Biogeographic Barriers and the Development of Marine Biodiversity

The biogeographically ‘ open ’ nature of marine systems is discussed. Narrow endemism is demonstrated in crustacean taxa with planktotrophic larvae, as well as in those with benthic recruitment. A close similarity is demonstrated between the endemicity on islands of shallow-water marine amphipods and that of terrestrial plants. Using comparable collecting techniques, the marine amphipod diversity of tropical lagoons (in Papua New Guinea and in New Caledonia), with different evolutionary histories forc. 60 Ma, was compared. Whilst only about 20% of the species were common to the two lagoons, the number of species collected and the family species richness was strikingly similar. This suggests the existence of evolutionary ‘ assembly rules ’. There is a weak correlation between amphipod species richness and family richness for a given area.