Low genetic diversity and small effective population size in the endangered Hopea reticulata (Dipterocarpaceae) on Hainan Island, China

Abstract

Hopea reticulata Tardieu (Dipterocarpaceae) represents a critically endangered tree species primarily confined to the Ganza Ridge of Hainan Island, China, with a couple of additional records of populations in Thailand and Vietnam. Neither the species’ genetic diversity, which is essential for a species’ long-term survival in the face of changing climate and various biotic stresses, nor the demographic history, which directly affects genetic diversity, has been examined. In this study, we employed double-digest restriction site-associated sequencing to investigate the population structure and evolutionary history of H. reticulata on Hainan Island. Our analysis revealed that H. reticulata exhibits the lowest nucleotide diversity (π = 0.00091) when compared to other well-known endangered tree species in China that have been assessed using high-throughput sequencing data. Utilizing the software Stairway Plot 2 for demographic history inference, we identified a significant reduction in effective population size of H. reticulata, a result concordant with the species’ restricted geographic range and likely responsible for its low genetic diversity. Additionally, our research unveiled a weak genetic structure within geographically close H. reticulata populations, probably resulted from limited seed dispersal. These findings offer valuable insights into the conservation and management strategies required for the protection of H. reticulata on Hainan Island.

Keywords

• Double-digest restriction site-associated sequencing (ddRAD-Seq)
• Genetic diversity
• Population decline
• Hopea reticulata Tardieu
• Lowland rainforest