A European Melting Pot of Harbour Porpoise in the French Atlantic Coasts Inferred from Mitochondrial and Nuclear Data

Abstract

Field surveys have reported a global shift in harbour porpoise distribution in European waters during the last 15 years, including a return to the Atlantic coasts of France. In this study, we analyzed genetic polymorphisms at a fragment of the mitochondrial control region (mtDNA CR) and 7 nuclear microsatellite loci, for 52 animals stranded and by-caught between 2000 and 2010 along the Atlantic coasts of France. The analysis of nuclear and mitochondrial loci provided contrasting results. The mtDNA revealed two genetically distinct groups, one closely related to the Iberian and African harbour porpoises, and the second related to individuals from the more northern waters of Europe. In contrast, nuclear polymorphisms did not display such a distinction. Nuclear markers suggested that harbour porpoises behaved as a randomly mating population along the Atlantic coasts of France. The difference between the two kinds of markers can be explained by differences in their mode of inheritance, the mtDNA being maternally inherited in contrast to nuclear loci that are bi-parentally inherited. Our results provide evidence that a major proportion of the animals we sampled are admixed individuals from the two genetically distinct populations previously identified along the Iberian coasts and in the North East Atlantic. The French Atlantic coasts are clearly the place where these two previously separated populations of harbour porpoises are now admixing. The present shifts in distribution of harbour porpoises along this coast is likely caused by habitat changes that will need to be further studied.

Defining management units for cetaceans by combining genetics, morphology, acoustics and satellite tracking

“…Hence, this suggests male dispersal in the breeding season for mating purposes which is a mechanism that could serve to avoid inbreeding as seen in other mammals (e.g., Handley and Perrin, 2007). Another explanation could be that the two populations are in the process of admixing, as Alfonsi et al (2012) suggested for the harbour porpoise along the French Atlantic coast. The lack of deviation from HW expectations of the microsatellite frequencies suggested a panmictic breeding population as it only takes one generation to restore HW-expectations after two genetically different populations admix.…”

“…Block et al, 2011). In the last decades, harbour porpoises (Phocoena phocoena) have been studied intensely in European waters to identify population delimitations and to monitor the status of the species (e.g., Siebert et al, 2006, Evans and Teilmann, 2009, Wiemann et al, 2010Alfonsi et al, 2012;Fontaine et al, 2014). The main driver for this effort has been the fact that several thousand harbour porpoises are bycaught each year and drown in European gillnet fisheries (Tregenza et al, 1997;Vinther and Larsen, 2004;Bjørge et al, 2013).…”

Population structure and intergeneric hybridization in harbour porpoises Phocoena phocoena in British Columbia, Canada

“…These results contrast with those from other areas within the global range of the harbour porpoise (e.g. Wang et al 1996, Wang & Berggren 1997, Rosel et al 1999, Chivers et al 2002, Tolley & Rosel 2006, Fontaine et al 2007, Wiemann et al 2010, Alfonsi et al 2012, De Luna et al 2012). In particular, Chivers et al (2002) suggested more subdivision of harbour porpoises within the same region that we studied.…”

“…Some or all of these subspecies comprise a set of spatially structured populations (e.g. Wang et al 1996, Wang & Berggren 1997, Rosel et al 1999, Tolley & Rosel 2006, Fontaine et al 2007, Alfonsi et al 2012. To date, the majority of studies have focused on northeastern Atlantic and Baltic Sea population groups.…”

“…We focused on the population structure of harbour porpoises in the Strait of Georgia because of the species abundance and because of the numerous anthropogenic threats to harbour porpoises in this area. Given the patterns of population subdivision in other areas of the species' range (Fontaine et al 2007, Alfonsi et al 2012, we expected harbour porpoises to exhibit spatially structured populations.…”