State Key Laboratory of Biocontrol and Guangdong Provincial Key Laboratory of Plant Resources, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, Guangdong, China.
Department of Bioengineering, Zhuhai Campus of Zunyi Medical University, Zhuhai, 519041, Guangdong, China.
Planta. 2021 Nov 29;255(1):7. doi: 10.1007/s00425-021-03798-8.
This study identified the historical geoclimatic factors which caused low genetic diversity and strong phylogeographic structure in a cryptoviviparous mangrove. The phylogeographic pattern was used to suggest conservation actions. Phylogeographic studies are used to understand the spatial distribution and evolution of genetic diversity, and have major conservation implications, especially for threatened taxa like the mangroves. This study aimed to assess the phylogeographic pattern of Aegiceras corniculatum, a cryptoviviparous mangrove, across its distribution range in the Indo-West Pacific (IWP) region. We genotyped 398 samples, collected from 37 populations, at four chloroplast DNA (cpDNA) loci, and identified the influence of historical processes on the contemporary population structure of the species. Low genetic diversity at the population level was observed. The evolutionary relationship between 12 cpDNA haplotypes suggested a strong phylogeographic structure, which was further validated by the clustering algorithms and proportioning of maximum variation among hierarchical population groups. The magnitude and direction of historical gene flow indicated that the species attained its wide distribution from its likely ancestral area of the Malay Archipelago. The divergence time estimates of the haplotypes indicated that the geoclimatic changes during the Pleistocene, especially the glacial sea-level changes and emergence of landmasses, hindered genetic exchange and created genetic differentiation between the phylogenetic groups. The species overwintered the last glacial maxima in multiple refugia in the IWP, as identified by the environmental niche modelling. Overall, our findings indicated that ancient glacial vicariance had influenced the present genetic composition of A. corniculatum, which was maintained by the current demographic features of this region. We discussed how these findings can be used to prioritize areas for conservation actions, restore disturbed habitats and prevent further genetic erosion.
本研究确定了导致隐胎生红树林遗传多样性低和系统地理结构强的历史地理气候因素。系统地理格局被用来提出保护措施。系统地理研究用于了解遗传多样性的空间分布和演化，对保护具有重要意义，特别是对红树林等受威胁的类群。本研究旨在评估隐胎生红树林桐花树在印度洋-西太平洋（IWP）地区的分布范围内的系统地理格局。我们在四个叶绿体 DNA（cpDNA）基因座上对 398 个样本进行了基因型分析，这些样本来自 37 个种群，并确定了历史进程对该物种当代种群结构的影响。在种群水平上观察到遗传多样性较低。12 个 cpDNA 单倍型的进化关系表明存在强烈的系统地理结构，聚类算法和分层种群群体之间最大变异的比例进一步验证了这一点。历史基因流的幅度和方向表明，该物种从马来群岛的可能祖先地区获得了广泛的分布。单倍型的分歧时间估计表明，更新世的地理气候变化，特别是冰川海平面变化和陆地的出现，阻碍了遗传交换，导致了系统地理群体之间的遗传分化。该物种在 IWP 的多个避难所中度过了最后一次冰川高峰期，这是通过环境生态位模型确定的。总的来说，我们的研究结果表明，古代冰川的隔离作用影响了桐花树的现代遗传组成，而当前该地区的人口特征则维持了这种遗传组成。我们讨论了如何利用这些发现来确定保护行动的优先领域，恢复受干扰的栖息地，并防止进一步的遗传侵蚀。
