ROberta Bisconti, Andrea Chiocchio , David Costantini, Claudio Carere, Daniele Canestrelli

Addressing how individual variation within populations drives the evolution of biodiversity patterns is a major challenge in ecology and evolutionary biology. Historical biogeographic processes have had dramatic consequences on the structure of biodiversity. However, while the interplay between historical processes and genotypic diversity within populations has been widely investigated, the effects of such processes on phenotypic diversity remain poorly explored. Here, we investigate whether dispersal-driven processes of historical biogeographic relevance, such as late Pleistocene range dynamics, have contributed to shape the geographic patterns of phenotypic trait variation. We focus on dispersal-related personality, morphological and performance traits in the Tyrrhenian tree frog, Hyla sarda, which underwent a northward range expansion from the Sardinia Island to the Corsica Island during the Last Glacial Maximum, when a temporary land-bridge connected these islands. We collected tree frogs from four geographic areas along the past expansion route, controlling for altitude, local habitat, demographic factors, and bioclimatic differences between geographic areas. Then, we scored intraspecific variation in two personality traits, two performance traits, along with morphological traits likely involved in the dispersal process. Tree frogs from the northern area in Corsica were more prudent in a novel environment, they had significantly larger body size, longer limbs, wider heads, and displayed stronger take-off and adhesion performances compared to individuals from the source area in Sardinia. Overall, these results suggest a non-random spatial sorting of the intraspecific variation in multiple phenotypic traits during the range expansion phase. In turn, they also suggest that population differentiation in phenotypic traits associations might be a legacy of past biogeographic dynamics, identifying an overlooked driver of the current phenotypic architecture of animal populations.