High proportion of smaller ranged hummingbird species coincides with ecological specialization across the Americas

Ecological communities that experience stable climate conditions have been speculated to preserve more specialized interspecific associations and have higher proportions of smaller ranged species (SRS). Thus, areas with disproportionally large numbers of SRS are expected to coincide geographically with a high degree of community-level ecological specialization, but this suggestion remains poorly supported with empirical evidence. Here, we analysed data for hummingbirdresource specialization, range size, contemporary climate, and Late Quaternary climate stability for 46 hummingbird–plant mutualistic networks distributed across the Americas, representing 130 hummingbirdspecies (ca 40% of all hummingbirdspecies). We demonstrate a positive relationship between the proportion of SRS of hummingbirdsand community-level specialization, i.e. the division of the floral niche among coexisting hummingbirdspecies. This relationship remained strong even when accounting for climate, furthermore, the effect of SRS o...