Phylogeography of Kandelia candel in East Asiatic mangroves based on nucleotide variation of chloroplast and mitochondrial DNAs

Vivipary with precocious seedlings in mangrove plants was thought to be a h indrance to long-range dispersal. To examine the extent of seedling dispers al across oceans, we investigated the phylogeny and genetic structure among East Asiatic populations of Kandelia candel based on organelle DNAs. In to tal, three, 28 and seven haplotypes of the chloroplast DNA (cpDNA) atpB-rbc L spacer, cpDNA trnL-trnF spacer, and mitochondrial DNA (mtDNA) internal tr anscribed spacer (ITS) were identified, respectively, from 202 individuals. Three data sets suggested consistent phylogenies recovering two differenti ated lineages corresponding to geographical regions, i.e. northern South-Ch ina-Sea + East-China-Sea region and southern South-China-Sea region (Sarawa k). Phylogenetically, the Sarawak population was closely related to the Ran ong population of western Peninsula Malaysia instead of other South-China-S ea populations, indicating its possible origin from the Indian Ocean Rim. N o geographical subdivision was detected within the northern geographical re gion. An analysis of molecular variance (AMOVA) revealed low levels of gene tic differentiation between and within mainland and island populations (Phi (CT)=0.0151 Phi (SC) = 0.037), indicating conspicuous long-distance seedli ng dispersal across oceans. Significant linkage disequilibrium excluded the possibility of recurrent homoplasious mutations as the major force causing phylogenetic discrepancy between mtDNA and the trnL-trnF spacer within the northern region. Instead, relative ages of alleles contributed to nonrando m chlorotype-mitotype associations and tree inconsistency. Widespread distr ibution and random associations (chi (2) = 0.822, P = 0.189) of eight hypot hetical ancestral cytotypes indicated the panmixis of populations of the no rthern. geographical region as a whole. In contrast, rare and recently evol ved alleles were restricted to marginal populations, revealing some prefere ntial directional migration.