REITZEL, Adam M; FINNERTY, John R.; Boston University; Boston University: Local population dynamics of a widely introduced salt marsh anemone, Nematostella vectensis

Nematostella vectensis is a euryhaline, burrowing anemone primarily inhabiting tidally-restricted salt marsh pools throughout North America, as well as the parts of England. Recent population genetic data coupled with a discontinuous range support a hypothesis for multiple anthropogenic introductions. The patterns of colonization by an introduced species are dictated not solely by the broad spatial extent of its range, but also by the dynamics of the colonizing population at a local level. Here we report investigations of the spatio-temporal population dynamics at a local level by comprehensive monitoring of habitat and Nematostella populations at multiple sites in New England and determination of population genetic composition with AFLP fingerprinting. GIS mapping of suitable habitat and local populations of Nematostella suggest frequent changes in the distribution of both. Similarly, changes in local density of Nematostella and resident adult sizes support a high degree of seasonality with highest densities throughout the summer months. Population genetic data indicate independent subpopulations within a site are genetically differentiated, even from subpopulations inhabiting pools 10 m away. Subpopulations appear to harbor asexual lineages, despite the occurrence of sexual reproduction at some sites. Longitudinal population genetic data from single pools over two or more years revealed extensive or complete changes in genotype composition. Together, our results reveal a complex local population dynamic for Nematostella with rapid changes in its habitat, distribution of subpopulations, and genotype composition. We further discuss our results in context of laboratory studies of adult reproductive and larval behavior as well as studies from other parts of this species range.