Study On Genetic Diversity Of Dipteronia Dyerana (Sapindaceae): Implications For Conservation

Dipteronia dyeran Henry is a rare endemic from south-eastern Yunnan Province (China) and known from only five natural populations, two of which occur outside a nature reserve. In order to obtain base-line information for the population dynamics, history and conservation of the species we investigated patterns of genetic diversity within and among all natural populations, in addition to an ex situ conserved population, using inter-simple sequence repeat (ISSR) DNA markers. Across all natural populations surveyed, average within-population diversity was remarkably low (e.g., 0.0898 for Nei's gene diversity), with populations from outside the nature reserve maintaining the highest amounts of genetic diversity. Among all natural populations, a high level of genetic differentiation (G_st = 0.375) was detected, together with an isolation-by-distance pattern. Past habitat fragmentation, restricted gene flow and, to a lesser extent, genetic drift are proposed to be the determinant factors responsible for the low genetic diversity and high genetic differentiation observed, although reproductive-ecological factors, such as low seedling recruitment due to inbreeding, might also play a role. We strongly recommend in situ conservation attention to those D. dyerana populations presently occurring outside the nature reserve, as they contain the highest proportion of the species' total ISSR fragment diversity and the largest number of 'private' fragments, which might be eventually relevant for local adaptation. Our data further indicate that the ex situ conserved population only insufficiently represents the genetic diversity present in the species. It is therefore suggested to sample at least four natural populations to cover a reasonable proportion (= 95%) of the species' genetic variation for ex situ conservation.