Sonneratia ovata Backer–A genetically depauperate mangrove species

It is expected that geographically widespread and outcrossing tree species would have high level of genetic variation. Three chloroplast regions and six nuclear genes were sequenced to assess the genetic variation of a species of mangroves, Sonneratia ovata, from China and Thailand. No nucleotide polymorphism was found in the three chloroplast regions and in the six nuclear genes from all of the four populations examined. The depauperation of polymorphism in S. ovata in comparison to moderate polymorphisms of other congeneric species is surprising, particularly considering high level of polymorphism in the past and relatively wide geographic distribution of the species. Since multiple independent loci were surveyed in this study, the most plausible explanation for our observation is that S. ovata has experienced severe demographic bottlenecks in the Pleistocene glaciation, followed by subsequent recolonization by sea currents in China and Southeast Asia regions. The lack of polymorphism may also be attributable to its small population size, despite its wide geographic distribution.