Interspecific introgression in cetaceans: DNA markers reveal post-F1 status of a pilot whale.

Laura Miralles,Santiago Lens,Antonio Rodríguez-Folgar,Manuel Carrillo,Vidal Martín,Eva Garcia-Vazquez,Bjarni Mikkelsen,Tom Gilbert

doi:10.1371/journal.pone.0069511

Abstract

Visual species identification of cetacean strandings is difficult, especially when dead specimens are degraded and/or species are morphologically similar. The two recognised pilot whale species (Globicephala melas and Globicephala macrorhynchus) are sympatric in the North Atlantic Ocean. These species are very similar in external appearance and their morphometric characteristics partially overlap; thus visual identification is not always reliable. Genetic species identification ensures correct identification of specimens. Here we have employed one mitochondrial (D-Loop region) and eight nuclear loci (microsatellites) as genetic markers to identify six stranded pilot whales found in Galicia (Northwest Spain), one of them of ambiguous phenotype. DNA analyses yielded positive amplification of all loci and enabled species identification. Nuclear microsatellite DNA genotypes revealed mixed ancestry for one individual, identified as a post-F1 interspecific hybrid employing two different Bayesian methods. From the mitochondrial sequence the maternal species was Globicephala melas. This is the first hybrid documented between Globicephala melas and G. macrorhynchus, and the first post-F1 hybrid genetically identified between cetaceans, revealing interspecific genetic introgression in marine mammals. We propose to add nuclear loci to genetic databases for cetacean species identification in order to detect hybrid individuals.

Highlights

In a progressively threatened oceanic environment where large species are more and more endangered, cetacean monitoring is increasingly important for estimating population censuses and early detecting signals of species depletion [1]
Van Bree [4] demonstrated that they are two clearly distinct species; their external appearance is similar and the morphometric characteristics employed to visual species discrimination partially overlap [5]
Genetic species identification in cetaceans is generally based on maternally inherited mitochondrial DNA

Summary

Introduction

In a progressively threatened oceanic environment where large species are more and more endangered, cetacean monitoring is increasingly important for estimating population censuses and early detecting signals of species depletion [1]. The two recognised pilot whale species, Globicephala melas and G. macrorhynchus, are cetaceans of charismatic behaviour. Genetic species identification in cetaceans is generally based on maternally inherited mitochondrial DNA (mtDNA).

Results

Conclusion