Genetic structure and distribution of microsatellite population genetic diversity in Posidonia oceanica in the Mediterranean basin

The population genetic structure within and between 33 Posidonia oceanica meadows, sampled in the Mediterranean basin from Spain to Turkey, was analysed using microsatellite DNA markers. The populations analysed ranged from being uniclonal (in the North Adriatic) to having more than 50% of diverse genotypes. Cluster analysis of (δμ)² genetic distance showed the existence of three population groups, characterised by the presence of north Tyrrhenian, south Tyrrhenian and eastern Mediterranean populations, respectively. Population groups reflect genetic isolation caused by reduced gene flow related to present and past current regimes and to post-glacial re-colonisation events. Low genetic polymorphism and different scales of population genetic sub-structure are present in P. oceanica and could be significant to the capacity for survival and expansion of the species in the highly impacted coastal Mediterranean environment.