Population Survey Combined with Genomic-Wide Genetic Variation Unravels the Endangered Status of <i>Quercus gilva</i>

Since the Anthropocene, biodiversity loss owing to human activity and climate change has worsened. <i>Quercus gilva</i> is an evergreen oak species native to China, Japan, and South Korea and is threatened by a long history of human impact. The purpose of this study was to (1) reassess the threatened category of <i>Q. gilva</i> based on a detailed survey, and (2) identify the genetic structure and diversity of <i>Q. gilva</i> based on genomic data. First, we conducted a detailed survey of the populations in China. Second, we collated all the literature and information. Finally, genome-wide genetic variation was analyzed based on 65 individuals from 22 populations. We found that <i>Q. gilva</i> has suffered rapid population decline, and at present, most populations are very small. The evolutionary path of <i>Q. gilva</i> was from the southwest to east of China and then to Japan and South Korea. <i>Quercus gilva</i> showed no distinct genetic structure and had a relatively low genetic diversity. Among the 22 populations, most populations in southwestern China, South Korea, and Japan had high genetic diversity. The populations in Jingning (Zhejiang province; ZJN), Wuyuan (Jinaxi province; JWY), and Zherong (Fujian province; FZR) suffered a strong bottleneck. In conclusion, <i>Q. gilva</i> is an endangered species native to East Asia. Because of the very low genetic diversity of <i>Q. gilva</i> and most populations are small, we need to (1) strengthen the protection of this species, (2) conduct conservation actions with <i>in-situ</i> reinforcement populations, and (3) select populations with high genetic diversity as provenances for afforestation efforts. Finally, we suggest that in the future, genetic diversity should be considered as the sixth criterion for IUCN to evaluate the threatened category.