Plant material
Natural populations with over 10 individuals of H. littoralis were found at only four sites in China: Xiangkeng (0.6 ha, 148
individuals), Yanzao (0.7 ha, 1350 individuals), Qinglan (1.33 ha, 502 individuals), and Fangchenggang (2.5 ha, 515 individuals).
All four sites, which together represent more than 90% of the range of this species in China, were on the coast of the
South China Sea, and each site contained both mangrove and non-mangrove stands of H. littoralis. The four sites were
separated from each other by distances ranging from 60 to 700 km (Fig. 1). Within each site, disjunctive stands that grew
either in mangrove swamps or in non-mangrove areas were considered as separate populations in this study, since its genetic
structure was to be explored. A total of 146 individuals from these eight natural populations of H. littoralis were sampled
(Table 1). Leaf materials from 16 to 20 randomly selected trees at intervals of at least 5mwere collected throughout the entire
range of each population. Leaves were stored with silica gel in zip-lock plastic bags until DNA isolation.