Ows less accurate fidelity for the natal internet site ?is perhaps the most effective documented (Prugnolle and De Mee^s 2002). Evolutionary lineages of distinct mitochonu drial haplotypes (matrilines) are generally linked with distinct colonies in bats (Rossiter et al. 2005), linked to distinctive nursery places in sharks (Keeney et al. 2005) or correspond to unique nesting groups in turtles (Bowen et al. 2004; Stiebens et al. 2013). Whilst matrilines may differ from each other by as handful of as one mutation step (Keeney et al. 2005; Levin and Parker 2012), larger variations have also been reported (Tillett et al. 2012). The usual signature of sex-biased dispersal shows that uni-parentally inherited loci (such as mitochondrial DNA of female vertebrates) possess a stronger signature of differentiation amongst philopatric places than bi-parentally inherited loci (Pardini et al. 2001; Bowen et al. 2004). Theoretically, sex-biased dispersal is interpreted as an evolutionary mechanism of inbreeding avoidance, no matter whether by way of the existence of genetic variations between the dispersive as well as the philopatric sex (Berg et al. 1998) or by means of the movement with the dispersing sex so that you can stay clear of kin mating (Dobson 2013). Recent proof showed that despite female philopatry amongst endangered loggerhead turtles, male-biased opportunistic mating is vital to retain the genetic diversity ?and hence the adaptive possible ?of the species by growing gene flow amongst nesting locations and preserve high genetic diversity (Stiebens et al. 2013). The identification of cryptic genetic structure is therefore critical to estimate the adaptive potential of species. The European eel (Anguilla anguilla) can be a hugely migratory fish using a life cycle that uses the entire North Atlantic basin. Born in the Sargasso Sea, eels are passively transported towards the European coasts with the major ocean currents. This connection is facilitated by the North Atlantic gyre (Blanke et al. 2012) PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/21098350 and, in unique, by an oceanic pathway linking the spawning grounds together with the Gulf Stream (Baltazar-Soares et al. 2014). Upon sexual maturity, all adult eels aim to return towards the Sargasso Sea to mate. Recent investigations on speciation and historical demography further reinforce the intrinsic function of the Gulf Stream on this species’ evolution (Jacobsen et al. 2014a): by the beginning in the 1980s, the juveniles arriving at European coasts ?hereafter known as recruitment ?experienced a steep decline (Moriarty 1990). This was followed by consecutive years of incredibly low recruitment affecting the abundance of adult eels in theircontinental range (Astrom and Dekker 2007). It is actually thought that a multitude of components have contributed to this decline: alterations in ocean currents (Baltazar-Soares et al. 2014) and ocean productivity (Friedland et al. 2007), diseases (Van Nieuwstadt et al. 2001; Kirk 2003), pollution (Robinet and Feunteun 2002), lowered freshwater habitats (DKM 2-93 Prigge et al. 2013), overfishing (Dekker 2003) and lack of spawners (Dekker 2003) are amongst probably the most consensual hypotheses. The European eel population is perceived as a single panmictic reproductive unit (Als et al. 2011) with singlegeneration local selection sorting genotypes in European freshwater systems (Pujolar et al. 2014b). Nonetheless, after the recruitment collapse, punctual observations of genetic structure amongst coastal locations were detected (Avise et al. 1986; Wirth and Bernatchez 2001; Dannewitz et al. 2005; Baltazar-Soar.