Geographic variation and ecological adaptation in Aurelia (Scyphozoa, Semaeostomeae): some implications from molecular phylogenetics

Mitochondrial and nuclear DNA sequence data indicate considerable phylogeog raphic structure and at least five sibling species of Aurelia in the Pacifi c Ocean. At least a sixth sibling species can be found in the northwest Atl antic Ocean. These data suggest long histories of geographic and ecological sub-division and divergence of populations, which are inconsistent with cu rrent descriptions of Aurelia as a tri-typic genus in which most population s belong to one almost ubiquitous ecological generalist, A. aurita Linnaeus . Existing ecological and systematic descriptions of Aurelia, therefore, sh ould be re-evaluated in light of these molecular data. Reciprocally, such r e-evaluations should facilitate interpretation of the molecular data. Here, we introduce new DNA sequence data from Pacific and Black Sea Aurelia and novel ecological data describing tropical Aurelia inhabiting a marine lake in Palau, Micronesia. Despite large genetic distances between temperate and tropical Aurelia and the different environments inhabited by these populat ions, their rates of feeding, growth, respiration and swimming are similar. We discuss this result in terms of geographic variation and ecological ada ptation in Aurelia and also comment on population dynamics, blooms, exotic species and the systematics of Aurelia. Finally, we consider briefly the im plications of these findings for other scyphozoan species.