Genetic diversity and structure analysis of the endangered plant species Horsfieldia hainanensis Merr. in China

The genetic diversity and structure of nine natural populations of Horsfieldia hainanensis Merr., an endangered plant endemic to China, were studied using inter-simple sequence repeat markers. Nine primers were selected from 100 primers to evaluate 126 individual plants, from which a total of 136 bands were amplified and 108 bands were polymorphic. Our results demonstrated that the genetic diversity level of H. hainanensis was high with a percentage of polymorphic bands, Shannon's diversity index and Nei's genetic diversity index at the species level of 79.4%, 0.4787 and 0.3314, respectively, and correspondingly, averages of 40.4%, 0.2615 and 0.1843 at the population level. Significant genetic differentiation was observed among populations, showing that the coefficient of genetic differentiation among populations calculated using Nei's genetic diversity was 0.4509. The ranges of Nei's genetic identity and genetic distance among populations were 0.7387-0.8637 and 0.1466-0.3029, respectively. The unweighted pair group method with arithmetic mean clustering based on Nei's genetic distance indicated that nine natural H. hainanensis populations could be classified into two lineages. Collectively, we speculated that habitat fragmentation and disturbance from human activities could be considered the main reasons for the endangerment of H. hainanensis, and we propose in situ conservation for the existing natural H. hainanensis populations, especially at Mengtun, Niandou and Tongbiguan, where the genetic diversity is relatively high.