Conservation Significance of the Rare and Endangered Tree Species, Trigonobalanus doichangensis (Fagaceae)

Trigonobalanus doichangensis is a rare and endangered species with important evolutionary value and extremely small populations. We investigated the genetic diversity of T. doichangensis to provide information on its effective preservation. We used genotyping-by-sequencing (GBS) technology to assess the genetic diversity, genetic structure and gene flow of the six populations of T. doichangensis. Analysis of SNPs indicated that there was high genetic diversity in the ML and XSBN populations of T. doichangensis. FST values showed moderate genetic differentiation among the populations of T. doichangensis. Meanwhile, admixture, principal components and gene flow analyses indicated that the populations of T. doichangensis are not genetically separated in accordance with their geographical distributions. Habitat destruction and excessive exploitation may have led to a low gene flow, which has in turn resulted in the differences in seed and seedling morphological traits among populations. Based on these findings, we recommend that T. doichangensis be conserved through in situ approaches and artificial seedlings, including preservation of each extant population. Particularly, the ML and XSBN populations have high diversity and more ancestral information, so these two populations should be considered as conservation priorities, and seeds should be collected to obtain germplasm and increase the genetic diversity.