Emergence of sympatry in a radiation of subterranean amphipods

Abstract

Abstract Aim We tested the hypothesis that sympatry among closely related species is possible only in the absence of interspecific competition. Location Dinaric Karst, Western Balkan, Europe. Taxon A clade of subterranean amphipods, genus Niphargus (Crustacea: Amphipoda). Methods Phylogenetic reconstructions; species delimitation; modelling competition using phylogeny and species distributions; reconstruction of historical dispersal. Results The clade comprises six species, which classify into two ecomorphs. Species of the same ecomorph are parapatric or allopatric, whereas species belonging to different ecomorphs overlap their ranges. The phylo‐spatial reconstructions suggest that the shift from allopatry to sympatry is associated with relaxation of competitive interactions. Reconstruction of species past dispersal implies that sympatry is of secondary origin. Main conclusions Interspecific competition presumably controls evolutionary and ecological dynamics in subterranean environments in a similar way as in more familiar surface environments.