Mitochondrial DNA reveals the impact of Pleistocene glaciations on a widespread palearctic bat species

Abstract

Today’s biodiversity was strongly impacted by glacial cycles during the Pleistocene. They generated species diversity and population structuring, which can easily remain undetected, if populations differentiation is not accompanied by divergence in external morphological traits. This phenomenon, described as cryptic diversity, has been intensively researched in bats, which are known to harbour cryptic phylogenetic lineages. Many studies however have a regional focus or suffer from geographical gaps. Widely understudied areas include Central and Western Asia, although they connect the western and eastern Palearctic fauna. These areas are characterized by topographic heterogeneity and therefore high ecosystem diversity. In this study we investigated the phylogeography of the Savii’s pipistrelle (Hypsugo savii), a bat species assumed to be widely distributed across the Palaearctic. We compiled published sequences from four mitochondrial genes (ND1, CytB, COI and 16 S), added new sequences especially from the Asian part of the distribution range and performed phylogenetic and phylogeographic analyses. They indicate that H. savii is a taxonomic unit with extensive cryptic diversity, comprising at least four major mitochondrial lineages with allopatric or parapatric distribution ranges. Divergence time dating reveals the impact of Pleistocene glaciations on shaping highly structured populations of a highly mobile mammal across the Palearctic. Our study also revealed several zones of secondary contact among populations where hybridization and gene flow likely occur. This study highlights the necessity for studying biodiversity in Western and Central Asia in order to understand biogeographic patterns, evolutionary processes and conservation needs in the area that connects eastern and western Palearctic faunas.