095 when the Atlantic sample was included in the analysis). Blue mussel Overall F ST is 0.47 (Table 2) with a strong barrier separating two southwestern samples and a second

barrier distinguishing island and mainland samples in the Baltic Proper West. High diversity at southern sampling sites contrasted with lower diversity and higher divergence in northern samples. The strikingly high F ST might reflect species mixture and introgression. M. trossulus is indigenous to the Baltic Sea but is closely related to M. edulis (common name also blue mussel), native to the North Sea. These taxa are known to hybridize and it is possible that our southern samples include very rare M. edulis specimens. The two species are difficult to distinguish even by genetic techniques, and geographic distribution and genetic characteristics of these species are continuously GW786034 cost subject to revision (Riginos and Cunningham 2005; Steinert et al. 2012). Bladderwrack The three strongest barriers to gene flow occur in the northern part of the Baltic, although the high overall F ST (0.14; Table 2) indicated strong genetic structuring overall, with all sampling locations being significantly differentiated from each other (Table S2g). Discussion We conducted the first multi-species

study in the Baltic Sea where a large number of individuals and loci were collected from the same areas covering the full Baltic Sea. Surprisingly, we detected few shared genetic patterns in the seven species analyzed with respect to location of the three SHP099 purchase major genetic barriers to gene flow and diversity-divergence patterns (Fig. 2). An exception to this general lack of consistence is the genetic break between the Atlantic

and the Baltic Sea. We observe a variety of genetic patterns ranging from large and significant differences among sampling regions in both genetic variation and divergence, to very little differentiation within the Baltic Sea. The most pronounced, genetic breaks occurred almost individually for each species in different regions Plasmin of the Baltic Sea, although several species showed significant pairwise differentiation between the majority of the samples (Table S2a–g). At the northern extreme, five of six samples from the Bothnian Bay showed high diversity, but no shared major genetic barrier was present in this region (Table 3; Fig. 2). Unlike previous studies of herring and perch (Jørgensen et al. 2005; Olsson et al. 2011) we found few shared major genetic breaks associated with the different sub-basins of the Baltic Sea, e.g. around the Åland Islands. Potential causes of variability patterns The species-specific genetic patterns in the Baltic Sea, including relative amount of genetic variation, location of major genetic breaks, and isolation by distance are likely dependent on a multitude of factors including salinity tolerance, oceanographic features, life history, and population history (Table 1).