Phylogeography of the Oenanthe hispanica-pleschanka-cypriaca complex (Aves, Muscicapidae: Saxicolinae): Diversification history of open-habitat specialists based on climate niche models, genetic data, and morphometric data

The succession of glacials and interglacials during the Pleistocene strongly influenced the diversification and distribution patterns in birds. In contrast to species of temperate regions, open-habitat specialists should have experienced range expansion during the longer glacial periods, while range contractions occurred during the shorter interglacials. However, only few studies have tested this prediction so far. We studied the Oenanthe hispanica-pleschanka-cypriaca (Aves, Muscicapidae: Saxicolinae) complex characteristic of open habitats in the Palearctic. Based on three mitochondrial and one Z-linked nuclear marker, we inferred its phylogeny, historical diversification, and demography. Ecological niche modeling was used to reconstruct potential distributions during the last glacial maximum and the last interglacial. Using 19 morphological traits, we tested for morphometric differences among the different taxa. Mitochondrial markers revealed strong genetic differences between O.h.hispanica and the other taxa with a divergence event at around 1.7 million years ago. No consistent genetic differences were revealed between O.cypriaca, O.h.melanoleuca, and O.pleschanka. The latter two hybridize in contact zones, which might explain partly the lack of genetic differentiation; yet, further analyses using genomic data are needed to infer the true divergence history of the complex. Signs of population expansions in the clade comprising O.h.melanoleuca, O.pleschanka, and O.cypriaca at 90,000years ago coincided with the last glacial as predicted. Population expansion then was also supported by ecological climate niche models. O.h.hispanica was not consistently separated from the other taxa in morphometrics. It might nonetheless warrant species status, pending further analyses.