Abstracts (first author)
Genetic diversity and population structure of Rhizophora apiculata, a mangrove tree in central Indo-West Pacific
Population genetic analysis of mangroves can reveal their patterns of genetic diversity, which is important for understanding their evolutionary history and scientific conservation. In this study, we examined the nucleotide diversity and population differentiation in six populations of a mangrove tree, Rhizophora apiculata, from China and Thailand based on sequencing 78 nuclear genes through Illumina platform. For each population, more than 30 individuals were pooled for sequencing. The average θw and θπ of the six populations ranged from 0.000263 to 0.000786, and from 0.000258 to 0.000924, respectively, showing low levels of DNA polymorphism within each population. Fst analysis showed strong population structure at the regional level,suggesting Malay Peninsula as a barrier to restrict gene flow between the Andaman Sea and South China Sea despite the existence of the Malacca Strait. However, Fst values vary from zero to one by locus, which could not be explained by simple gene flow model. Haplotype analysis showed two highly divergent haplotypes often reside within populations, which may be caused by recent admixture. Patterns of genetic diversity in this species might result from the repeated glacial events during Plio-Pleistocene, when the Andaman Sea was isolated with South China Sea at the lowered sea level. Reduced genetic diversity in populations from South China Sea can be attributed to lower effective population size for the enormously changed shorelines during this stage. We further used Sanger method to obtain sequences of three genes among 15 populations from wider geographic regions. STRUCTRUE analysis indicated that these populations formed five clusters, corresponding to five geographic regions , which suggests population structure of this species was mainly shaped by geographic isolation. Our study reveals the effect of glacial events on patterns of genetic diversity of an intertidal mangrove tree, which will be informative for its conservation.