Laboratorio de Evolución Molecular y Experimental, Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, AP, 70-275 Coyoacán 04510, Ciudad de México, México.
Am J Bot. 2020 Nov;107(11):1542-1554. doi: 10.1002/ajb2.1561. Epub 2020 Nov 17.
Past climate fluctuations during the Holocene and Pleistocene shaped the distribution of several plant species in temperate areas over the world. Wild maize, commonly known as teosinte, is a good system to evaluate the effects of historical climate fluctuations on genetic diversity due to its wide distribution in Mexico with contrasting environmental conditions. We explored the influence of contemporary factors and historical environmental shifts on genetic diversity, including present and three historical periods using neutral markers.
We used 22 nuclear microsatellite loci to examine the genetic diversity of 14 populations of Zea mays subsp. parviglumis and 15 populations of Zea mays subsp. mexicana (527 individuals total). We implemented genetic structure analyses to evaluate genetic differentiation between and within subspecies. We applied coalescent-based demographic analysis and species distribution modeling to evaluate the effects of historical environmental shifts.
We found 355 alleles in total for the two subspecies and variable levels of diversity in each (Z. mays subsp. parviglumis expected heterozygosity H = 0.3646-0.7699; Z. mays subsp. mexicana H = 0.5885-0.7671). We detected significant genetic structure among populations (D = 0.4332) with significant heterozygote deficiency (F = 0.1796), and variable selfing rates (sg = 0.0-0.3090). The Bayesian assignment analysis differentiated four genetic groups. Demographic and species distribution modeling analysis suggested that environmental shifts were influential in the amount of genetic diversity.
Our analyses suggest that the current genetic diversity in teosinte is shaped by factors such as local adaptation and genetic isolation, along with historical environmental fluctuations.
全新世和更新世的过去气候波动塑造了世界温带地区几种植物物种的分布。野生玉米，通常称为类蜀黍，是一个很好的系统，可以评估历史气候波动对遗传多样性的影响，因为它在墨西哥广泛分布，具有截然不同的环境条件。我们使用中性标记物探索了当代因素和历史环境变化对遗传多样性的影响，包括现在和三个历史时期。
我们使用了 22 个核微卫星标记来研究 14 个 Zea mays subsp. parviglumis 种群和 15 个 Zea mays subsp. mexicana 种群（共 527 个个体）的遗传多样性。我们进行了遗传结构分析，以评估亚种间和亚种内的遗传分化。我们应用基于合并的种群动态分析和物种分布模型来评估历史环境变化的影响。
我们在这两个亚种中共发现了 355 个等位基因，每个亚种的多样性水平不同（Z. mays subsp. parviglumis 预期杂合度 H = 0.3646-0.7699；Z. mays subsp. mexicana H = 0.5885-0.7671）。我们在种群间检测到显著的遗传结构（D = 0.4332），存在显著的杂合子缺失（F = 0.1796）和可变的自交率（sg = 0.0-0.3090）。贝叶斯分配分析区分了四个遗传群体。种群动态和物种分布模型分析表明，环境变化对遗传多样性的数量有影响。
我们的分析表明，类蜀黍的当前遗传多样性是由局部适应和遗传隔离等因素以及历史环境波动共同塑造的。
