Natural selection on plasticity of thermal traits in a highly seasonal environment

Abstract

For ectothermic species with broad geographical distributions, latitudinal/altitudinal variation in environmental temperatures (averages and extremes) is expected to shape the evolution of physiological tolerances and the acclimation capacity (i.e., degree of phenotypic plasticity) of natural populations. This can create geographical gradients of selection in which environments with greater thermal variability (e.g., seasonality) tend to favor individuals that maximize performance across a broader range of temperatures compared to more stable environments. Although thermal acclimation capacity plays a fundamental role in this context, it is unknown whether natural selection targets this trait in natural populations. Additionally, understanding whether and how selection acts on thermal physiological plasticity is also highly relevant to climate change and biological conservation. Here, we addressed such an important gap in our knowledge in the northernmost population of the four‐eyed frog, Pleurodema thaul. We measured plastic responses of critical thermal limits for activity, behavioral thermal preference, and thermal sensitivity of metabolism to acclimation at 10 and 20°C. We monitored survival during three separate recapture efforts and used mark‐recapture integrated into an information‐theoretic approach to evaluate the relationship between survivals as a function of the plasticity of thermal traits. Overall, we found no evidence that thermal acclimation in this population is being targeted by directional selection, although there might be signals of selection on individual traits. According to the most supported models, survival increased in individuals with higher tolerance to cold when cold‐acclimated, probably because daily low extremes are frequent during the cooler periods of the year. Furthermore, survival increased with body size. However, in both cases, the directional selection estimates were nonsignificant, and the constraints of our experimental design prevented us from evaluating more complex models (i.e., nonlinear selection).

Thermal adaptation revisited: How conserved are thermal traits of reptiles and amphibians?

“…Although direct evidence for heritability in thermal traits remains scant, evidence for selection on thermal traits is robust. In four‐eyed frogs ( Pleurodema thaul ), individuals with greater CT min exhibited higher survivorship when cold‐acclimated, though little evidence was found for selection on several other thermal traits (Bacigalupe et al, 2018). In Zootoca vivipara , under seminatural conditions, there was evidence of stabilizing selection on preferred body temperature, but little evidence for correlated selection on the thermal sensitivity of sprint performance, thermoregulatory behavior, and resting metabolic rate (Artacho et al, 2015).…”

Ecological mechanism of climate‐mediated selection in a rapidly evolving invasive species

“…2017; Bacigalupe et al . 2018). In many arthropods, a crucial ecological adaptation is autumnal photoperiodic diapause (Tauber et al .…”

Rapid adaptation of the Irish potato famine pathogen Phytophthora infestans to changing temperature

“…The two adaptation processes are interconnected to provide an opportunity for the organism in question to survive, reproduce, and compete in new environments (Willmott et al, 2018). Many empirical studies of thermal adaptation have focused on the scales and patterns of physiological adaptation, that is, phenotypic plasticity (Bacigalupe et al, 2018;Chown, Addo-Bediako, & Gaston, 2002;Garrett et al, 2006;Willmott et al, 2018). In contrast, evolutionary inferences on how fast genetic adaptation can occur and how such adaptations may affect biological interactions among traits are relatively limited, particularly in plant pathogens.…”