REITZEL, A.R.*; DARLING, J.; Boston University; Boston University: Global population structure of the invasive salt marsh anemone Nematostella vectensis

Nematostella vectensis is a euryhaline, burrowing anemone inhabiting estuarine sediments along the Atlantic, Gulf, and Pacific coasts of North America, as well as the southern and southeastern coasts of England. The species is currently listed as �vulnerable� in the IUCN Invertebrate Red Data Book and receives protection in Britain under The Wildlife and Countryside Act. Recent genetic studies of English populations have revealed a striking genetic structure, largely clonal in nature and dominated by a single genotype. Using amplified fragment length polymorphism (AFLP) fingerprinting, we have extended this research to investigate the relationship between Nematostella populations distributed throughout much of the species� global range. Our findings indicate the prevalence of clonal populations along the Atlantic and Pacific US coasts, and ecological considerations suggest the likelihood that such local genetic homogeneity is a result of extreme founder events, rather than local adaptive sweeps. Measures of genetic relatedness indicate that the current geographic distribution is due in part to recent anthropogenic dispersal leading to opportunistic colonizations by single or few asexually reproducing individuals. We discuss implications for the conservation management of Nematostella in England, likely patterns of invasiveness, and the role of reproductive plasticity in determining the evolutionary trajectory of this species.