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

## TL;DR

This study explores the reproductive biology and genetic diversity of the endangered mangrove species Sonneratia ovata to support its conservation and management.

## Contribution

This is the first study to investigate the reproductive traits, genetic diversity, and population structure of Sonneratia ovata using SSR markers.

## Key findings

- Sonneratia ovata has a mixed mating system and requires pollinators despite being partially self-compatible.
- The species exhibits low genetic diversity (He = 0.215) with most genetic variation occurring within populations.
- Geographic and genetic distances among populations are positively correlated, following the IBD model.

## Abstract

Sonneratia ovata is a mangrove species with important ornamental, economic, ecological, and medicinal value that is listed as an endangered species. However, there are few studies on the reproductive traits, genetic diversity, and population structure of S. ovata. People could not accurately understand its genetic background and reproductive status, and therefore could not conserve and manage it better. In order to understand the genetic background and reproductive status of S. ovata, pertinent studies were carried out through pollination, mating system, and SSR method. 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. The genetic diversity (He = 0.215) of populations was low, 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 (r2 = 0.4841 p = 0.05) among populations, which was in line with the IBD model. Molecular variance mainly existed within populations (75.4%), while only 24.6% existed among populations (p < 0.001). 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.

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 (He = 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.