POPULATION STRUCTURE OF TWO BENTHIC SPECIES WITH DIFFERENT LARVAL STAGES IN THE EASTERN MEDITERRANEAN SEA

Population structure in the marine environment is sometimes cryptic due to complex demographic expansion and distribution of the species. Benthic organisms possess different reproductive strategies with regards to larvae dispersal ability. The hypothesis of variation in biogeographic structure in two benthic species, sea urchin Paracentrotus lividus and ascidian Microcosmus sabatieri using Random Amplified Polymorphism (RAPD) was tested. Analyses indicate near panmixia and low but significant genetic differentiation between Amvrakikos Gulf and open sean P. lividus, mostly attributed to the documented nanism in the area. M. sabatieri populations showed substantial genetic differentiation over a latitudinal gradient. Results suggest that benthic species with a long-lived larval phase favour large geographical dispersal while those with a short-lived phase utilise a shorter dispersal range.