Abstract
Pilot whales are two cetacean species (Globicephala melas and G. macrorhynchus) whose distributions are correlated with water temperature and partially overlap in some areas like the North Atlantic Ocean. In the context of global warming, distribution range shifts are expected to occur in species affected by temperature. Consequently, a northward displacement of the tropical pilot whale G. macrorynchus is expected, eventually leading to increased secondary contact areas and opportunities for interspecific hybridization. Here, we describe genetic evidences of recurrent hybridization between pilot whales in northeast Atlantic Ocean. Based on mitochondrial DNA sequences and microsatellite loci, asymmetric introgression of G. macrorhynchus genes into G. melas was observed. For the latter species, a significant correlation was found between historical population growth rate estimates and paleotemperature oscillations. Introgressive hybridization, current temperature increases and lower genetic variation in G. melas suggest that this species could be at risk in its northern range. Under increasing environmental and human-mediated stressors in the North Atlantic Ocean, it seems recommendable to develop a conservation program for G. melas.
Highlights
Global environmental changes, including temperature increase, glacial ice melting and sea level rising, are intense in the northern latitudes where they are reshaping the fragile local ecosystems with potentially devastating consequences for vulnerable species [1]
There, the sea surface temperature (SST) warming was more intense during summer months (Fig 2B), coincident with the reproduction season of pilot whales
The other hybrid was morphologically identified as G. melas, and genetically assigned to G. melas from nuclear markers, but had G. macrorhynchus-type mitochondrial DNA. This evident morphological and nuclear-mitochondrial discordance can be caused by repeated backcrosses of a hybrid issued from a cross [G. macrorhynchus female x G. melas male] to G. melas. These findings demonstrate that introgression is asymmetrical, with the genome of G. macrorhynchus entering into G. melas genome and not in the opposite direction
Summary
Global environmental changes, including temperature increase, glacial ice melting and sea level rising, are intense in the northern latitudes where they are reshaping the fragile local ecosystems with potentially devastating consequences for vulnerable species [1]. Amongst other consequences of global change, a general increase of interspecific hybridization is predicted in Polar and subpolar zones due to the loss of temperature barriers [2] and the arrival of new PLOS ONE | DOI:10.1371/journal.pone.0160080. Hybridization and Asymmetric Introgression in Northern Pilot Whales collection and analysis, decision to publish, or preparation of the manuscript Amongst other consequences of global change, a general increase of interspecific hybridization is predicted in Polar and subpolar zones due to the loss of temperature barriers [2] and the arrival of new PLOS ONE | DOI:10.1371/journal.pone.0160080 August 10, 2016
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