Linking biogeography and evolution: environmental variation and evolutionary dynamics of phenotypes in wild bird populations
Natural selection is the main mechanism and most powerful explanation for adaptive evolution, and environmental variation is the main fuel that feeds the engine of natural selection. From a microevolutionary perspective, evolution can be detected within populations where natural selection acts on the expression of phenotypes. We are starting to unravel how and what agents of selection can cause evolutionary adaptation within a temporal perspective. However, our knowledge is rather limited towards very few species that are experiencing particular environmental conditions. In addition, and unsurprisingly, biogeographically dispersed populations of the same species can respond differently to the same agent of selection, i.e. climate change is expected to have different evolutionary responses depending on the environmental conditions that every population experiences. Here we illustrate how evolutionary dynamics of phenotypes and biogeography can be married using species distribution models built with
the favourabilityfunction. We use own and bibliographic-based data gathering more than 1400 estimates of evolutionary traits in wild European populations of birds. We found that selection gradients increase as environmental favourability increases for secondary sexual traits in pied flycatchers (Ficedula hypoleuca). At multispecies level, we also found that both evolvability and selection gradients of multiple phenotypes are linked to environmental favourability in a non-linear way: selection and evolvability decreases at both ends of environmental favourability. We suggest how intra- and inter-specific interactions within populations might explain these patterns. More importantly, we present a new methodological approach to link both fields of research and discuss its limitations and benefits.