Home and away: allometry and climate drive morphology of European rabbits in their native and introduced range

Climatic conditions shape phenotypic evolution by driving adaptations that optimise organismal function. Invasive species provide valuable systems to study these processes, as they often encounter novel climatic conditions in their introduced ranges. The European rabbit Oryctolagus cuniculus , native to the Iberian Peninsula, has established populations across Europe and Australia, where climatic conditions differ markedly. We examined how temperature, aridity, and precipitation jointly influence cranial morphology across native and invasive populations. Australia is generally warmer and more arid than European locations and we found that rabbits from Australia exhibited larger overall body size. Climate appears to shape morphological diversity differently in introduced versus native ranges by leveraging changes to trait allometry. Climate alone was found to be not as influential on rabbit morphology in the introduced range as it is in Europe. These findings demonstrate that a mosaic effect of different climatic factors shapes morphological evolution, particularly for invasive species adapting to novel ecological conditions. Furthermore, we suggest that allometry could potentially act as a mechanism to generate change in individual traits when animals are introduced to novel habitats, although the factors responsible for driving body size in rabbits of Australia remain to be understood.