Predicting climate change adaptive potential in red-backed salamanders: Within-population variation in responses to climate
The red-backed salamander (RBS; Plethodon cinereus) presents a unique system to understand potential climate adaptation for amphibian species. RBS populations have two sympatric color morphs (striped, unstriped) that commonly co-occur but appear to have different environmental tolerances as evidenced by physiological, behavioral, and distributional studies. This “climate-morph hypothesis” (CMH) suggests that this polymorphism is a sufficient indicator of within-population genetic variation in respect to climate. Considering no studies have examined the CMH at the population level while accounting for seasonal or annual variation, we tested predictions from the CMH using four years of RBS capture mark-recapture data from Maryland in order to understand RBS adaptive capacity. We tested multiple predictions relating to behavioral plasticity (surface and sub-surface use/movement) and demography (survival, individual growth) using a variety of analytical techniques: robust design population models, hierarchical spatial capture-recapture models, and mixed-effects von Bertalanffy growth models.
Data came from three cover board arrays and included 2,805 captures over 8 seasons. From this, we provide the first ever estimates of RBS survival (lowest in summer 2010, Φ = 0.571, 95%CI [0.435, 0.657]; highest in winter 2009, Φ = 0.862, 95% CI [0.643, 0.956]). For both morphs there are consistently lower oversummer survival rates as compared to overwinter survival rates in the same year. While all RBS showed some seasonal variation in behavior and demography, on all accounts there were no significant differences between color morph timing on surface, morph relationships with rainfall or temperature, breadth of surface movement, survival, or growth. This provides strong evidence that the CMH does not hold true for this population, and it adds to the growing body of literature that RBS color morphs are not an appropriate proxy for within-population genetic variation. Therefore, color morph cannot be used to predict adaptive capacity as others have suggested.