Genetic differentiation among populations of the Mediterranean hermaphroditic brooding coral Balanophyllia europaea (Scleractinia, Dendrophylliidae)

Spatial models of genetic structure and potential gene flow were determined for five populations of Balanophyllia europaea, a simultaneous hermaphroditic and brooding coral, endemic to the Mediterranean. Six allozyme loci indicated a genetic structure that departed markedly from the Hardy-Weinberg equilibrium with a significant lack of heterozygotes. The genetic structure observed supports the hypothesis that self-fertilization characterizes the reproductive biology of B. europaea. Populations at small spatial scales (8-40 m) are genetically connected, while those at large scales (36 – 1941 km) are genetically fragmented; the genetic differentiation of the populations is not correlated to geographic separation. This spatial model of genetic structure is compatible with an inbreeding mating system. Furthermore, it is also consistent with the expected dispersal potential of swimming larvae of brooding corals, i. e. larvae that are able to produce significant gene flows only within limited spatial scales.