Geng Qifang, Wang Zhongsheng, Tao Jianmin, Kimura Megumi K, Liu Hong, Hogetsu Taizo, Lian Chunlan
School of Life Sciences, Nanjing University, Nanjing, China.
Asian Natural Environmental Science Center, The University of Tokyo, Tokyo, Japan.
Front Genet. 2021 Mar 8;12:615911. doi: 10.3389/fgene.2021.615911. eCollection 2021.
Mangrove forest ecosystems, which provide important ecological services for marine environments and human activities, are being destroyed worldwide at an alarming rate. The objective of our study was to use molecular data and analytical techniques to separate the effects of historical and contemporary processes on the distribution of mangroves and patterns of population genetic differentiation. Seven mangrove species (, , , , , , and ), which are predominant along the coastlines of South China, were genotyped at nuclear (nSSR) and chloroplast (cpSSR) microsatellite markers. We estimated historical and contemporary gene flow, the genetic diversity and population structure of seven mangrove species in China. All of these seven species exhibited few haplotypes, low levels of genetic diversity ( = 0.160-0.361, with the exception of ) and high levels of inbreeding ( = 0.104-0.637), which may be due to their marginal geographical distribution, human-driven and natural stressors on habitat loss and fragmentation. The distribution patterns of haplotypes and population genetic structures of seven mangrove species in China suggest historical connectivity between populations over a large geographic area. In contrast, significant genetic differentiation [ = 0.165-0.629 (nSSR); = 0.173-0.923 (cpSSR)] indicates that populations of mangroves are isolated from one another with low levels of contemporary gene flow among populations. Our results suggest that populations of mangroves were historically more widely inter-connected and have recently been isolated, likely through a combination of ocean currents and human activities. In addition, genetic admixture in Beibu Gulf populations and populations surrounding Hainan Island and southern mainland China were attributed to asymmetric gene flow along prevailing oceanic currents in China in historical times. Even ocean currents promote genetic exchanges among mangrove populations, which are still unable to offset the effects of natural and anthropogenic fragmentation. The recent isolation and lack of gene flow among populations of mangroves may affect their long-term survival along the coastlines of South China. Our study enhances the understanding of oceanic currents contributing to population connectivity, and the effects of anthropogenic and natural habitat fragmentation on mangroves, thereby informing future conservation efforts and seascape genetics toward mangroves.
红树林生态系统为海洋环境和人类活动提供重要的生态服务，然而在全球范围内正以惊人的速度遭到破坏。我们研究的目的是利用分子数据和分析技术，区分历史和当代过程对红树林分布及种群遗传分化模式的影响。对在中国南部沿海占主导地位的七种红树林物种（、、、、、、），在核微卫星标记（nSSR）和叶绿体微卫星标记（cpSSR）上进行基因分型。我们估计了中国七种红树林物种的历史和当代基因流、遗传多样性及种群结构。这七种物种均表现出单倍型数量少、遗传多样性水平低（= 0.160 - 0.361，除外）以及近亲繁殖程度高（= 0.104 - 0.637）的情况，这可能归因于它们边缘的地理分布、人类活动以及栖息地丧失和破碎化带来的自然压力源。中国七种红树林物种的单倍型分布模式和种群遗传结构表明，在较大地理区域内种群之间存在历史上的连通性。相比之下，显著的遗传分化[= 0.165 - 0.629（nSSR）；= 0.173 - 0.923（cpSSR）]表明，红树林种群彼此隔离，种群间当代基因流水平较低。我们的研究结果表明，红树林种群在历史上联系更为广泛，近期才被隔离，可能是洋流和人类活动共同作用的结果。此外，北部湾种群以及海南岛和中国大陆南部周边种群的遗传混合归因于历史时期中国沿盛行洋流的不对称基因流。即使洋流促进了红树林种群间的基因交流，仍无法抵消自然和人为破碎化的影响。近期红树林种群的隔离和缺乏基因流可能会影响它们在中国南部沿海的长期生存。我们的研究增进了对洋流促进种群连通性的理解，以及人为和自然栖息地破碎化对红树林的影响，从而为未来红树林的保护工作和景观遗传学提供参考。
