Departamento de Biología de la Conservación, Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE), Ensenada, Baja California, México.
Departamento de Genética, Microbiología y Estadística, Universidad de Barcelona (UB), Barcelona, Catalonia, Spain.
Plant Biol (Stuttg). 2022 Jan;24(1):185-191. doi: 10.1111/plb.13346. Epub 2021 Oct 11.
Endemic species distributed in fragmented habitats are highly vulnerable to extinction because they may have low genetic diversity. However, some life-history traits can mitigate the effect of genetic drift on populations. We analysed the level and distribution of genetic variation and ancestral population size of Yucca capensis, a long-lived endemic plant of the Baja California Peninsula, Mexico. Its populations are scattered across a habitat that is suffering accelerated transformation. We used six nuclear microsatellites to genotype 224 individuals from 17 locations across the entire species' geographic range. We estimated polymorphisms, heterozygosity and genetic structure. We also evaluated the ancestral and recent effective size and time since the population started to change. We found high heterozygosity, high polymorphism and low differentiation among locations, suggesting a panmictic population across the range. We also detected a large ancestral effective population size, which suffered a strong reduction in the Mid-Holocene. Despite changes in environmental conditions caused by habitat modification, the high diversity and low differentiation in Y. capensis may result from its large ancestral effective size and life-history traits, such as plant longevity, clonal growth and mating system, which reduce the rate of loss of genetic variation. However, the dependence on a specialist pollinator that displays short flight range can reduce gene flow among the plant populations and could, shortly, lead them into an extinction vortex.
分布在破碎生境中的特有物种极易灭绝，因为它们可能具有较低的遗传多样性。然而，一些生活史特征可以减轻遗传漂变对种群的影响。我们分析了墨西哥下加利福尼亚半岛特有长寿命植物丝兰的遗传变异水平和分布以及其祖先种群规模。其种群分散在一个加速转化的栖息地中。我们使用 6 个核微卫星对来自整个物种地理范围 17 个地点的 224 个个体进行基因分型。我们估计了多态性、杂合度和遗传结构。我们还评估了祖先和近期有效种群规模以及种群开始变化的时间。我们发现地点之间存在高度的杂合性、高度的多态性和低分化，表明整个范围内存在泛种群。我们还检测到一个较大的祖先有效种群规模，该规模在中全新世经历了强烈的减少。尽管由于栖息地的改变导致环境条件发生了变化，但 Y. capensis 的高多样性和低分化可能是由于其较大的祖先有效种群规模和生活史特征，如植物长寿、无性繁殖和交配系统，这些特征降低了遗传变异的丧失率。然而，对具有短飞行范围的专门传粉者的依赖会减少植物种群之间的基因流动，并可能很快使它们陷入灭绝漩涡。
