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

Abstract

Vivipary with precocious seedlings in mangrove plants was thought to be a hindrance to long-range dispersal. To examine the extent of seedling dispersal across oceans, we investigated the phylogeny and genetic structure among East Asiatic populations of Kandelia candel based on organelle DNAs. In total, three, 28 and seven haplotypes of the chloroplast DNA (cpDNA) atpB-rbcL spacer, cpDNA trnL-trnF spacer, and mitochondrial DNA (mtDNA) internal transcribed spacer (ITS) were identified, respectively, from 202 individuals. Three data sets suggested consistent phylogenies recovering two differentiated lineages corresponding to geographical regions, i.e. northern South-China-Sea + East-China-Sea region and southern South-China-Sea region (Sarawak). Phylogenetically, the Sarawak population was closely related to the Ranong population of western Peninsula Malaysia instead of other South-China-Sea populations, indicating its possible origin from the Indian Ocean Rim. No geographical subdivision was detected within the northern geographical region. An analysis of molecular variance (AMOVA) revealed low levels of genetic differentiation between and within mainland and island populations (phiCT = 0.015, phiSC = 0.037), indicating conspicuous long-distance seedling 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 non-random chlorotype-mitotype associations and tree inconsistency. Widespread distribution and random associations (chi2 = 0.822, P = 0.189) of eight hypothetical ancestral cytotypes indicated the panmixis of populations of the northern geographical region as a whole. In contrast, rare and recently evolved alleles were restricted to marginal populations, revealing some preferential directional migration.

Vicariance and Oceanic Barriers Drive Contemporary Genetic Structure of Widespread Mangrove Species Sonneratia alba J. Sm in the Indo-West Pacific

“…Likewise, populations from the South China Sea were genetically divided into mainland-origin (MA3-TH3-VIE) and island-origin (MA4-PH1-PH2) ( Figure 3c); thus, the sea itself appeared to be a genetic barrier. This genetic pattern has been observed in S. alba itself [11] and also in viviparous mangrove species, Kandeliacandel [49].…”

“…In the latter, the divergence was attributed to the fruiting season that coincided with northward-flowing ocean currents cutting through the South China Sea into the Pacific Ocean, thus preventing dispersal between populations from the east and west corners of the South China Sea [49]. Landscape level propagule release simulations, which account for ocean circulation patterns, will be able to cross-validate these inferences [50].…”

Levels and patterns of DNA variation in two sympatric mangrove species, Rhizophora apiculata and R. mucronata from Thailand

“…The levels of polymorphism of cpDNA regions in C. tagal were unexpectedly high: however, it is not clear whether those cpDNA regions are also highly variable in other mangrove species. Although genetic markers such as AFLP (e.g., Giang et al, 2003), microsatellites (e.g., Maguire et al, 2000), cpDNA (e.g., Chiang et al, 2001) and mitochondrial DNA (e.g., Chiang et al, 2001) were developed for surveys of genetic structure, phylogeography and molecular phylogeny of some mangrove species, the amount and pattern of genetic variation of functional nuclear genes in mangrove species are largely unknown. Investigation of such regions is necessary for understanding of evolutionary forces shaping genetic structure and distribution of extant populations, finding genetic factors responsible for adaptation, and providing guidelines for conservation of mangrove forests.…”

Chloroplast analysis of Zelkova schneideriana (Ulmaceae): genetic diversity, population structure, and conservation implications

“…The most diverse populations (SZ and TX) contained five haplotypes, whereas populations JR, HH, and WH only contained one haplotype each (H9, H4, and H4, respectively). Low genetic diversity at the cpDNA level in some populations is always related to demographic events (Chiang et al, 2001). The haplotype network (Figure 1) suggests that the frequency of haplotype H4 may indicate an expansion event.…”