Intra‐generic species richness and dispersal ability interact to determine geographic ranges of birds

Abstract

Abstract Aim Understanding the factors that influence the geographic ranges of species remains a challenge in ecology and evolutionary biology. In particular, little consensus exists as to whether geographic ranges of species are determined by biotic interactions such as inter‐specific competition. We evaluated how intra‐generic species richness, which could act as a surrogate for biotic interactions, dispersal ability, taxon age and habitat shift since the L ast G lacial M aximum influenced the extent to which species in the bird genus S ylvia (Old World typical warblers) occur in all areas predicted to be environmentally suitable (i.e. range filling). Location P alaearctic, A frotropics and I ndo‐ M alaya. Methods We quantified range filling in the bird genus S ylvia using boosted regression trees and ridge regression. We tested for effects of intra‐generic species richness, dispersal ability, taxon age and habitat shift since the L ast G lacial M aximum on range filling using multiple regression. To evaluate different hypotheses about how local‐scale competition might influence large‐scale range dynamics we explore patterns of intra‐generic species richness in habitats of varying suitability. Results S ylvia warblers with higher dispersal ability showed higher range filling, but only if congeneric species richness in less suitable habitats within their potential range was low. Taxon age and habitat shift since the L ast G lacial M aximum had no consistent effect. Main conclusions We show that S ylvia ranges are shaped by the simultaneous, interactive effect of both congeneric species richness and dispersal ability. We suggest that this interaction could reflect a potential effect of competition on range filling. If biotic interactions generally influence the ability of species to colonize and occupy habitat at the continental scale, predicting the impact of climate change on biodiversity will be challenging.