Kobayashi Yukihiro, Komaki Yoshiteru, Isagi Yuji
Graduate School of Agriculture, Kyoto University, Kyoto, Japan.
Botanical Gardens, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
Sci Rep. 2024 Jul 17;14(1):15668. doi: 10.1038/s41598-024-65726-6.
Melastoma (Melastomataceae) includes ca. 100 species across tropical to subtropical regions of Asia and Oceania. The Bonin Islands harbor three endemic taxa: M. tetramerum, M. tetramerum var. pentapetalum, and M. candidum var. alessandrense. Of these, M. tetramerum is critically endangered and faces near extinction in the wild. This study investigates the phylogenetic relationships among these endemic Melastoma species in the Bonin Islands based on the whole chloroplast genome and nuclear SNPs. The results revealed that M. candidum var. alessandrense was placed in the clade of the widespread East Asian M. candidum and has a distinct evolutionary origin from the other two taxa. The population genomics analyses (heterozygosity, rates of deleterious mutations, and numbers and lengths of runs of homozygosity) indicated lower genetic diversity and more vulnerable genomes of endemic Melastoma, especially M. tetramerum var. pentapetalum. M. tetramerum var. pentapetalum is not a target of any protection programs, however, conservation plans might be required for this variety because M. tetramerum var. pentapetalum would have a more vulnerable genome than M. tetramerum, which faces near extinction in the wild. This information can facilitate the development of effective conservation strategies in a precautionary way that anticipates imminent threats to the survival of the species.
野牡丹属（野牡丹科）包括约100个物种，分布于亚洲和大洋洲的热带至亚热带地区。小笠原群岛有三种特有分类群：四方野牡丹、四方野牡丹五瓣变种和白花野牡丹亚历山德里变种。其中，四方野牡丹极度濒危，在野外面临近乎灭绝的境地。本研究基于整个叶绿体基因组和核单核苷酸多态性，调查了小笠原群岛这些特有野牡丹属物种之间的系统发育关系。结果表明，白花野牡丹亚历山德里变种被置于广泛分布的东亚白花野牡丹分支中，与其他两个分类群有不同的进化起源。群体基因组学分析（杂合度、有害突变率以及纯合子片段的数量和长度）表明，特有野牡丹属的遗传多样性较低，基因组更易受影响，尤其是四方野牡丹五瓣变种。然而，四方野牡丹五瓣变种并非任何保护计划的目标，但可能需要为该变种制定保护计划，因为四方野牡丹五瓣变种的基因组比在野外面临近乎灭绝的四方野牡丹更易受影响。这些信息有助于以预防的方式制定有效的保护策略，预见对物种生存的紧迫威胁。
