High ISSR variation in 24 surviving individuals of Apterosperma oblata (Theaceae) endemic to China

Apterosperma oblata is a critically endangered Theaceous species endemic to southern China, with only 24 individuals surviving in Ba Jia Zhen, Yangchun, Guangdong province. ISSR markers were used to assess their genetic variation and relationships. Population genetic parameters were estimated by a Bayesian approach as well as conventional methods. Twenty-one primers generated 168 loci, of which 130 (77.38%) were polymorphic. Nei's gene diversity, Shannon's index, and average expected heterozygosity were quantified as 0.2746, 0.4100, and 0.3492, respectively. Compared with other species of Theaceae and its related families, a high level of genetic variation was identified in A. oblata. Cluster analysis using the unweighted pair-group method with arithmetic mean (UPGMA) showed that the 24 individuals mainly fell into three groups of which the grouping of individuals BJZ21, BJZ22, BJZ23, and BJZ24 and their genetic isolation were supported by a principle components analysis (PCA). In addition, molecular bottleneck signatures were revealed in recent population history. In terms of these results, the management and conservation strategy of A. oblata was proposed.