Eco-evolutionary responses of species distributions to climate change

Species elevational shifts are well-documented responses to climate change, with many moving upslope to track suitable conditions. However, these shifts can vary considerably in both direction and rate, and the underlying causes of this variability are not well understood. This study examines how elevational shifts depend on geographical zones along with species' climatic niches, global prevalence, and evolutionary history by analyzing paired lower and upper edge shifts across 845 plant and animal species records worldwide. We find distinct effects of these drivers on upper versus lower distribution limits. Tropical species experienced more rapid upward shifts of their lower edges than did temperate species. Species with warmer and wetter optimal climatic niches displayed faster upper-edge shifts, while those only with wetter ones showed more rapid lower-edge shifts. Globally prevalent species expanded their distributions with climate change by combining faster upper-edge advances with slower lower-edge contractions, likely reflecting their drier climatic adaptation. Importantly, these ecological effects overlapped substantially with phylogenetic effects, and phylogenetic conservatism independently explained a notable portion of the variation in elevational responses. These findings highlight the complexity of evolutionary history and ecological processes in shaping species' climate responses and underscore the climate vulnerability of some species due to their evolutionary inertia.