Reproductive Biology and Population Structure of the Endangered Species Sonneratia ovata Backer

Sonneratia ovata is an important tree species for ornamental, economic, ecological, and medicinal value and is identified as an endangered species. There are very few studies on the reproductive traits, genetic diversity, and population structure of S. ovata. Therefore, it is urgent to accurately understand its genetic background and reproductive status in order to better conserve and manage S. ovata. S. ovata has a mixed mating system, is partially self-compatible and needs pollinators, according to the outcrossing index, pollen-ovule ratio, pollination treatment results and outcrossing rate. Natural populations maintained high outcrossing coupled with inbreeding and low genetic diversity (H_e = 0.215), and the population DC was regarded as the center of genetic diversity. The Mantel test showed that there existed a positive correlation between geographic and genetic distance among populations, which was in line with the IBD model. Molecular variance was largely confined to within-population differences (75.4%), while inter-population differences accounted for 24.6%. Structure and PCoA analysis supported the UPGMA cluster. This study is the first to investigate reproductive traits, genetic diversity, and population structure through SSR. The results provide a scientific basis for cross breeding, conservation, and management of this species. In future, it is necessary to increase relevant research (human, environment, habitat factors, etc.) to better protect and utilize this species.