Thermal niche variation among individuals of the poison frog, Oophaga pumilio, in forest and converted habitats

The conversion of natural habitats to human land uses often increases local temperatures, creating novel thermal environments for species. The variable responses of ectotherms to habitat conversion, where some species decline while others persist, can partly be explained by variation among species in their thermal niches. However, few studies have examined thermal niche variation within species and across forest‐land use ecotones, information that could provide clues about the capacity of species to adapt to changing temperatures. Here, we quantify individual‐level variation in thermal traits of the tropical poison frog, Oophaga pumilio, in thermally contrasting habitats. Specifically, we examined local environmental temperatures, field body temperatures (Tb), preferred body temperatures (Tₚᵣₑf), critical thermal maxima (CTₘₐₓ), and thermal safety margins (TSM) of individuals from warm, converted habitats and cool forests. We found that frogs from converted habitats exhibited greater mean Tb and Tₚᵣₑf than those from forests. In contrast, CTₘₐₓ and TSM did not differ significantly between habitats. However, CTₘₐₓ did increase moderately with increasing Tb, suggesting that changes in CTₘₐₓ may be driven by microscale temperature exposure within habitats rather than by mean habitat conditions. Although O. pumilio exhibited moderate divergence in Tₚᵣₑf, CTₘₐₓ appears to be less labile between habitats, possibly due to the ability of frogs in converted habitats to maintain their Tb below air temperatures that reach or exceed CTₘₐₓ. Selective pressures on thermal tolerances may increase, however, with the loss of buffering microhabitats and increased frequency of extreme temperatures expected under future habitat degradation and climate warming. Abstract in Spanish is available with online material.