Population genetic variation, differentiation and bottlenecks of Dacrydium pectinatum (Podocarpaceae) in Hainan Island, China: implications for its conservation

摘要

Island populations provide an ideal natural experiment with which to study the forces driving population evolution. Seventeen populations of Dacrydium pectinatum de Laubenfels on Hainan Island, China, were sampled throughout its distribution range and then assessed using inter-simple sequence repeats (ISSR) markers. Population genetic parameters were estimated by Bayesian approaches as well as conventional methods. Genetic bottleneck signatures were further dissected by performing three heterozygosity excess tests and the mode-shift indicator test. Compared with other coniferous species, a relatively high level of genetic variation and a low degree of differentiation was revealed in D. pectinatum. In addition, severe bottlenecks were identified at local, regional as well as range-wide scale. Ecological and life-history traits were suggested to play major roles in the shaping of the genetic variation pattern. In particular, long life span could have exerted a lagging effect on both the genetic variation and differentiation of extant populations. Our findings may contribute to improving management practices for the restoration of D. pectinatum.