Magnolias are characteristic tree species of the Tropical Montane Cloud Forest (TMCF) in Mexico, an ecosystem that is highly threatened by habitat fragmentation and climate change. In this study, based on DNA sequences from five regions (chloroplast: trnT-trnL, trnK5-matK, trnS-trnG, rpl32-trnL, nuclear: ITS) and seven nuclear microsatellite markers, we aimed to delineate species boundaries between two-endemic species of the TMCF, Magnolia pedrazae and Magnolia schiedeana, and to estimate levels of genetic structure and diversity among populations. Phylogenetic and haplotype network analyses for the chloroplast and ITS regions did not support genetic differentiation as two distinctive species. Results from Bayesian and multivariate cluster analyses based on microsatellite loci showed high genetic differentiation across most populations, which was consistent with a strong and significant pattern of isolation by geographical distance. We found moderate to high levels of population genetic diversity, but it was lower in small populations relative to large populations. Our results suggest a contemporary decrease of genetic connectivity among populations, likely as a consequence of the current decline of suitable TMCF habitat. Managing landscape connectivity among remnant Magnolia populations within protected natural parks and surroundings, and with emphasis of small populations, would be key for the species conservation.

中文翻译：

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墨西哥两种地方性木兰种（木兰科；木兰科）的物种定界和遗传结构

木兰是墨西哥热带山地云雾林 (TMCF) 的特色树种，该生态系统受到栖息地破碎化和气候变化的高度威胁。在这项研究中，基于来自五个区域（叶绿体：trnT-trnL、trnK5-matK、trnS-trnG、rpl32-trnL、核：ITS）的 DNA 序列和七个核微卫星标记，我们旨在划定两个地方性流行病之间的物种界限。 TMCF、Magnolia pedrazae 和 Magnolia schiedeana 的物种，并估计种群之间的遗传结构和多样性水平。叶绿体和 ITS 区域的系统发育和单倍型网络分析不支持作为两个独特物种的遗传分化。基于微卫星位点的贝叶斯和多元聚类分析的结果显示，大多数种群的遗传分化程度很高，这与地理距离造成的强烈而显着的隔离模式是一致的。我们发现了中等至高水平的群体遗传多样性，但相对于大群体，小群体的遗传多样性较低。我们的结果表明，当代种群之间的遗传连通性下降，这可能是目前合适的 TMCF 栖息地减少的结果。在受保护的自然公园和周围环境中，以小种群为重点，管理残余木兰种群之间的景观连通性，将是物种保护的关键。我们的结果表明，当代种群之间的遗传连通性下降，这可能是目前合适的 TMCF 栖息地减少的结果。在受保护的自然公园和周围环境中，以小种群为重点，管理残余木兰种群之间的景观连通性，将是物种保护的关键。我们的结果表明，当代种群之间的遗传连通性下降，这可能是目前合适的 TMCF 栖息地减少的结果。在受保护的自然公园和周围环境中，以小种群为重点，管理残余木兰种群之间的景观连通性，将是物种保护的关键。