Population genetic structure and conservation of an endangered conifer, Cathaya argyrophylla (Pinaceae)

Cathaya argyrophylla is an endangered conifer restricted to subtropical mountains of China, with total number of individuals less than 4,000. To assess levels and patterns of genetic diversity of C. argyrophylla, eight populations representing four widely separated regions were analyzed for allozyme variation, using 13 enzymes. In comparison with other coniferous species, C. argyrophylla possesses a low amount of variation, particularly at the population level (A = 1.38; P = 30.4; H-e = 0.102). By contrast, the level of population differentiation is much higher (F-ST = 0.441) compared to other conifers, and significant differentiation occurs both between regions and between populations within a region. Climate, geologic, and fossil data suggest that historical factors are mainly responsible for the unique population genetic structure in C. argyrophylla. These factors include severe bottleneck and subsequent genetic drift during Quaternary glaciations and habitat deterioration and fragmentation in postglaciation. In addition, reduced gene flow and relatively high rates of inbreeding may be factors that lead to low population variability and marked genetic differentiation among populations. Implications for the development of conservation strategies for this endangered species are discussed on the basis of these findings.