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Fine- and regional-scale genetic structure of the exotic ascidian Styela clava (Tunicata) in south-west England, 50 years after its introduction.

Abstract : Styela clava, an ascidian native to the north-west Pacific, was first recorded in the Atlantic at Plymouth, SW England, in 1953. It now ranges in the NE Atlantic from Portugal to northern Denmark, and has colonised the east coast of North America. Within the region of first introduction, we aimed to characterize current genetic diversity in the species, elucidate the respective roles of human-aided vs. natural dispersal, and assess the extent of larval dispersal by looking for genetic differentiation at very small scales. Eight sites, mostly marinas, were studied along c. 200 km of coast in SW England encompassing Plymouth. Five microsatellite loci were genotyped in 303 individuals to analyze gene flow at regional (among sites) and fine (within sites) scales. F-statistics and assignment tests were used to investigate regional genetic structure. At the fine scale, deviation from mutation-drift equilibrium was tested, and isolation by distance and genetic clustering analyses were undertaken. Significant genetic differentiation existed between sites, unrelated to geographical separation; migration between geographically distant marinas was inferred, highlighting the likely importance of human-mediated dispersal in range expansion and occupancy by S. clava. Fine-scale population structure was present within at least four sites, which may be explained by the limited dispersal ability of this ascidian and recruitment from differentiated pools of larvae. Populations in enclosed marinas had higher self-recruitment rates than those in open sites. Some marinas might therefore function as reservoirs of propagules for subsequent spread whereas others might be sinks for migrants.
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Submitted on : Monday, February 1, 2010 - 1:50:11 PM
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Lise Dupont, Frédérique Viard, M. J. Dowell, C. Wood, J.D.D. Bishop. Fine- and regional-scale genetic structure of the exotic ascidian Styela clava (Tunicata) in south-west England, 50 years after its introduction.. Molecular Ecology, Wiley, 2009, 18, pp.442-453. ⟨10.1111/j.1365-294X.2008.04045.x⟩. ⟨bioemco-00452044⟩



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