Genetic diversity of Ottelia acuminata ( Hydrocharitaceae ) from the Eastern Himalayas , revealed by ISSR markers

Ottelia acuminata (Gagnep.) Dandy (Hydrocharitaceae), an endangered aquatic species, was investigated in the Eastern Himalayas, especially in Yunnan Province of Southwest China. The genetic diversity among seven populations was examined using inter-simple sequence repeat (ISSR) amplification markers. The field survey showed that 43.5% natural populations of O. acuminata have become extinct during the last 30 years. Among 13 remaining wild populations, eight (61.5%) are on the edge of extinction and only five (38.5%) were unaffected. For the study on seven populations based on ten primers, 147 clear and reproducible DNA fragments were generated, of which 144 (97.96%) were polymorphic. Within populations, however, the polymorphic bands (PPB) generated by ISSRs was 53 and occupied 36.05% in population B, and similarly within population J (51 and 34.69%, respectively). The results showed that genetic variation is much higher among populations of O. acuminata than within populations. Analyses of Nei’s gene diversity, genetic distance and Shannon’s index also agreed with these results. The average value of Nei’s gene diversity (h) equaled 0.3710. The coefficient of genetic differentiation (Gst) equaled 0.5487, which means that 54.87% of the total molecular variance existed among populations. Such a high level of divergence present among populations may be caused by the complex topography and separated habitats which effectively restrict gene flow. Moreover, there is a lack of significant association between genetic and geographical distances (r = 0.28889, P > 0.05) in the populations of O. acuminata. Therefore, we proposed an appropriate strategy for conserving the genetic resources of O. acuminata in the Eastern Himalayas; namely, rescuing and conserving the core populations in situ, while selecting and preserving more populations with fewer individuals from each population ex situ. Key-words: Ottelia acuminata, genetic diversity, conservation, Eastern Himalayas, Yunnan Plateau, China