Genetic variation of the endangered Scaevola hainanensis (Goodeniaceae) in the Jiangjun Stream mouth, Taiwan

Scaevola hainanensis Hance is an endangered plant species in Taiwan. Distribution of this species in Taiwan is restricted to 6 connected ditches, which cover an area smaller than 1 ha at the estuary of Jiangjun Stream, Tainan County, southwestern Taiwan. We examined the genetic variation with inter-simple sequence repeat (ISSR) fingerprints. Fifty samples from 6 ditches were collected. In total, 27 primers were used, and 233 bands were obtained, of which only 6 bands (2.58%) were polymorphic, indicating low levels of genetic variation. The analysis of molecular variance (AMOVA) revealed that 93.85% of the variance component was attributable to the variation among individuals within ditches. Low levels of the genetic differentiation coefficient among ditches, G(subscript ST)=0.172 and Nm=2.4, indicated that the ditches barely hinder gene flow between Scaevola populations. UPGMA cluster analysis and principal coordinate analysis revealed no major groupings among ditches or among plants. If the present habitat is damaged, the species will inevitably be confronted with extirpation from Taiwan. Therefore, we suggest that ex situ conservation should be conducted in order to enlarge the population size.