Comparative phylogeography of six Highland Ethiopian passerines in the eastern Afromontane biodiversity hotspot

Topographically complex montane regions in the tropics harbor high biodiversity and drive diversification. Located within the East Africa Biodiversity Hotspot, the Ethiopian Highlands are one such montane region of high species diversity but disproportionately undescribed genetic diversity. Montane habitats of the Ethiopian Highlands are divided by lowland barriers including the Blue Nile Valley (BNV) and Great Rift Valley (GRV). These lowland barriers have shaped phylogeographic patterns in sedentary taxa like frogs and rodents but the relative effects of the GRV and BNV have not been assessed in dispersive taxa such as birds. We used whole genome resequencing data from six codistributed highland songbirds to assess comparative patterns of phylogeographic structure in our focal species and how those compare to patterns in other taxonomic groups. Generally, we found that populations separated by the GRV are more differentiated than populations separated by the BNV, but also that species appeared to respond idiosyncratically. The phylogeographic structure found in these taxa have similarities and differences with previous work in frogs and rodents, but overall, no single pattern is consistent across taxonomic groups. Within taxa, genetic diversity was broadly consistent across localities and was explained by harmonic mean NE through time, although there were noticeable reductions in one population each of two species. Here, we showed that highland topography impacts the diversification of even the most dispersive Ethiopian taxa by quantifying population genetic variation of six avian species in the East Africa Biodiversity Hotspot.

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