Natural disturbance reduces disease risk in endangered rainforest frog populations

Roznik, Elizabeth A.; Sapsford, Sarah J.; Pike, David A.; Schwarzkopf, Lin; Alford, Ross A.

doi:10.1038/srep13472

Cited by 41 publications

(44 citation statements)

References 62 publications

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“…; Roznik et al . ) on amphibian‐Bd dynamics, but few mitigation strategies have been field tested and no single strategy is appropriate for all species threatened by Bd (Converse et al . ; Garner et al .…”

Section: Methodsmentioning

confidence: 99%

Identifying Species Conservation Strategies to Reduce Disease‐Associated Declines

Gerber

Converse

Muths

et al. 2017

CONSERVATION LETTERS

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Emerging infectious diseases (EIDs) are a salient threat to many animal taxa, causing local and global extinctions, altering communities and ecosystem function. The EID chytridiomycosis is a prominent driver of amphibian declines, which is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). To guide conservation policy, we developed a predictive decision-analytic model that combines empirical knowledge of host-pathogen metapopulation dynamics with expert judgment regarding effects of management actions, to select from potential conservation strategies. We apply our approach to a boreal toad (Anaxyrus boreas boreas) and Bd system, identifying optimal strategies that balance tradeoffs in maximizing toad population persistence and landscape-level distribution, while considering costs. The most robust strategy is expected to reduce the decline of toad breeding sites from 53% to 21% over 50 years. Our findings are incorporated into management policy to guide conservation planning. Our online modeling application provides a template for managers of other systems challenged by EIDs.

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Section: Methodsmentioning

confidence: 99%

Identifying Species Conservation Strategies to Reduce Disease‐Associated Declines

Gerber

Converse

Muths

et al. 2017

CONSERVATION LETTERS

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“…), and that natural canopy thinning from storm damage has been shown to increase insolation and reduce Bd infection prevalence for some susceptible stream frogs (Roznik et al . ).…”

Section: Discussionmentioning

confidence: 97%

Can Habitat Management Mitigate Disease Impacts on Threatened Amphibians?

Heard

Scroggie

Ramsey

et al. 2017

CONSERVATION LETTERS

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Chytridiomycosis has decimated amphibian biodiversity. Management options for the disease are currently limited, but habitat manipulation holds promise due to the thermal and physicochemical sensitivities of chytrid fungi. Here, we quantify the extent to which habitat management could reduce metapopulation extinction risk for an Australian frog susceptible to chytridiomycosis. Our modeling revealed that: (1) habitat management is most effective in climates where hosts are already less susceptible to the disease; (2) creating habitat, particularly habitat with refugial properties adverse to the pathogen, may be substantially more effective than manipulating existing habitat; and (3) increasing metapopulation size and connectivity through strategic habitat creation can greatly reduce extinction risk. Controlling chytridiomycosis is a top priority for conserving amphibians. Our study provides impetus for experiments across a range of species and environments to test the capacity of habitat management to mitigate the impacts of this pervasive disease.

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“…Specifically, our results indicate that even in habitats in which average environmental temperatures may be suitable for pathogen growth and reproduction, infection risk or the outcome of an existing infection may be heavily influenced by host behaviours, such as microhabitat selection and thermoregulation, that briefly increase body temperatures to those that are detrimental to the parasite. Thus, management interventions incorporating environmental manipulation could aid in protecting some frog populations from chytridiomycosis‐related declines (Garner et al., ; Roznik et al., ; Scheele et al., ), although variability in the heat tolerance of different Bd strains could limit the applicability of this type of intervention to only some of the regions where Bd occurs. Providing canopy openings that facilitate frog basking, via small‐scale removal of trees or large branches overhanging critical habitat (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…behavioural fever) or to aid metabolism or reproduction (Murphy, St‐Hilaire, & Corn, ; Richards‐Zawacki, ; Rowley & Alford, ). Alternatively, changes in frog body temperature may occur passively or by chance, with natural or anthropogenic fluctuations in the microenvironments of individuals or the macroenvironments of populations (Rowley & Alford, ; Roznik, Sapsford, Pike, Schwarzkopf, & Alford, ). In rainforest ecosystems where environmental conditions are suitable for Bd growth most of the time, these processes may briefly elevate frog body temperatures so that they exceed the thermal optimum of the fungus.…”

Section: Introductionmentioning

confidence: 99%

Realistic heat pulses protect frogs from disease under simulated rainforest frog thermal regimes

et al. 2017

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Recent emergences of fungal diseases have caused catastrophic global losses of biodiversity. Temperature is one of the most important factors influencing host–fungus associations but the effects of temperature variability on disease development are rarely examined. The chytrid pathogen Batrachochytrium dendrobatidis (Bd) has had severe effects on populations of hundreds of rainforest‐endemic amphibian species but we know little about the effects of rainforest‐specific host body temperature cycles on infection patterns. To address this challenge, we used body temperature regimes experienced in nature by frogs in the Australian Wet Tropics to guide a controlled experiment investigating the effects of body temperature fluctuations on infection patterns in a model host (Litoria spenceri), with emphasis on exposing frogs to realistic “heat pulses” that only marginally exceed the thermal optimum of the fungus. We then exposed cultured Bd to an expanded array of heat pulse treatments and measured parameters of population growth to help resolve the role of host immunity in our in vivo results. Infections developed more slowly in frogs exposed to daily 4‐hr heat pulses of 26°C or 29°C than in frogs in constant temperature treatments without heat pulses (control). Frogs that experienced heat pulses were also less likely to exceed infection intensities at which morbidity and mortality become likely. Ten of 11 (91%) frogs from the daily 29°C heat pulse treatment even cleared their infections after approximately 9 weeks. Cultured Bd also grew more slowly when exposed to heat pulses than in constant‐temperature control treatments, suggesting that mild heat pulses have direct negative effects on Bd growth in nature, but precluding us from determining whether there was a concurrent benefit of heat pulses to host immunity. Our results suggest that even in habitats where average temperatures may be suitable for fungal growth and reproduction, infection risk or the outcome of existing infections may be heavily influenced by short but frequent exposures to temperatures that only slightly exceed the optimum for the fungus. Our findings provide support for management interventions that promote warm microenvironments for hosts, such as small‐scale removal of branches overhanging critical habitat or provision of artificial heat sources. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12944/suppinfo is available for this article.

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Natural disturbance reduces disease risk in endangered rainforest frog populations

Cited by 41 publications

References 62 publications

Identifying Species Conservation Strategies to Reduce Disease‐Associated Declines

Identifying Species Conservation Strategies to Reduce Disease‐Associated Declines

Can Habitat Management Mitigate Disease Impacts on Threatened Amphibians?

Realistic heat pulses protect frogs from disease under simulated rainforest frog thermal regimes

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