Red de Biodiversidad y Sistemática, Centro Regional de Bajío, Instituto de Ecología AC, Pátzcuaro, Michoacán, Mexico.
Departments of Plant and Microbial Biology and Integrative Biology and the University and Jepson Herbaria, University of California, Berkeley, Berkeley, California, United States of America.
PLoS One. 2014 Jun 6;9(6):e98754. doi: 10.1371/journal.pone.0098754. eCollection 2014.
The hypothesis of ecological speciation states that as populations diverge in different niches, reproductive isolation evolves as a by-product of adaptation to these different environments. In this context, we used Nolina parviflora as a model to test if this species evolved via ecological speciation and to explore current and historical gene flow among its populations. Nolina parviflora is a montane species endemic to Mexico with its geographical distribution restricted largely to the Trans-Mexican Volcanic Belt. This mountain range is one of the most complex geological regions in Mexico, having undergone volcanism from the mid-Miocene to the present. Ecologically, the Trans-Mexican Volcanic Belt possesses different types of vegetation, including tropical dry forest; oak, pine, pine-oak, and pine-juniper forests; and xerophytic scrub--all of which maintain populations of N. parviflora. Using species distribution models, climatic analyses, spatial connectivity and morphological comparisons, we found significant differences in climatic and morphological variables between populations of N. parviflora in two distinct Trans-Mexican Volcanic Belt regions (east vs. west). This could mean that the geographically isolated populations diverged from one another via niche divergence, indicating ecological speciation. Spatial connectivity analysis revealed no connectivity between these regions under the present or last glacial maximum climate models, indicating a lack of gene flow between the populations of the two regions. The results imply that these populations may encompass more than a single species.
生态物种形成假说认为，随着种群在不同的生态位上分化，生殖隔离作为适应这些不同环境的副产品而进化。在这种情况下，我们使用多丽花作为模型来检验该物种是否通过生态物种形成进化而来，并探索其种群之间当前和历史上的基因流。多丽花是一种山地物种，分布于墨西哥，其地理分布主要局限于跨墨西哥火山带。这条山脉是墨西哥最复杂的地质区域之一，从中新世中期到现在一直经历着火山活动。在生态上，跨墨西哥火山带拥有不同类型的植被，包括热带干旱森林；橡木、松树、松-橡木和松-杜松林；以及旱生灌丛——所有这些都维持着多丽花的种群。通过物种分布模型、气候分析、空间连通性和形态比较，我们发现分布在两个不同的跨墨西哥火山带地区（东和西）的多丽花种群在气候和形态变量方面存在显著差异。这可能意味着地理上隔离的种群通过生态位的分歧而彼此分化，表明发生了生态物种形成。空间连通性分析表明，在当前或末次冰期气候模型下，这些地区之间没有连通性，表明这两个地区的种群之间没有基因流。结果表明，这些种群可能包含不止一个物种。
