Chytrid infection dynamics in frog populations from climatically disparate regions

Turner, Anna; Wassens, Skye; Heard, Geoffrey W.

doi:10.1016/j.biocon.2021.109391

Cited by 7 publications

(10 citation statements)

References 49 publications

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“…The skew of the age structure was more pronounced in the semi‐arid region, with 92% of those sampled being young of year (Figure 2b ). In line with the effects of Bd on age structure in the congener Litoria verreauxii alpina (Scheele et al, 2016 ), we expected a greater skewing of age structure in the temperate region due to higher prevalence of Bd (Turner, Wassens, & Heard, 2021 ) and the continuing effect of Bd on survival rates of L. raniformis (Heard et al, 2014 ). However, this was not observed.…”

Section: Discussionsupporting

confidence: 56%

“…In a previous study (Turner, Wassens, & Heard, 2021 ), we showed that the prevalence and intensity of Bd infections among L. raniformis differs markedly between semi‐arid and temperate portions of the range of L. raniformis . In the semi‐arid zone in which maximum temperatures during the active season are 4.5°C higher on average and rainfall is 50% lower, observed seasonal Bd prevalence is 8% compared with 23% in the temperate region.…”

Section: Introductionmentioning

confidence: 69%

“…Percentage emergent vegetation in the survey transect was visually assessed according to Sainty and Jacobs ( 2003 ). Water chemistry parameters (temperature [°C], pH, conductivity [mScm −1 ]) were measured using hand‐held meters (Horiba U‐52 Multiparameter meter, Horiba, Ltd. Kyoto, Kyoto, Japan or Oakton CON11 water quality meter, Oakton Instruments, Vernon Hills, Illinois, USA).Temperature loggers deployed at each site were used to calculate average seasonal air and water temperatures along with proportion of air and water temperatures within the chytrid thermal optimum (17–26°C) (Turner, Wassens, & Heard, 2021 ).…”

Section: Methodsmentioning

confidence: 99%

“…A negative linear relationship was detected between salinity and chytrid prevalence in Turner, Wassens, and Heard ( 2021 ) as Bd is intolerant of saline conditions. Therefore, increasing salinity will decrease prevalence of infections.…”

Section: Methodsmentioning

confidence: 99%

“…Nineteen candidate models were developed in total (Table S1 ), guided by: (1) temperature, pH, and salinity as drivers of Bd infection prevalence and intensity identified in Turner, Wassens, and Heard ( 2021 ) and (2) other potential drivers of survival and age of amphibians such as hydroperiod and aquatic vegetation (Wassens et al, 2010 ). Despite predicted effect of sex on survival rate and therefore age structures, sex was not included in the model set as it was unknown for immature individuals.…”

Section: Methodsmentioning

confidence: 99%

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Age structure of amphibian populations with endemic chytridiomycosis, across climatic regions with markedly different infection risk

Turner

Heard

Hall

et al. 2022

Ecology and Evolution

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Threatening processes, such as disease, can drive major changes in population demographics of the host. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd ), has led to the decline of at least 500 amphibian species across the globe and has been shown to truncate host age structure by lowering adult survival rates. This results in heavy reliance on annual recruitment and the inability to recover in the event of periodic recruitment failure. We used skeletochronology to determine the age structure, growth, and survival rates of populations of an endangered amphibian, Litoria raniformis , with endemic chytridiomycosis, across two climatically disparate regions in south‐eastern Australia: semi‐arid and temperate. Contrary to predictions, populations in the semi‐arid region (in which chytrid prevalence is substantially lower due to high temperatures) displayed a more truncated age structure than populations in the temperate study regions. Maximum recorded age was only two years in the semi‐arid region compared with up to four years in the temperate region. Wetland hydroperiod and average seasonal air temperature were correlated with age, and males had a slightly higher survival rate than females (0.31 for males and 0.27 for females). Despite the previously documented differences in chytrid prevalence between the two climatic regions, water availability and wetland hydroperiods appear the over‐riding determinants of the age structure and survival rates of L. raniformis . Targeted management which ensures water availability and improves survival of 1‐year‐old frogs into their second and third breeding season would reduce the impact of stochastic events on L. raniformis , and this may be true for numerous frog species susceptible to chytridiomycosis.

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Section: Discussionsupporting

confidence: 56%

Section: Introductionmentioning

confidence: 69%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Age structure of amphibian populations with endemic chytridiomycosis, across climatic regions with markedly different infection risk

Turner

Heard

Hall

et al. 2022

Ecology and Evolution

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Stochastic metapopulation dynamics of a threatened amphibian to improve water delivery

Mathwin,

Wassens,

Gibbs

et al. 2024

Ecosphere

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Water extraction and climate change are altering the availability of surface water globally, thereby contributing to amphibian population declines. The managed delivery of water to benefit environmental values (environmental watering) is a promising conservation technique that can support amphibian recruitment and maintain viable populations. Environmental water can be delivered in various spatial patterns and with different frequencies, but comparing the effectiveness of competing strategies is complicated by variable and interactive environmental processes. We built a spatially explicit, stochastic, hydroecological metapopulation model to compare the effects of five environmental‐watering scenarios on the probability of persistence of threatened southern bell frogs (Litoria raniformis) in a major river reach in southern Australia. We compared a no‐intervention control to two managed watering frequencies (moderate and frequent) delivered in two spatial designs (managed wetlands grouped or spread across the reach). More frequent water provision to intervention sites improved the reach‐wide (metapopulation) probability of persistence, and spreading intervention sites across the reach improved persistence more than grouping intervention sites together. When re‐examined under severe drought conditions, L. raniformis had a 0.04 probability of persistence without intervention, which improved to 0.56 with high watering frequency. Model‐guided environmental water provision can improve reach‐wide persistence of amphibian metapopulations by guiding spatial and temporal delivery patterns to reduce the risk of extinction.

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The effect of salt dosing for chytrid mitigation on tadpoles of a threatened frog, Litoria aurea

et al. 2023

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The novel fungal pathogen Batrachochytrium dendrobatidis (chytrid) is one of the greatest threats to amphibians worldwide. Small increases in water salinity (up to ca. 4 ppt) have been shown to limit chytrid transmission between frogs, potentially providing a way to create environmental refugia to reduce its impact at a landscape scale. However, the effect of increasing water salinity on tadpoles, a life stage confined to water, is highly variable. Increased water salinity can lead to reduced size and altered growth patterns in some species, with flow-on effects to vital rates such as survival and reproduction. It is thus important to assess potential trade-offs caused by increasing salinity as a tool to mitigate chytrid in susceptible frogs. We conducted laboratory experiments to examine the effects of salinity on the survival and development of tadpoles of a threatened frog (Litoria aurea), previously demonstrated as a suitable candidate for trialling landscape manipulations to mitigate chytrid. We exposed tadpoles to salinity ranging from 1 to 6 ppt and measured survival, time to metamorphosis, body mass and locomotor performance of post-metamorphic frogs as a measure of fitness. Survival and time to metamorphosis did not differ between salinity treatments or controls reared in rainwater. Body mass was positively associated with increasing salinity in the first 14 days. Juvenile frogs from three salinity treatments also showed the same or better locomotor performance compared to rainwater controls, confirming that environmental salinity may influence life history traits in the larval stage, potentially as a hormetic response. Our research suggests that salt concentrations in the range previously shown to improve survival of frogs in the presence of chytrid are unlikely to impact larval development of our candidate threatened species. Our study lends support to the idea of manipulating salinity to create environmental refugia from chytrid for at least some salt-tolerant species.

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Chytrid infection dynamics in frog populations from climatically disparate regions

Cited by 7 publications

References 49 publications

Age structure of amphibian populations with endemic chytridiomycosis, across climatic regions with markedly different infection risk

Age structure of amphibian populations with endemic chytridiomycosis, across climatic regions with markedly different infection risk

Stochastic metapopulation dynamics of a threatened amphibian to improve water delivery

The effect of salt dosing for chytrid mitigation on tadpoles of a threatened frog, Litoria aurea

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