Last Glacial Maximum diversification implicated by continent-wide population structure in an avian top predator, the great horned owl (Bubo virginianus).

Abstract

Many North American species have diversified in response to past climate change, but the specific impacts of late Pleistocene glaciations on diversification and population structure in widespread North American species are uncertain. We tested drivers of continent-wide population genomic structure in North American great horned owls (Bubo virginianus). Using species distribution modeling and reduced representation genomic sequencing on 114 specimen-vouchered samples, we quantified genetic diversity, gene flow, and population divergence times to test the drivers of population structure. Specifically, we examined how contemporary and historical processes shaped this species' spatial patterns of genetic structure. We identified three populations corresponding to eastern, northwestern, and southwestern North America. Areas of relatively high effective genetic diversity corresponded to regions of high habitat suitability during the Last Glacial Maximum (LGM) and gene flow was low among recently diverged populations. Landscape genomic models accounting for least-cost path dispersal distances during the LGM and current landscape found support for both contemporary and historical geographic features driving genomic differentiation. Our results revealed how habitat fragmentation associated with historical and contemporary landscapes drove population structuring. Late Pleistocene glaciations, as recently as the LGM, seem to have driven population structure of this geographically widespread, charismatic, and large-bodied avian species.