Locally-adapted reproductive photoperiodism determines population vulnerability to climate change in burying beetles

Assessing species vulnerability to anthropogenic climate change is critical for conserving global biodiversity. Most current methods for predicting how species will respond to climate change depend to a large extent on species distribution models that relate environmental variables to the distribution of species and predict habitat suitability under climate change scenarios using species-specific functional traits. However, since populations and not species adapt to changing environmental conditions, determining the mechanisms underlying intraspecific differences in functional trait values is crucial for assessing species vulnerability to climate change.

Yet, little is known about the key functional traits that determine the distribution of populations and the main mechanisms—phenotypic plasticity vs. local adaptation—underlying intraspecific functional trait variation. Using the Asian burying beetle Nicrophorus nepalensis, Hsiang-Yu Tsai et al., demonstrate that mountain ranges differing in elevation and latitude offer unique thermal environments in which two functional traits—thermal tolerance and reproductive photoperiodism—interact to shape breeding phenology. They show that populations on different mountain ranges maintain similar thermal tolerances, but differ in reproductive photoperiodism. Through common garden and reciprocal transplant experiments, the study confirms that reproductive photoperiodism is locally adapted and not phenotypically plastic. Accordingly, year-round breeding populations on mountains of intermediate elevation are likely to be most susceptible to future warming because maladaptation occurs when beetles try to breed at warmer temperatures.