A comparison between species diversities of polychaetes from tropical and temperate structurally similar rocky intertidal habitats.

Structurally similar intertidal vermetid reefs built by Dendropoma species occur in the tropical Gulf of Elat (Red Sea) and in the temperate Mediterranean coast of Israel. A comparison of the polychaete communities of these reefs yielded a higher species richness and a significantly greater species diversity in the Gulf of Elat than in the Mediterranean (90 and 70 species, H = 2.989 and H = 2.292 nats, respectively). Physical disturbances seem more intense and frequent in the Mediterranean, and the 'intermediate disturbance hypotheses' explains the relatively smaller body size and the relatively larger proportion of presumed 'migrant' species, but not the much denser populations in the Mediterranean than in the Red Sea community. The Red Sea species pool seems larger than the Mediterranean one, but the fact that there are fewer Red Sea 'migrant' species in the Red Sea community invalidates the 'equal chance hypothesis'. The greater mean species packing within genera, the proportionally larger animals, and the greater trophic diversity of the tropical than of the temperate community are in accordance with the 'niche diversification hypothesis'.-from Authors