Patterns of Genetic Variation in Desiccation Tolerance in Embryos of the Terrestrial-Breeding Frog, Pseudophryne Guentheri

Abstract

Environmental change often requires evolutionary responses, and therefore understanding the genetic architecture of susceptible populations is essential for predicting their capacity to respond adaptively. However, quantitative genetic studies are rarely targeted at populations considered vulnerable to such environmental perturbations. Here, we assess the level of heritable variation in the ability of embryos to tolerate desiccation stress in Pseudophryne guentheri, a terrestrial-breeding frog that is currently experiencing a drying climate. We applied a North Carolina II breeding design to identify sources of genetic and environmental variance, and genotype-by-environment interactions (GEIs), underlying the expression of embryo survival, hatching times, hatchling mass, size, and shape. Our analysis revealed highly significant effects of water potential and maternal effects on all measured traits, while additive genetic effects were significant for hatchling shape, and nonadditive effects were observed for embryo survival. Interestingly, GEIs, including for some traits complex three-way sire-by-dam-by-environment interactions, were significant, indicating that progeny from certain male-female crosses were more tolerant to water stress than others. These findings suggest a limited capacity of P. guentheri to respond to a drying climate, but also reveal that the detrimental effects of nonviable male-female crosses (i.e., genetic incompatibility) can be masked in benign environments.

The other 96%: Can neglected sources of fitness variation offer new insights into adaptation to global change?

“…To explore how nonadditive genetic and maternal environmental effects on larval survival may affect Galeolaria 's persistence in variable thermal environments, we estimated covariation in these effects across all environments in which survival was assayed. Encouragingly, we found that nonadditive genetic effects on survival covaried positively across environments, in contrast to recent suggestions that the exposure of unfavorable nonadditive effects by thermal stress (Eads, Mitchell, & Evans, 2012; Lymbery & Evans, 2013) may lead to fitness trade‐offs across stress levels. Here, however, we found no evidence of such trade‐offs.…”

Metabolic and functional characterization of effects of developmental temperature in Drosophila melanogaster

“…Predicting the future distributions of ectotherms in a warmer, but also more variable, environment with more extreme thermal episodes at both ends of the thermal scale can be addressed by studying the ability to adapt through evolutionary, behavioral, or plastic responses (23). A number of recent studies suggest that some species of frogs (17), phytoplankton (24), copepods (27, 28), and insects (22) are evolutionarily constrained when it comes to coping with extreme environments due to, e.g., lack of adaptive genetic variation. Thus current and future species distributions will partly depend on migration, behavioral thermoregulation, and physiological plastic responses; the latter being the focus of this study.…”

A genome‐wide search for local adaptation in a terrestrial‐breeding frog reveals vulnerability to climate change

“…Rainfall is an important trigger of breeding, it initiates hatching and provides the ephemeral water sources that allow the completion of metamorphosis (Bradford & Seymour, 1988). In concert, these variables potentially create intense selection, likely influencing embryonic mortality, the time taken to hatch (induced when nest sites flood), the rate of larval development and the survival of metamorphs Donnelly & Crump, 1998;Eads et al, 2012). In concert, these variables potentially create intense selection, likely influencing embryonic mortality, the time taken to hatch (induced when nest sites flood), the rate of larval development and the survival of metamorphs Donnelly & Crump, 1998;Eads et al, 2012).…”

“…An overall decrease in rainfall, plus increasing variation in precipitation, such as the incidence and severity of drought events, will likely have a severe negative effect on both aquatic and terrestrial-breeding anurans as breeding success, phenology and migration are tightly associated with the presence of water (Todd & Winne, 2006;Walls, Barichivich, & Brown, 2013). For example, frogs in the Australian Pseudophryne genus lay their eggs in burrows in direct contact with the soil, and rainfall keeps embryos hydrated and ultimately floods the burrows (Eads, Mitchell, & Evans, 2012). For example, frogs in the Australian Pseudophryne genus lay their eggs in burrows in direct contact with the soil, and rainfall keeps embryos hydrated and ultimately floods the burrows (Eads, Mitchell, & Evans, 2012).…”

“…These include genes involved in the hatching response (for which there is evidence of heritability in this species;Eads et al, 2012), and genes that influence larval development rates. Hence, northern populations may be locally adapted to express PKC zeta at higher levels for faster oocyte maturation to exploit unpredictable rainfall events for breeding.…”