Abstract
Species are the basic units for measuring biodiversity and for comprehending biological interactions. Yet, their delineation is often contentious, especially in groups that are both diverse and phenotypically conservative. Three cryptic species of long‐eared bats, Plecotus auritus, P. austriacus, and P. macrobullaris, co‐occur over extensive areas of Western Europe. The latter is a fairly recent discovery, questioning the overall diversity of the entire Plecotus complex. Yet, high morphological and acoustic similarities compromise the reliable identification of long‐eared bats in the field. We postulate that such extensive phenotypic overlap, along with the recurrent observation of morphologically intermediate individuals, may hide rampant interspecific hybridization. Based on a geographic sampling centered on areas of sympatry in the Alps and Corsica, we assessed the level of reproductive isolation of these three Plecotus species with mitochondrial and nuclear markers, looking at both inter‐ and intraspecific genetic population structuring. No sign of hybridization was detected between these three species that appear well separated biologically. Genetic structuring of populations, however, reflected different species‐specific responses to environmental connectivity, that is, to the presence of orographic or sea barriers. While the Alpine range and the Ligurian Sea coincided with sharp genetic discontinuities in P. macrobullaris and P. austriacus, the more ubiquitous P. auritus showed no significant population structuration. There were clear phylogeographic discrepancies between microsatellite and mitochondrial markers at the intraspecific level, however, which challenges the reliance on simple barcoding approaches for the delineation of sound conservation units.
Highlights
Among the tens of species concepts proposed in the literature, the most widely used is the biological species concept, coined by Mayr (1963) who defined species as “groups of or potentially in‐ terbreeding natural populations, which are reproductively isolated from other such groups.” it is accepted that many well‐recognized species can interbreed to some extent without implying necessarily the lumping of the involved taxa (Harrison & Larson, 2014; Kane et al, 2009)
Our genetic analyses, combining mitochondrial and nuclear markers, showed no evidence of interspecific admixture between the three long‐eared bat species in the Alpine and adjacent areas, where their distributions overlap extensively. These cryptic species mate assortatively based on other clues than external morphology
Despite striking phenotypic similarities, species‐spe‐ cific responses to topographic barriers could be evidenced, which correlated to distinct local altitudinal preferences of the species
Summary
Among the tens of species concepts proposed in the literature, the most widely used is the biological species concept, coined by Mayr (1963) who defined species as “groups of or potentially in‐ terbreeding natural populations, which are reproductively isolated from other such groups.” it is accepted that many well‐recognized species can interbreed to some extent without implying necessarily the lumping of the involved taxa (Harrison & Larson, 2014; Kane et al, 2009). Since two or more of these morphologically similar species of long‐eared bats occur in sympatry over extensive areas in con‐ tinental Europe and Corsica (Andriollo & Ruedi, 2018; Courtois, Rist, & Beuneux, 2011; Gilliéron, Schönbächler, Rochet, & Ruedi, 2015; Rutishauser, Bontadina, Braunisch, Ashrafi, & Arlettaz, 2012; Tvrtković, Pavlinić, & Haring, 2005), they offer the opportunity to compare the barrier effect of major landscape features on gene flow in each species in parallel. We used a combination of nuclear and mtDNA markers on bats sampled in areas where those species co‐occur in strict sympatry to explore (a) their degree of reproductive isolation and (b) to which extent the Alpine range and Ligurian Sea constitute topographic bar‐ riers limiting gene flow among populations
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