A study of climate niche modeling of the Eurasian Nuthatch (Sitta europaea) in theAlborz and Zagros mountains

Two opposing questions concerning differences among ecological niches of closely-related taxa in similar or adjacent habitats have long been a subject of debate. Did different populations of a species inhabit different ecological niches and undergo speciation due to the interruption of gene flow, or did speciation occur earlier, which later on caused closely-related taxa to inhabit similar habitats? In this study, we investigated the differences between the ecological niche climate of two subspecies of the Eurasian nuthatch (rubiginosa and persica), and the impact such differences had on speciation of these subspecies over different time scales, from the past to the present. To do so, we performed tests of niche equivalency and modeled niche similarities in geographical and environmental spaces of the Alborz and Zagros Mountains. Results revealed that the ecological niche climate overlap between clades of the Alborz and Zagros is insignificant, and tests of niche similarity and niche equivalency between the two subspecies of these mountain ranges were significant. Thus, niche conservatism could be inferred for these subspecies, highlighting the speciation of each subspecies in geographically allopatric regions, prior to their migration to the Alborz and Zagros Mountains. Our results suggest that each population of the Eurasian nuthatch in these ranges could be regarded as an evolutionary significant unit, and each subspecies requires proper conservation management.