Diversity gradients
None of the three diversity indices (species richness, phylogenetic diversity (Faith’s PD) and functional diversity (FRic) was related clearly to elevation and in all cases, there was substantial variation across sites (Fig. S4). After controlling for species richness, however, elevation affected phylogenetic composition such that communities at higher elevations (>1000 m) consisted of species that were more closely related than expected by chance (Fig. 2) – i.e., smaller-bodied river chats, forktails, wagtails and Brown Dipper. SES_MFD and SES_MPD also indicated that communities were functionally more clustered by traits and phylogeny at higher elevation, with this effect marginally weaker for functional (R2 = 0.43) than phylogenetic (R2 = 0.47) composition (Fig. 2).