Columbia Spotted Frog Rana Luteiventris Research Articles

Genomic signatures of thermal adaptation are associated with clinal shifts of life history in a broadly distributed frog.

Temperature is a critical driver of ectotherm life‐history strategies, whereby a warmer environment is associated with increased growth, reduced longevity and accelerated senescence. Increasing evidence indicates that thermal adaptation may underlie such life‐history shifts in wild populations. Single nucleotide polymorphisms (SNPs) and copy number variants (CNVs) can help uncover the molecular mechanisms of temperature‐driven variation in growth, longevity and senescence. However, our understanding of these mechanisms is still limited, which reduces our ability to predict the response of non‐model ectotherms to global temperature change.In this study, we examined the potential role of thermal adaptation in clinal shifts of life‐history traits (i.e. life span, senescence rate and recruitment) in the Columbia spotted frog Rana luteiventris along a broad temperature gradient in the western United States.We took advantage of extensive capture–recapture datasets of 20,033 marked individuals from eight populations surveyed annually for 14–18 years to examine how mean annual temperature and precipitation influenced demographic parameters (i.e. adult survival, life span, senescence rate, recruitment and population growth). After showing that temperature was the main climatic predictor influencing demography, we used RAD‐seq data (50,829 SNPs and 6,599 putative CNVs) generated for 352 individuals from 31 breeding sites to identify the genomic signatures of thermal adaptation.Our results showed that temperature was negatively associated with annual adult survival and reproductive life span and positively associated with senescence rate. By contrast, recruitment increased with temperature, promoting the long‐term viability of most populations. These temperature‐dependent demographic changes were associated with strong genomic signatures of thermal adaptation. We identified 148 SNP candidates associated with temperature including three SNPs located within protein‐coding genes regulating resistance to cold and hypoxia, immunity and reproduction in ranids. We also identified 39 CNV candidates (including within 38 transposable elements) for which normalized read depth was associated with temperature.Our study indicates that both SNPs and structural variants are associated with temperature and could eventually be found to play a functional role in clinal shifts in senescence rate and life‐history strategies in R. luteiventris. These results highlight the potential role of different sources of molecular variation in the response of ectotherms to environmental temperature variation in the context of global warming.

Amphibian chytrid prevalence on boreal toads in SE Alaska and NW British Columbia: tests of habitat, life stages, and temporal trends.

Tracking and understanding variation in pathogens such as Batrachochytrium dendrobatidis (Bd), the agent of amphibian chytridiomycosis which has caused population declines globally, is a priority for many land managers. However, relatively little sampling of amphibian communities has occurred at high latitudes. We used skin swabs collected during 2005-2017 from boreal toads Anaxyrus boreas (n = 248), in southeast Alaska (USA; primarily in and near Klondike Gold Rush National Historical Park [KLGO]) and northwest British Columbia (Canada) to determine how Bd prevalence varied across life stages, habitat characteristics, local species richness, and time. Across all years, Bd prevalence peaked in June and was >3 times greater for adult toads (37.5%) vs. juveniles and metamorphs (11.2%). Bd prevalence for toads in the KLGO area, where other amphibian species are rare or absent, was highest from river habitats (55.0%), followed by human-modified upland wetlands (32.3%) and natural upland wetlands (12.7%)-the same rank-order these habitats are used for toad breeding. None of the 12 Columbia spotted frogs Rana luteiventris or 2 wood frogs R. sylvatica from the study area tested Bd-positive, although all were from an area of low host density where Bd has not been detected. Prevalence of Bd on toads in the KLGO area decreased during 2005-2015. This trend from a largely single-species system may be encouraging or concerning, depending on how Bd is affecting vital rates, and emphasizes the need to understand effects of pathogens before translating disease prevalence into management actions.

Toxicity of the Piscicide Rotenone to Columbia Spotted Frog and Boreal Toad Tadpoles

AbstractThe piscicide rotenone is commonly used to remove nonnative fishes from natural aquatic systems. While the effects of rotenone on fish are well documented, the effects of this chemical on amphibians are less well known. We determined the toxicity of the rotenone formulation CFT Legumine (5% rotenone) to three ages—Gosner age ranges 21–25, 30–35, and 40–45—of tadpoles of the Columbia spotted frog Rana luteiventris and the boreal toad Anaxyrus boreas under laboratory conditions. Tadpoles of both species were exposed to 0.1, 0.5, and 1.0 mg/L CFT Legumine (0.005, 0.025, and 0.050 mg/L rotenone, respectively) in static, 96‐h exposure trials; surviving individuals were placed in rotenone‐free water and raised until metamorphosis. In an additional experiment, Columbia spotted frog tadpoles were exposed to 1.0 mg/L CFT Legumine for 1, 2, 3, or 4 h before being placed in rotenone‐free water for the duration of a 96‐h exposure period. Tadpole mortality increased with increases in CFT Legumine concentration and exposure period. Individuals exposed to 1.0 mg/L of product experienced significantly greater mortality than did control tadpoles (P < 0.001), with 99–100% mortality occurring in the youngest age‐group (Gosner 21–25) in both species. In Columbia spotted frog tadpoles, mortality decreased as age increased, while age did not affect mortality in boreal toad tadpoles. Rotenone produced no biologically significant effects on growth or metamorphosis. Our findings suggest that the use of 1.0 mg/L CFT Legumine to remove nonnative fish may cause significant mortality to larval amphibians if they are exposed for 96 h; exposures to lower dosages (0.5 mg/L of product) or for shorter durations (≤4 h), however, resulted in less mortality. Fisheries managers can use these results to improve amphibian conservation in fish restoration areas and reduce the impacts on larval amphibian populations.

Batrachochytrium dendrobatidis infection dynamics in the Columbia spotted frog Rana luteiventris in north Idaho, USA

The pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd) is contributing to amphibian declines worldwide. Temperature plays an important role in both pathogen growth and host immune function, but little is known about seasonal dynamics of Bd infection in north temperate regions. Our objective was to increase understanding of Bd disease ecology by investigating patterns of Bd infection of Columbia spotted frogs Rana luteiventris across seasons, age classes, and sexes in north Idaho, USA. We collected skin swabs from 223 R. luteiventris in spring, summer, and fall 2009 at 7 ponds in the Palouse region and quantified Bd zoospores for each sample using quantitative PCR. Across seasons, Bd prevalence of adults was higher in summer than in spring or fall, suggesting that individuals may be clearing low-level infections over the summer. Among age classes, all but one late stage tadpole (Gosner stage 43-45) tested negative for Bd. Conversely, 100% of metamorphs tested positive for Bd and had the highest Bd loads of all age classes, suggesting they may be the most vulnerable age class. Adult R. luteiventris had high infection prevalence (> 60%) in all seasons, indicating that Bd infection is maintained within populations and that adults likely serve as disease reservoirs across seasons. Among adults, we also found weak evidence for females having higher infection prevalence than males. Further laboratory and field studies are needed to determine whether there are individual and population impacts from Bd on R. luteiventris and other amphibians in north Idaho.