Genetic Structure of the Tropical Tree Eusideroxylon zwageri in Indonesia Revealed by Chloroplast DNA Phylogeography

Eusideroxylon zwageri is a large tropical rainforest tree native to Indonesia, Malaysia, the Philippines, and Brunei. Because of its high economic value, illegal logging and overexploitation is threatening this species in several locations in Indonesia. In this study, in order to conserve genetic resources, we investigated the genetic structure of E. zwageri in Indonesia using chloroplast DNA sequencing. Eusideroxylon zwageri samples were collected from the Kalimantan (56 trees from seven populations) and Sumatra (16 trees from two populations) islands of Indonesia. Approximately 3137 bp of chloroplast DNA was sequenced for each tree. Twenty-one haplotypes were identified, of which six haplotypes were detected from two or three populations, whereas the other 15 haplotypes were detected from one population each. For each population, one to six haplotypes were detected, and phylogenetically closer haplotypes were detected within the same population. Although the haplotypes were roughly divided into two groups, geographically-close populations did not always have phylogenetically-close haplotypes. Our results suggest that in Indonesia, E. zwageri showed a high genetic diversity at the chloroplast DNA level, and populations within a population were derived from similar maternal lineages. Therefore, transplantation within a population may be a feasible option for E. zwageri conservation. However, transplantation among different populations should be conducted with careful consideration, because geographic distances are not always related to phylogenetic distances in E. zwageri.