 03-1989
DOI: 10.2307/3565293
Publisher: Springer Science and Business Media LLC
Date: 04-01-2006
Publisher: Springer Science and Business Media LLC
Date: 14-10-2009
DOI: 10.1007/S00442-008-1167-Y
Abstract: Invasive species are widely viewed as unmitigated ecological catastrophes, but the reality is more complex. Theoretically, invasive species could have negligible or even positive effects if they sufficiently reduce the intensity of processes regulating native populations. Understanding such mechanisms is crucial to predicting ultimate ecological impacts. We used a mesocosm experiment to quantify the impact of eggs and larvae of the introduced cane toad (Bufo marinus) on fitness-related traits (number, size and time of emergence of metamorphs) of a native Australian frog species (Opisthodon ornatus). The results depended upon the timing of oviposition of the two taxa, and hence the life-history stages that came into contact. Growth and survival of O. ornatus tadpoles were enhanced when they preceded B. marinus tadpoles into ponds, and reduced when they followed B. marinus tadpoles into ponds, relative to when tadpoles of both species were added to ponds simultaneously. The dominant tadpole-tadpole interaction is competition, and the results are consistent with competitive priority effects. However, these priority effects were reduced or reversed when O. ornatus tadpoles encountered B. marinus eggs. Predation on toxic toad eggs reduced the survival of O. ornatus and B. marinus. The consequent reduction in tadpole densities allowed the remaining O. ornatus tadpoles to grow more rapidly and to metamorphose at larger body sizes (>60% disparity in mean mass). Thus, exposure to B. marinus eggs reduced the number of O. ornatus metamorphs, but increased their body sizes. If the increased size at metamorphosis more than compensates for the reduced survival, the effective reproductive output of native anurans may be increased rather than decreased by the invasive toad. Minor interspecific differences in the seasonal timing of oviposition thus have the potential to massively alter the impact of invasive cane toads on native anurans.
Publisher: Inter-Research Science Center
Date: 20-08-2015
DOI: 10.3354/DAO02898
Abstract: The highly virulent fungal pathogen Batrachochytrium dendrobatidis (Bd) poses a global threat to hibian bio ersity. Streams and other water bodies are central habitats in the ecology of the disease, particularly in rainforests where they may transport and transmit the pathogen and harbor infected tadpoles that serve as reservoir hosts. We conducted an experiment using larval green-eyed tree frogs Litoria serrata in semi-natural streamside channels to test the hypotheses that (1) the fungus can be transmitted downstream in stream habitats and (2) infection affects tadpole growth and mouthpart loss. Our results showed that transmission can occur downstream in flowing water with no contact between in iduals, that newly infected tadpoles suffered increased mouthpart loss in comparison with controls that were never infected and that infected tadpoles grew at reduced rates. Although recently infected tadpoles showed substantial loss of mouthparts, in iduals with longstanding infections did not, suggesting that mouthparts may re-grow following initial loss. Our study suggests that any management efforts that can reduce the prevalence of infections in tadpoles may be particularly effective if applied in headwater areas, as their effects are likely to be felt downstream.
Publisher: Wiley
Date: 10-10-2005
Publisher: The Royal Society
Date: 07-07-2015
Abstract: To minimize the negative effects of an infection on fitness, hosts can respond adaptively by altering their reproductive effort or by adjusting their timing of reproduction. We studied effects of the pathogenic fungus Batrachochytrium dendrobatidis on the probability of calling in a stream-breeding rainforest frog ( Litoria rheocola ). In uninfected frogs, calling probability was relatively constant across seasons and body conditions, but in infected frogs, calling probability differed among seasons (lowest in winter, highest in summer) and was strongly and positively related to body condition. Infected frogs in poor condition were up to 40% less likely to call than uninfected frogs, whereas infected frogs in good condition were up to 30% more likely to call than uninfected frogs. Our results suggest that frogs employed a pre-existing, plastic, life-history strategy in response to infection, which may have complex evolutionary implications. If infected males in good condition reproduce at rates equal to or greater than those of uninfected males, selection on factors affecting disease susceptibility may be minimal. However, because reproductive effort in infected males is positively related to body condition, there may be selection on mechanisms that limit the negative effects of infections on hosts.
Publisher: Wiley
Date: 06-2014
DOI: 10.1890/13-0693.1
Abstract: Sexual differences in adult body size (sexual size dimorphism, or SSD) ultimately can be favored by selection because larger males are more likely to be successful competitors for females, because larger females bear larger clutches, or because intersexual size differences reduce resource competition. Natural selection during juvenile development can influence sexual dimorphism of adults, and selection on adults and juveniles may differ. Studies that address the relative contributions of adult body shape dimorphism and sexually dimorphic patterns of growth and maturity are particularly useful in understanding the evolution of size dimorphism, yet they are rare. We investigated three sympatric, congeneric lizard species with different degrees and directions of adult sexual dimorphism and compared their growth patterns, survival probabilities, and intersexual trophic niche differences. Different mechanisms, even within these closely related, sympatric species, acted on juvenile lizards to produce species differences in adult SSD. Both degree and direction of dimorphism resulted from differences between the sexes in either the duration of growth or the rate of growth, but not from differences in rates of survival or selection on juvenile growth rate. Species‐ and sex‐specific trade‐offs in the allocation of energy to growth and reproduction, as well as differential timing of maturation, thus caused the growth patterns of the sexes to erge, producing SSD. The differences that we observed in the direction of SSD among these species is consistent with their different social systems, suggesting that differential selection on adult body size has been responsible for the observed species‐specific differences in juvenile growth rates and maturational timing.
Publisher: Springer Science and Business Media LLC
Date: 21-08-2015
DOI: 10.1007/S00442-015-3422-3
Abstract: Pathogens can drive host population dynamics. Chytridiomycosis is a fungal disease of hibians that is caused by the fungus Batrachochytrium dendrobatidis (Bd). This pathogen has caused declines and extinctions in some host species whereas other host species coexist with Bd without suffering declines. In the early 1990s, Bd extirpated populations of the endangered common mistfrog, Litoria rheocola, at high-elevation sites, while populations of the species persisted at low-elevation sites. Today, populations have reappeared at many high-elevation sites where they presently co-exist with the fungus. We conducted a capture-mark-recapture (CMR) study of six populations of L. rheocola over 1 year, at high and low elevations. We used multistate CMR models to determine which factors (Bd infection status, site type, and season) influenced rates of frog survival, recapture, infection, and recovery from infection. We observed Bd-induced mortality of in idual frogs, but did not find any significant effect of Bd infection on the survival rate of L. rheocola at the population level. Survival and recapture rates depended on site type and season. Infection rate was highest in winter when temperatures were favourable for pathogen growth, and differed among site types. The recovery rate was high (75.7-85.8%) across seasons, and did not differ among site types. The coexistence of L. rheocola with Bd suggests that (1) frog populations are becoming resistant to the fungus, (2) Bd may have evolved lower virulence, or (3) current environmental conditions may be inhibiting outbreaks of the fatal disease.
Publisher: University of Chicago Press
Date: 03-2019
DOI: 10.1086/701673
Publisher: Public Library of Science (PLoS)
Date: 20-03-2015
Publisher: Elsevier BV
Date: 02-2010
Publisher: Herpetologists League
Date: 03-2014
Publisher: JSTOR
Date: 06-06-1980
DOI: 10.2307/1563851
Publisher: Springer Science and Business Media LLC
Date: 12-2011
DOI: 10.1038/480461A
Publisher: Wiley
Date: 10-06-2010
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/ZO03036
Abstract: We studied a population of the rainforest frog Litoria genimaculata over a 7-year period at Birthday Creek, an upland rainforest stream in northern Queensland. Estimated population size on a 60-m transect fluctuated seasonally, decreasing to zero during most winters and reaching a maximum of over 130 during most warmer spring and summer months with an influx of young adult males. Summer population estimates were much smaller during 1990–93, coinciding with the disappearance of two sympatric species. However the L. genimaculata population subsequently recovered to pre-‘decline’ levels. Females were rarely captured along the stream so the operational sex ratio of adult frogs was strongly biased in favour of males (overall sex ratio 1 : 0.04). Sexual dimorphism in this species is extreme. The mean weight of gravid females (23.35 g) was nearly five times that of males (4.68 g) and the ratio of female SVL to male SVL was 1.65. Reproductive and fat-body condition changed seasonally, with males reaching peak reproductive condition in late spring and summer when population densities were greatest. Our data suggest that Litoria genimaculata uses Birthday Creek largely or exclusively as a reproductive habitat. The extent to which this species uses habitats away from stream environments remains to be determined.
Publisher: Oxford University Press (OUP)
Date: 08-2000
Publisher: Wiley
Date: 06-2008
DOI: 10.1890/06-1842.1
Abstract: Life-history trade-offs allow many animals to maintain reproductive fitness across a range of climatic conditions. When used by parasites and pathogens, these strategies may influence patterns of disease in changing climates. The chytrid fungus, Batrachochytrium dendrobatidis, is linked to global declines of hibian populations. Short-term growth in culture is maximal at 17 degrees-25 degrees C. This has been used in an argument that global warming, which increases the time that hibians spend at these temperatures in cloud-covered montane environments, has led to extinctions. Here we show that the hibian chytrid responds to decreasing temperatures with trade-offs that increase fecundity as maturation rate slows and increase infectivity as growth decreases. At 17 degrees-25 degrees C, infectious zoospores encyst (settle and develop a cell wall) and develop into the zoospore-producing stage (zoosporangium) faster, while at 7 degrees-10 degrees C, greater numbers of zoospores are produced per zoosporangium these remain infectious for a longer period of time. We modeled the population growth of B. dendrobatidis through time at various temperatures using delayed differential equations and observational data for four parameters: developmental rate of thalli, fecundity, rate of zoospore encystment, and rate of zoospore survival. From the models, it is clear that life-history trade-offs allow B. dendrobatidis to maintain a relatively high long-term growth rate at low temperatures, so that it maintains high fitness across a range of temperatures. When a seven-day cold shock is simulated, the outcome is intermediate between the two constant temperature regimes, and in culture, a sudden drop in temperature induces zoospore release. These trade-offs can be ecologically important for a variety of organisms with complex life histories, including pathogenic microorganisms. The effect of temperature on hibian mortality will depend on the interaction between fungal growth and host immune function and will be modified by host ecology, behavior, and life history. These results demonstrate that B. dendrobatidis populations can grow at high rates across a broad range of environmental temperatures and help to explain why it is so successful in cold montane environments.
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/WR06173
Abstract: Cane toads are an introduced pest in many tropical locations around the world, but, surprisingly, there are few methods available for their control. Highly effective trapping may provide a means of controlling toads, either alone or as part of an integrated pest-management scheme. Existing cane toad trap designs use lights to lure insects to traps, and toads enter the traps to feed. Using a large, outdoor experimental arena and playback of cane toad mating calls, we examined the possibility that cane toads, like many other anurans, are attracted to conspecific mating vocalisations. We found that both male and female toads were attracted to quiet (47dB(A) at 1 m) playbacks, whereas only males responded to loud (67dB(A) at 1 m) playbacks with phonotaxis. We also tested whether playbacks broadcast from traps would be useful attractants to traps in the field. We captured three times more toads in traps with playbacks than in traps without playbacks, suggesting that playbacks can be used to enhance trapping success for toads.
Publisher: JSTOR
Date: 06-1999
DOI: 10.2307/1565716
Publisher: Frontiers Media SA
Date: 18-07-2018
Publisher: Elsevier
Date: 2017
Publisher: Wiley
Date: 10-2005
Publisher: Annual Reviews
Date: 11-1999
DOI: 10.1146/ANNUREV.ECOLSYS.30.1.133
Abstract: ▪ Abstract Declines and losses of hibian populations are a global problem with complex local causes. These may include ultraviolet radiation, predation, habitat modification, environmental acidity and toxicants, diseases, changes in climate or weather patterns, and interactions among these factors. Understanding the extent of the problem and its nature requires an understanding of how local factors affect the dynamics of local populations. Hypotheses about population behavior must be tested against appropriate null hypotheses. We generated null hypotheses for the behavior of hibian populations using a model, and we used them to test hypotheses about the behavior of 85 time series taken from the literature. Our results suggest that most hibian populations should decrease more often than they increase, due to highly variable recruitment and less variable adult mortality. During the period covered by our data (1951–1997), more hibian populations decreased than our model predicted. However, there was no indication that the proportion of populations decreasing changed over time. In addition, our review of the literature suggests that many if not most hibians exist in metapopulations. Understanding the dynamics of hibian populations will require an integration of studies on and within local populations and at the metapopulation level.
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.
Publisher: Wiley
Date: 03-08-2001
Publisher: Elsevier BV
Date: 07-2012
Publisher: Society for the Study of Amphibians and Reptiles
Date: 12-2002
Publisher: Springer Science and Business Media LLC
Date: 04-10-2006
DOI: 10.1007/S00442-005-0228-8
Abstract: Many species of hibians in the wet tropics of Australia have experienced population declines linked with the emergence of a skin-invasive chytrid fungus, Batrachochytrium dendrobatidis. An innate defense, antimicrobial peptides produced by granular glands in the skin, may protect some species from disease. Here we present evidence that supports this hypothesis. We tested ten synthesized peptides produced by Australian species, and natural peptide mixtures from five Queensland rainforest species. Natural mixtures and most peptides tested in isolation inhibited growth of B. dendrobatidis in vitro. The three most active peptides (caerin 1.9, maculatin 1.1, and caerin 1.1) were found in the secretions of non-declining species (Litoria chloris, L. caerulea, and L. genimaculata). Although the possession of a potent isolated antimicrobial peptide does not guarantee protection from infection, non-declining species (L. lesueuri and L. genimaculata) inhabiting the rainforest of Queensland possess mixtures of peptides that may be more protective than those of the species occurring in the same habitat that have recently experienced population declines associated with chytridiomycosis (L. nannotis, L. rheocola, and Nyctimystes dayi). This study demonstrates that in vitro effectiveness of skin peptides correlates with the degree of decline in the face of an emerging pathogen. Further research is needed to assess whether this non-specific immune defense may be useful in predicting disease susceptibility in other species.
Publisher: Springer Science and Business Media LLC
Date: 07-02-2007
Publisher: Herpetologists League
Date: 12-2005
DOI: 10.1655/04-03.1
Publisher: Springer Science and Business Media LLC
Date: 24-08-2017
DOI: 10.1038/S41598-017-09950-3
Abstract: Unprecedented global climate change and increasing rates of infectious disease emergence are occurring simultaneously. Infection with emerging pathogens may alter the thermal thresholds of hosts. However, the effects of fungal infection on host thermal limits have not been examined. Moreover, the influence of infections on the heat tolerance of hosts has rarely been investigated within the context of realistic thermal acclimation regimes and potential anthropogenic climate change. We tested for effects of fungal infection on host thermal tolerance in a model system: frogs infected with the chytrid Batrachochytrium dendrobatidis . Infection reduced the critical thermal maxima (CT max ) of hosts by up to ~4 °C. Acclimation to realistic daily heat pulses enhanced thermal tolerance among infected in iduals, but the magnitude of the parasitism effect usually exceeded the magnitude of the acclimation effect. In ectotherms, behaviors that elevate body temperature may decrease parasite performance or increase immune function, thereby reducing infection risk or the intensity of existing infections. However, increased heat sensitivity from infections may discourage these protective behaviors, even at temperatures below critical maxima, tipping the balance in favor of the parasite. We conclude that infectious disease could lead to increased uncertainty in estimates of species’ vulnerability to climate change.
Publisher: Springer Science and Business Media LLC
Date: 03-01-2023
Publisher: Springer Science and Business Media LLC
Date: 11-01-2006
Publisher: Elsevier
Date: 2013
Publisher: Springer Science and Business Media LLC
Date: 18-01-2006
Publisher: Wiley
Date: 14-08-2007
Publisher: Public Library of Science (PLoS)
Date: 22-09-2014
Publisher: Elsevier BV
Date: 03-2016
Publisher: Springer Science and Business Media LLC
Date: 29-01-2013
DOI: 10.1038/NCLIMATE1812
Publisher: Springer Science and Business Media LLC
Date: 03-02-2012
DOI: 10.1007/S00442-012-2268-1
Abstract: Foraging theory suggests that predator responses to potential prey should be influenced by prey chemical defences, but the effects of ontogenetic variation in such defences on prey vulnerability to predators remain unclear. Cane toads (Rhinella marina) are toxic to anurophagous snakes, including the keelback (Tropidonophis mairii, a natricine colubrid that occurs within the toads' invasive range in Australia). Toxin levels and ersity change through toad ontogeny, decreasing from the egg stage to metamorphosis, then increasing in postmetamorphic toads. If the toxin content of a prey item influences predator responses, we predict that keelbacks should exhibit selective predation on toads close to metamorphosis. The results of our laboratory trials on adult (field-collected, and thus toad-experienced) and hatchling (laboratory-incubated, and thus toad-naive) keelbacks supported this prediction. The snakes selectively consumed later-stage rather than earlier-stage tadpoles, and earlier-stage rather than later-stage metamorphs. Our data are thus consistent with the hypothesis that ontogenetic changes in toxin content can affect in iduals' vulnerability to predation.
Publisher: Elsevier BV
Date: 11-2015
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/WR07014
Abstract: Amphibians are one of the most highly threatened groups of animals, but their effective conservation is h ered by a paucity of basic ecological knowledge, particularly for tropical stream-breeding species, in which declines have been most common and severe. We examined the movement patterns and habitat use of three stream-breeding frog species at five sites in northern Queensland, Australia. Movement and habitat use differed significantly among species. Litoria lesueuri moved more frequently and greater distances than did our other study species, and was often located away from streams, moving between intact rainforest and highly disturbed environments. Litoria genimaculata moved less frequently and shorter distances and was more restricted to stream environments compared with L. lesueuri, but was often located in the canopy. L. genimaculata occasionally moved large distances along and between streams, but was never located outside of intact rainforest. Litoria nannotis moved almost as frequently as the other species, but remained in streams during the day, did not move large distances along or between streams, and was always located within intact rainforest. Because of its sedentary behaviour, narrow habitat tolerance and affinity for stream environments, L. nannotis may be more vulnerable to extinction in human-modified landscapes compared with L. lesueuri and L. genimaculata.
Publisher: Inter-Research Science Center
Date: 13-12-2007
DOI: 10.3354/DAO01861
Abstract: Chytridiomycosis, caused by the pathogen Batrachochytrium dendrobatidis, is responsible for many hibian declines and has been identified in wild hibian populations on all continents where they exist, except for Asia. In order to assess whether B. dendrobatidis is present on the native hibians of Hong Kong, we s led wild populations of Amolops hongkongensis, Paa exilispinosa, P. spinosa and Rana chloronota during 2005-2006. Amphibians infected with B. dendrobatidis have been found in the international trade, so we also examined the extent and nature of the hibian trade in Hong Kong during 2005-2006, and assessed whether B. dendrobatidis was present in imported hibians. All 274 in iduals of 4 native hibian species s led tested negative for B. dendrobatidis, giving an upper 95% confidence limit for prevalence of 1.3%. Approximately 4.3 million hibians of 45 species from 11 countries were imported into Hong Kong via air over 12 mo we did not detect B. dendrobatidis on any of 137 imported hibians s led. As B. dendrobatidis generally occurs at greater than 5% prevalence in infected populations during favorable environmental conditions, native hibians in Hong Kong appear free of B. dendrobatidis, and may be at severe risk of impact if it is introduced. Until it is established that the pathogen is present in Hong Kong, management strategies should focus on preventing it from being imported and decreasing the risk of it escaping into the wild hibian populations if imported. Further research is needed to determine the status of B. dendrobatidis in Hong Kong with greater certainty.
Publisher: Wiley
Date: 24-10-2012
Publisher: Herpetologists League
Date: 12-2016
Publisher: Springer Science and Business Media LLC
Date: 14-07-2010
Publisher: Wiley
Date: 04-09-2019
DOI: 10.1111/JZO.12725
Publisher: Springer Science and Business Media LLC
Date: 09-2009
DOI: 10.1007/S10393-009-0266-5
Abstract: Relatively few studies of hibian diseases have employed standard ecological experimental designs. We discuss what constitutes a well-designed ecological experiment and encourage their use in disease studies. We illustrate how well-designed experiments can be used to determine the effects of pathogens on hibians and we illustrate how ancillary information, including that collected using molecular tools, can be used to enhance the value of such experiments.
Publisher: Proceedings of the National Academy of Sciences
Date: 30-09-2008
Abstract: Many animals modify their environments, apparently to reduce predation risk, but the success of such endeavors, and their impact on the density and distribution of populations, are rarely rigorously demonstrated. We staged a manipulative experiment to assess the effectiveness of self-made shelters by web spiders as protection from natural enemies. Scincid lizards were included or excluded from 21 replicated 200-m 2 plots, and spiders therein were classified as exposed or sheltered, depending on whether they were uncovered in their web or hidden in cocoons, leaves/debris, or burrows. We found that exposed spiders were greatly affected by the presence of predatory scincid lizards, whereas sheltered spiders were not. More specifically, lizards, which forage close to the ground, reduced the abundance of exposed spiders by two-thirds but had no effect on the abundance of sheltered spiders. Sheltered spiders were able to avoid predation and share space with lizards, suggesting that shelter construction is a mechanism for reducing predation risk and has important population consequences.
Publisher: Wiley
Date: 08-1985
DOI: 10.2307/1939162
Publisher: Society for the Study of Amphibians and Reptiles
Date: 06-2005
Publisher: Wiley
Date: 08-1985
DOI: 10.2307/1939161
Publisher: Wiley
Date: 08-08-2016
DOI: 10.1111/MEC.13754
Publisher: Inter-Research Science Center
Date: 13-03-2013
DOI: 10.3354/DAO02560
Abstract: Certain bacteria present on frog skin can prevent infection by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), conferring disease resistance. Previous studies have used agar-based in vitro challenge assays to screen bacteria for Bd-inhibitory activity and to identify candidates for bacterial supplementation trials. However, agar-based assays can be difficult to set up and to replicate reliably. To overcome these difficulties, we developed a semi-quantitative spectrophotometric challenge assay technique. Cell-free supernatants were prepared from filtered bacterial cultures and added to 96-well plates in replicated wells containing Bd zoospores suspended in tryptone-gelatin hydrolysate-lactose (TGhL) broth medium. Plates were then read daily on a spectrophotometer until positive controls reached maximum growth in order to determine growth curves for Bd. We tested the technique by screening skin bacteria from the Australian green-eyed tree frog Litoria serrata. Of bacteria tested, 31% showed some degree of Bd inhibition, while some may have promoted Bd growth, a previously unknown effect. Our cell-free supernatant challenge assay technique is an effective in vitro method for screening bacterial isolates for strong Bd-inhibitory activity. It contributes to the expanding field of bioaugmentation research, which could play a significant role in mitigating the effects of chytridiomycosis on hibians around the world.
Publisher: Wiley
Date: 10-11-2009
Publisher: Wiley
Date: 03-2002
Publisher: Wiley
Date: 12-01-2009
Publisher: JSTOR
Date: 04-1996
DOI: 10.2307/2389843
Publisher: Wiley
Date: 30-08-2016
Publisher: Proceedings of the National Academy of Sciences
Date: 15-02-2006
Abstract: Pathogens rarely cause extinctions of host species, and there are few ex les of a pathogen changing species richness and ersity of an ecological community by causing local extinctions across a wide range of species. We report the link between the rapid appearance of a pathogenic chytrid fungus Batrachochytrium dendrobatidis in an hibian community at El Copé, Panama, and subsequent mass mortality and loss of hibian bio ersity across eight families of frogs and salamanders. We describe an outbreak of chytridiomycosis in Panama and argue that this infectious disease has played an important role in hibian population declines. The high virulence and large number of potential hosts of this emerging infectious disease threaten global hibian ersity.
Publisher: Wiley
Date: 27-07-2016
DOI: 10.1002/ECE3.2256
Publisher: Springer Science and Business Media LLC
Date: 04-12-2000
Publisher: Wiley
Date: 02-05-2013
DOI: 10.1111/DDI.12091
Publisher: Inter-Research Science Center
Date: 19-06-2008
DOI: 10.3354/DAO01919
Abstract: Batrachochytrium dendrobatidis, an aquatic hibian fungus, has been implicated in many hibian declines and extinctions. A real-time polymerase chain reaction (PCR) TaqMan assay is now used to detect and quantify B. dendrobatidis on hibians and other substrates via tissue s les, swabbing and filtration. The extreme sensitivity of this diagnostic test makes it necessary to rigorously avoid cross-contamination of s les, which can produce false positives. One technique used to eliminate contamination is to destroy the contaminating DNA by chemical means. We tested 3 concentrations of sodium hypochlorite (NaOCl) (1, 6 and 12%) over 4 time periods (1, 6, 15 and 24 h) to determine if NaOCl denatures B. dendrobatidis DNA sufficiently to prevent its recognition and lification in PCR tests for the fungus. Soaking in 12% NaOCl denatured 100% of DNA within 1 h. Six percent NaOCl was on average 99.999% effective across all exposure periods, with only very low numbers of zoospores detected following treatment. One percent NaOCl was ineffective across all treatment periods. Under ideal, clean conditions treatment with 6% NaOCl may be sufficient to destroy DNA and prevent cross-contamination of s les however, we recommend treatment with 12% NaOCl for 1 h to be confident all B. dendrobatidis DNA is destroyed.
Publisher: Society for the Study of Amphibians and Reptiles
Date: 03-2002
Publisher: Wiley
Date: 03-1994
Publisher: CSIRO Publishing
Date: 1991
DOI: 10.1071/MF9910069
Abstract: The association between the sand dollar, Arachnoides placenta, and the eulimid gastropod, Hypermastus sp., was investigated at Pallarenda Beach, Townsville, Queensland. Hypermastus sp. is a temporary ectoparasite of A. placenta that penetrates the latter's test to ingest gonad tissue and coelomic fluid. The infestation rate normally varies between 8 and 15% but increases in winter to 26%. This seasonal increase in the infestation rate appears to be due to an increase in the duration of attachment of female parasites. Hypermastus sp. is sexually dimorphic, with males being, on average, 0.6 times the size of females. In iduals may be protandric sequential hermaphrodites.
Publisher: Brill
Date: 2019
DOI: 10.1163/15685381-20191168
Abstract: Declines due to fungal disease (chytridiomycosis) have affected many stream-dwelling frog species, especially in the tropics, leading to reduced abundance and ersity of their tadpoles. Studies in the Australian Wet Tropics have demonstrated that some frog species have declined or disappeared, while others have persisted. To assess the occurrence of stream-breeding frogs, we monitored tadpole populations of five frog species in Wet Tropics streams in the early 1990s (uplands, before chytridomycosis emergence), and in 2011-2013 (uplands and lowlands, after chytridiomycosis emergence), and investigated environmental factors that might influence tadpole abundance. Riffle-dwelling tadpoles of two frog species disappeared from the upland stream site during the 1990s, reflecting reported losses of adult populations. Tadpoles of one upland pool species initially declined but had recovered by 2011-2013. S les from the lowlands in 2011 to 2013 indicated no similar loss. Chytridiomycosis was the likely cause of changes in tadpole abundances between the two survey periods, given its known occurrence and documented effects on adult frogs in these systems however, we did not measure its prevalence in this study. Tadpole populations fluctuated seasonally, with abundances highest in spring and summer, reflecting the timing of frog reproduction. The most important biophysical influence on the assemblages that we measured was current velocity. Tadpole peak abundances suggest that they make a substantial contribution at the consumer level of food webs, and that their loss has altered food webs substantially in upland streams.
Publisher: Springer Science and Business Media LLC
Date: 18-04-2017
Publisher: Springer Science and Business Media LLC
Date: 08-07-2005
DOI: 10.1007/S00442-005-0177-2
Abstract: Intraclutch variation in offspring size should evolve when offspring encounter unpredictable environmental conditions. This form of bet-hedging should maximise the lifetime reproductive success of in iduals that engage it. We documented the numbers of eggs and means and variances of yolk volume in 15 frog species that occur in tropical savanna woodland. We experimentally determined the effects of initial yolk volume on larval growth patterns in four species. Intraclutch variation in yolk volume occurred to some degree in all species surveyed. Some species had very low, others had very high, intraclutch variation in yolk volume, but all species in which some clutches were highly variable also produced clutches with low variability. Species that occur in areas where the offspring environment is likely to be unpredictable had elevated levels of intraclutch variation in egg provisioning. There was no trade-off between egg size and number in any species surveyed. Under benign laboratory conditions, tadpoles from eggs with larger yolk volumes hatched at larger sizes, and these size differences persisted through a substantial proportion of the larval stage. This indicates that intraclutch variation in egg size has major offspring and thus parental fitness consequences, and is therefore a functional selection variable. This study provides evidence in support of models which predict that intraclutch variation in offspring provisioning can evolve in organisms that reproduce in unpredictable habitats.
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.JTHERBIO.2014.07.005
Abstract: Physical models are often used to estimate ectotherm body temperatures, but designing accurate models for hibians is difficult because they can vary in cutaneous resistance to evaporative water loss. To account for this variability, a recently published technique requires a pair of agar models that mimic hibians with 0% and 100% resistance to evaporative water loss the temperatures of these models define the lower and upper boundaries of possible hibian body temperatures for the location in which they are placed. The goal of our study was to develop a method for using these pairs of models to estimate parameters describing the distributions of body temperatures of frogs under field conditions. We radiotracked green-eyed treefrogs (Litoria serrata) and collected semi-continuous thermal data using both temperature-sensitive radiotransmitters with an automated datalogging receiver, and pairs of agar models placed in frog locations, and we collected discrete thermal data using a non-contact infrared thermometer when frogs were located. We first examined the accuracy of temperature-sensitive transmitters in estimating frog body temperatures by comparing transmitter data with direct temperature measurements taken simultaneously for the same in iduals. We then compared parameters (mean, minimum, maximum, standard deviation) characterizing the distributions of temperatures of in idual frogs estimated from data collected using each of the three methods. We found strong relationships between thermal parameters estimated from data collected using automated radiotelemetry and both types of thermal models. These relationships were stronger for data collected using automated radiotelemetry and impermeable thermal models, suggesting that in the field, L. serrata has a relatively high resistance to evaporative water loss. Our results demonstrate that placing pairs of thermal models in frog locations can provide accurate estimates of the distributions of temperatures experienced by in idual frogs, and that comparing temperatures from model pairs to direct measurements collected simultaneously on frogs can be used to broadly characterize the skin resistance of a species, and to select which model type is most appropriate for estimating temperature distributions for that species.
Publisher: CSIRO Publishing
Date: 1993
DOI: 10.1071/MF9930835
Abstract: The intertidal sand dollar Arachnoides placenta is parasitized by the eulimid Hypermastus placentae at Pallarenda Beach, Townsville, Queensland. A. placenta is the only echinoderm species in the region with which H. placentae associates. Sand dollars are distributed in an aggregated pattern within the littoral zone at Pallarenda Beach, and the distribution of parasites within the adult sand dollar population conforms closely to Poisson expectations. A. placenta adults in all size classes are equally susceptible to parasitization by H. placentae, whereas juveniles are not parasitized host selection may be determined by a requirement for host gonadal tissue in the diet of the parasite. Infestation rate and number of parasites per host decrease as host density increases. Parasite body size is not related to host body size.
Publisher: Elsevier BV
Date: 07-2020
Publisher: Public Library of Science (PLoS)
Date: 19-05-2015
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.
Publisher: Wiley
Date: 04-1994
Publisher: University of Chicago Press
Date: 06-2003
DOI: 10.1086/375177
Abstract: We tested seven hypotheses regarding the mechanisms by which fluctuating asymmetry (FA) originates. We did this by analyzing data on four bilateral characters measured repeatedly during the development of in idual domestic fowl. Immediately posthatching, there was substantial directional asymmetry, which rapidly decreased. We detected FA at significant levels in all characters in the majority of our measurements over the remainder of development. We also examined the effects of known environmental stressors (food and density stress) on levels of FA. At the levels we examined, changes in these stressors did not alter the degree of asymmetry we found in fowl. Time series of asymmetry for in iduals did not exhibit regular oscillations, as much of the relevant literature predicts. Asymmetry levels reflected the combined effects of developmental noise, which was random in degree and direction, and feedback processes, which decreased asymmetry by altering growth rates on both sides of the body. Our findings best fit the predictions of the residual asymmetry and compensatory growth hypotheses, which suggest that levels of asymmetry reflect only recent growth history.
Publisher: Public Library of Science (PLoS)
Date: 18-06-2014
Publisher: Springer Science and Business Media LLC
Date: 1986
DOI: 10.1007/BF00384787
Publisher: Springer Science and Business Media LLC
Date: 12-11-2016
DOI: 10.1007/S00248-015-0701-9
Abstract: Bacterial symbionts on frog skin can reduce the growth of the chytrid fungus Batrachochytrium dendrobatidis (Bd) through production of inhibitory metabolites. Bacteria can be effective at increasing the resistance of hibians to chytridiomycosis when added to hibian skin, and isolates can be screened for production of metabolites that inhibit Bd growth in vitro. However, some bacteria use density-dependent mechanism such as quorum sensing to regulate metabolite production. It is therefore important to consider cell density effects when evaluating bacteria as possible candidates for bioaugmentation. The aim of our study was to evaluate how the density of cutaneous bacteria affects their inhibition of Bd growth in vitro. We s led cutaneous bacteria isolated from three frog species in the tropical rainforests of northern Queensland, Australia, and selected ten isolates that were inhibitory to Bd in standardised pilot trials. We grew each isolate in liquid culture at a range of initial dilutions, sub-s led each dilution at a series of times during the first 48 h of growth and measured spectrophotometric absorbance values, cell counts and Bd-inhibitory activity of cell-free supernatants at each time point. The challenge assay results clearly demonstrated that the inhibitory effects of most isolates were density dependent, with relatively low variation among isolates in the minimum cell density needed to inhibit Bd growth. We suggest the use of minimum cell densities and fast-growing candidate isolates to maximise bioaugmentation efforts.
Publisher: Springer Science and Business Media LLC
Date: 05-2007
DOI: 10.1038/NATURE05940
Abstract: Is global warming contributing to hibian declines and extinctions by promoting outbreaks of the chytrid fungus Batrachochytrium dendrobatidis? Analysing patterns from the American tropics, Pounds et al. envisage a process in which a single warm year triggers die-offs in a particular area (for instance, 1987 in the case of Monteverde, Costa Rica). However, we show here that populations of two frog species in the Australian tropics experienced increasing developmental instability, which is evidence of stress, at least two years before they showed chytrid-related declines. Because the working model of Pounds et al. is incomplete, their test of the climate-linked epidemic hypothesis could be inconclusive.
Publisher: Elsevier
Date: 2015
Publisher: Public Library of Science (PLoS)
Date: 04-12-2013
Publisher: Springer Science and Business Media LLC
Date: 22-01-2020
Publisher: Wiley
Date: 03-10-2014
DOI: 10.1002/ECE3.1271
Publisher: Wiley
Date: 24-10-2007
Publisher: Wiley
Date: 10-08-2017
DOI: 10.1111/COBI.12950
Abstract: Bayesian network analyses can be used to interactively change the strength of effect of variables in a model to explore complex relationships in new ways. In doing so, they allow one to identify influential nodes that are not well studied empirically so that future research can be prioritized. We identified relationships in host and pathogen biology to examine disease-driven declines of hibians associated with hibian chytrid fungus (Batrachochytrium dendrobatidis). We constructed a Bayesian network consisting of behavioral, genetic, physiological, and environmental variables that influence disease and used them to predict host population trends. We varied the impacts of specific variables in the model to reveal factors with the most influence on host population trend. The behavior of the nodes (the way in which the variables probabilistically responded to changes in states of the parents, which are the nodes or variables that directly influenced them in the graphical model) was consistent with published results. The frog population had a 49% probability of decline when all states were set at their original values, and this probability increased when body temperatures were cold, the immune system was not suppressing infection, and the ambient environment was conducive to growth of B. dendrobatidis. These findings suggest the construction of our model reflected the complex relationships characteristic of host-pathogen interactions. Changes to climatic variables alone did not strongly influence the probability of population decline, which suggests that climate interacts with other factors such as the capacity of the frog immune system to suppress disease. Changes to the adaptive immune system and disease reservoirs had a large effect on the population trend, but there was little empirical information available for model construction. Our model inputs can be used as a base to examine other systems, and our results show that such analyses are useful tools for reviewing existing literature, identifying links poorly supported by evidence, and understanding complexities in emerging infectious-disease systems.
Publisher: Inter-Research Science Center
Date: 10-09-2018
DOI: 10.3354/DAO03269
Abstract: Identifying the factors that affect pathogen prevalence is critical to understanding the effects of wildlife diseases. We aimed to examine drivers of seasonal changes in the prevalence of infection by the hibian chytrid fungus Batrachochytrium dendrobatidis in tadpoles. Because tadpoles may be important reservoirs for this disease, examining them will aid in understanding how chytridiomycosis affects entire hibian populations. We hypothesized that temperature is a strong driver of prevalence of Bd in tadpoles, and the accumulation of infection as tadpoles become larger and older also drives prevalence in this system. We studied Litoria rheocola, a tropical rainforest stream frog with seasonal recruitment of annual tadpoles, and surveyed 6 streams in northeastern Queensland, Australia. Comparisons among models relating infection status to stream type, season, their interaction, tadpole age, and water temperature showed that age explained a large portion of the variance in infection status. Across sites and seasons, larger, older tadpoles had increased mean probabilities of infection, indicating that a large component of the variation among in iduals was related to age, and thus to cumulative infection risk. Our results indicate that in systems with annual tadpoles, seasonal changes in infection prevalence may be strongly affected by seasonal patterns of tadpole growth and development in addition to stream type, season, and water temperature. These effects may then influence prevalence of infection in terrestrial in iduals in species that have relatively frequent contact with water. This reinforces the need to integrate studies of the drivers of pathogen prevalence across all host life history stages.
Publisher: The Royal Society
Date: 19-09-2006
Abstract: We investigated the relationship between diet specialization and geographical range in Cophixalus , a genus of microhylid frogs from the Wet Tropics of northern Queensland, Australia. The geographical ranges of these species vary from a few square kilometres in species restricted to a single mountain top to the entire region for the widespread species. Although macroecological theory predicts that species with broad niches should have the largest geographical ranges, we found the opposite: geographically rare species were diet generalists and widespread species were diet specialists. We argue that this pattern is a product of extinction filtering, whereby geographically rare and therefore extinction-prone species are more likely to persist if they are diet generalists.
Publisher: Wiley
Date: 07-2022
DOI: 10.1002/ECS2.4037
Abstract: Emerging infectious diseases are a serious threat to wildlife populations, and there is growing evidence that host microbiomes play important roles in infection dynamics, possibly even mitigating diseases. Nevertheless, most research on this topic has focused only on bacterial microbiomes, while fungal microbiomes have been largely neglected. To help fill this gap in our knowledge, we examined both the bacterial and fungal microbiomes of four sympatric Australian frog species, which had different population‐level responses to the emergence of chytridiomycosis, a widespread disease caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) . We sequenced 16,884 fungal licon sequence variants (ASVs) and 41,774 bacterial ASVs. Bacterial communities had higher richness and were less variable within frog species than were fungal communities. Nevertheless, both communities were correlated for both ASV richness and beta ersity (i.e., frogs with similar bacterial richness and community composition tended to also have similar fungal richness and community composition). This suggests that either one microbial community was having a large impact on the other or that they were both being driven by similar environmental factors. For both microbial taxa, we found little evidence of associations between Bd (prevalence or intensity) and either in iduals' ASVs or beta ersity. However, there was mixed evidence of associations between richness (both bacterial and fungal) and Bd , with high richness potentially providing a protective effect. Surprisingly, the relative abundance of bacteria that have previously been shown to inhibit Bd was also positively associated with Bd infection intensity, suggesting that a high relative abundance of those bacteria provides poor protection against infection.
Publisher: Informa UK Limited
Date: 07-07-2015
No related grants have been discovered for Ross Alford.