Ecological divergence among young lineages favours sympatry, but convergence among old ones allows coexistence in syntopy

Abstract

Aim We analyse when and why closely related species start to coexist in sympatry at the range (continental) scale, and in syntopy at the local (community) scale. We contrast the idea that limiting similarity and time constrain the transition to sympatry of sister lineages after their initial allopatric split, with the hypothesis of ecological convergence, leading to the coexistence of species with similar ecological attributes in similar environments. Location European continent, north‐west Italy and north‐west Spain. Methods With a comparative framework we test whether the spatial overlap of bird ranges within Europe, at the continental scale, and in two European regions at the community scale, vary with their degree of ecological similarity (trophic niche, body size, elevational preferences), when accounting for the evolutionary time available for range expansion. Results A larger number of sister species with recent common ancestors are found in the continent than within communities, a likely consequence of the allopatric mode of divergence of lineages. Divergence in elevational preferences and niche breadth favoured a way back to secondary sympatry of European sister species, which took place c . 2 Myr after their split. Once in sympatry, the coexistence of species at the local scale took almost twice as long and was instead favoured by ecological convergence. Main conclusions Ecological similarity poses a fundamental constraint to species coexistence, but whether it hamp…