GENETIC VARIATION AND OUTCROSSING RATES OF THE ENDANGERED TROPICAL SPECIES <em>DIPTEROCARPUS</em> <em>DYERI</em>

Abstract

Dipterocarpus dyeri is an endangered species in lowland tropical forests of Vietnam because of habitat fragmentation and over-exploitation of this species. It plays an important economic and ecological role in Vietnam. Due to the importance and lack of information on its genetic diversity and mating system, we investigated genetic parameters in adults and juveniles of this species in two natural populations about 10 km apart. Eight polymorphic microsatellite loci were analysed and showed high genetic diversity in adults (H_O = 0.475–0.563, H_E = 0.551–0.649) and juveniles (H_O = 0.47–0.513, H_E = 0.576–0.685) in both populations. Results revealed differences of genetic diversity between two adult (F_ST = 0.123) and two juvenile populations (F_ST = 0.188). However, the differences were negligible and indicated that the fragmented habitat had negligible effect on genetic diversity. Gene flow or gene migration between two populations in adults or juveniles remained (N_m > 1), although this value reduced slightly in the latter. Analysis of the mating system indicated high outcrossing rate of D. dyeri (t_m = 0.8). Biparental mating (t_m – t_s) was relatively high (0.19–0.25) and suggested high tendency of mating system between relatives. Genetic conservation should derive from correlated outcrossing.