Abstract
Evidence for a general lack of genetic differentiation of intertidal invertebrate assemblages in the North Atlantic, based on mtDNA sequence variation, has been interpreted as resulting from recent colonization following the Last Glacial Maximum. In the present study, the phylogeographic patterns of one nuclear and one mtDNA gene fragments of two isopods, Stenosoma lancifer (Miers, 1881) and Stenosoma acuminatum Leach, 1814, from the northeast Atlantic were investigated. These organisms have direct development, which makes them poor dispersers, and are therefore expected to maintain signatures of past historical events in their genomes. Lack of genetic structure, significant deviations from neutrality and star-like haplotype networks have been observed for both mtDNA and nuclear markers of S. lancifer , as well as for the mtDNA of S. acuminatum . No sequence variation was observed for the nuclear gene fragment of S. acuminatum . These results suggest a scenario of recent colonization and demographic expansion and/or high population connectivity driven by ocean currents and sporadic long-distance dispersal through rafting.
Highlights
Pleistocenic glaciations are known to have played a major role in shaping the phylogeographic patterns of many organisms, during the Last Glacial Maxima (LGM) (e.g. Hewitt 2004, Maggs et al 2008)
These distributional changes resulted in a typical latitudinal gradient of genetic diversity, with higher levels of diversity in southern locations, which served as glacial refugial areas, and with low genetic diversity in the north, where extinctions followed bycolonizations have occurred (Taberlet et al 1998, Hewitt 1999, Luttikhuizen et al 2008)
Alignments for the c oxidase (COI) gene included a total of 512 bp for S. acuminatum, and 566 bp for S. lancifer
Summary
Pleistocenic glaciations are known to have played a major role in shaping the phylogeographic patterns of many organisms, during the Last Glacial Maxima (LGM) (e.g. Hewitt 2004, Maggs et al 2008). Recent phylogeographic studies have challenged the classical perspective of strictly southern glacial refuges and several studies have uncovered patterns suggesting the existence of glacial refuges for cold-water species in northern areas (Provan and Bennett 2008) These findings showed that the entire northeast Atlantic region has played an important role in the diversification of species, especially in the case of cold-water species. Examples of such refugial areas are located in the northwest of the Iberian Peninsula, in the Bay of Biscay, in the English Channel and even in the North Sea (see for a review Kettle et al 2010). Secondary contact between different re-colonizing lineages originating in southern glacial refuges could explain the patterns observed in those regions (Coyer et al 2003, Gómez et al 2007, Maggs et al 2008)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
