Acorn weevils critically impact forest regeneration in semi-humid evergreen broad-leaved forests (SEBFs) by parasitizing and consuming acorns before dispersal. Despite their ecological significance, research on the species diversity of acorn weevils within SEBFs remains limited. To address this gap, we assessed the species diversity and host affinity of acorn weevils across six dominant oak species at 18 locations. We performed DNA extraction and mitochondrial COI gene sequencing on weevil larvae and analyzed acorn functional traits (AFTs) from host acorns. Six acorn weevil species across four genera and two families were identified within the dominant acorns of SEBFs. Curculio dentipes showed the lowest host specificity, while Niphades castanea and Cyllorhynchites ursulus were specialist species. Notably, the species diversity of acorn weevils was significantly lower in Quercus franchetii than in others. Acorn volume and three secondary metabolite contents, including total phenols, total flavonoids, and tannins, were the primary AFTs influencing weevil species diversity. This study not only advances our comprehension of acorn weevil species diversity and their ecological interactions with oak hosts, but also provides valuable insights for the ecological management of SEBFs in southwest China.

Climate change is altering the geographical distribution and abundance of species. Abundant genetic variation generally indicates a stronger adaptability and evolutionary potentiality, especially in case of sharply changing climates or environments. With the past global climate fluctuations, especially the climate oscillation since the Quaternary, the global temperature changes related to glaciation, many relict plant species have formed possible refugia in humid subtropical/warm temperate forests, thus retaining a high level of genetic diversity patterns. Based on the contraction and expansion of the geographical distribution of Taxus wallichiana Zucc. in the past driven by climate change, combined with the contemporary genetic diversity modeling, the distribution performance of Taxus wallichiana Zucc. in future climate change was predicted. The areas of highly suitable habitat will increase with climate change in the future. There were continuous and stable high suitable areas of T. wallichiana in the southeastern Tibet and northwestern Yunnan as long-term stable climate refugia. We made the genetic landscape surface of T. wallichiana complex and discovered geographical barriers against gene flow. Genetic barriers spatially isolated the center of genetic diversity into three regions: west (east Himalaya), middle (Yunnan plateau, Sichuan basin, Shennongjia, and the junction of Guizhou and Guangxi provinces), and east (Mt. Huangshan and Fujian). Southern Tibet was isolated from other populations. The central and western Yunnan, the Sichuan basin, and surrounding mountains were isolated from the southern China populations. We found that the positive correlationships between the present species genetic diversity and suitability index during LGM, MH, and 2070. This infers that T. wallichiana has provisioned certain genetic diversity and has strong evolutionary potential under conditions of climate change.