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

et al. (2012) A European Melting Pot of Harbour Porpoise in the French Atlantic Coasts Inferred from Mitochondrial and Nuclear Data. PLoS ONE 7(9): e44425. doi:10.1371/journal.pone.0044425 A European Melting Pot of Harbour Porpoise in the French Atlantic Coasts Inferred from Mitochondrial and Nuclear Data Eric Alfonsi 0 1 Sami Hassani 0 1 Franc ois-Gilles Carpentier 0 1 Jean-Yves Le Clec'h 0 1 Willy Dabin 0 1 Olivier Van Canneyt 0 1 Michael C. Fontaine 0 1 Jean-Luc Jung 0 1 Sharyn Jane Goldstien, University of Canterbury, New Zealand 0 Current address: Department of Biological Sciences, University of Notre Dame , Notre Dame, Indiana , United States of America 1 1 Laboratoire BioGeMME (Biologie et Ge ne tique des Mammife`res Marins dans leur Environnement), Universite Europe enne de Bretagne & Universite de Bretagne Occidentale, Brest, France, 2 Laboratoire d'Etude des Mammife`res Marins , Oce anopolis, Brest, France, 3 LEMAR , Universite Europe enne de Bretagne & Universite de Bretagne Occidentale , Brest, France, 4 Observatoire PELAGIS, UMS 3462 , CNRS-Universite de La Rochelle, La Rochelle, France, 5 Laboratoire d'Ecologie, Syste matique et Evolution, Universite Paris-Sud - CNRS, Orsay, France, 6 Ecoanthropologie et d'Ethnobiologie, UMR 5145, CNRS-MNHN-Universite Paris 7 Muse e de l'Homme , Paris , France 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 biparentally 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. - Funding: Eric Alfonsi is supported by a grant Cifre of the ANRT (Association Nationale de la Recherche et de la Technologie, http://www.anrt.asso.fr). MCF is currently a post-doc supported by the ANR NUTGENEVOL research project. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript. Competing Interests: EA, JYLC and SH are affiliated to Oceanopolis (http://www.oceanopolis.co.uk), a public attraction (a Centre de Culture Scientifique Technique et Industrielle) which belongs to the town of Brest and is managed by Brestaim (http://www.brestaim.fr), a public-private company. This does not alter the authors adherence to all the PLoS ONE policies on sharing data and materials. . These authors contributed equally to this work. The harbour porpoise (Phocoena phocoena), one of the smallest cetaceans, is widely distributed in the cold to temperate coastal waters of the northern hemisphere. The species occurs in three major areas, the North Pacific, the North Atlantic and the Black Sea [1,2]. In the North Atlantic Ocean, it is the most common cetacean species [3]. The North Atlantic population of harbour porpoise has recently been the subject of several studies, that focused mainly on its spatial and temporal distribution [38]. From the 1940s onwards, field observations (based on strandings, by-catch and sightings) reported that harbour porpoises, commonly encountered in the southern North Sea and off the coasts of the European mainland from Spain to Denmark, declined abruptly [9,10]. More recently, the large scale field surveys SCANS I, performed in 1994 [3] and SCANS II performed in 2005 [5], estimated a constant abundance of about 385,000 harbour porpoises in the eastern part of the North Atlantic [5]. However, a comparison of these survey results also highlighted a marked shift in distribution range of the species in the European waters during a 10-year period. More commonly distributed in the northern part of the North Sea in 1994, the surveys conducted in 2005 detected higher abundances of harbour porpoises along the south-east coast of the United Kingdom and in the Celtic Sea. In the eastern part of the North Atlantic, the harbour porpoises clearly experienced a global southward shift going on for some years. Local studies confirmed this shift in distribution, and the return of harbour porpoises have been clearly documented along Dutch [11], German [6,12], Southwest Britain [13] and French coasts [8]. However, the reasons for these global movements are not clearly understood. Reijinders [10] argued that a mix of environmental changes and of direct anthropogenic impacts could be involved (e.g. variations in the availability of prey, especially herring and mackerel, and by-catch in fishing nets). Indeed, the repartition of harbour porpoises is expected to be strongly tied to variation in the primary and secondary productivity that provides the basis for apex consumers [1416]. Harbour porpoises display an energy demanding reproductive schedule [14], as females are often gestating and lactating at the same time and parturition occurs shortly before mating [17]. Their small body size also limits their ability to store energy [18]. Taken together, these factors suggest that harbour porpoises must feed frequently without prolonged periods of fasting. Relatively continuous accessibility to adequate prey is therefore critical, and any changes in prey availability may affect energy stores, and ultimately survival [19]. Thus, temporary shortages in prey availability can have negative impacts on these animals and are likely to be responsible for changes in their distribution [2023]. Harbour porpoises also suffer considerable mortality due to accidental by-catches in certain commercial fisheries. For instance, a clear increase in the proportion of by-catch among the stranded harbour porpoises along the coasts of Brittany in North West of France has been observed in the winter months [8]. Although the population of ha (...truncated)