Departamento de Biología Evolutiva, Instituto de Ecología, AC, Carretera antigua a Coatepec No. 351, El Haya, Xalapa, Veracruz, 91070, Mexico.
Departamento de Botánica, Instituto de Biología, Universidad Nacional Autónoma de México, Tercer Circuito s/n, Ciudad Universitaria, Coyoacán, Ciudad de Mexico, 04510, Mexico.
Sci Rep. 2018 Apr 3;8(1):5591. doi: 10.1038/s41598-018-23707-6.
Host specialization after host shifting is traditionally viewed as the pathway to speciation in parasitic plants. However, geographical and environmental changes can also influence parasite speciation, through hybridization processes. Here we investigated the impact of past climatic fluctuations, environment, and host shifts on the genetic structure and patterns of hybridization and gene flow between Psittacanthus calyculatus and P. schiedeanus, a Mesoamerican species complex. Using microsatellites (408 individuals), we document moderate genetic diversity but high genetic differentiation between widespread parental clusters, calyculatus in dry pine-oak forests and schiedeanus in cloud forests. Bayesian analyses identified a third cluster, with admixture between parental clusters in areas of xeric and tropical dry forests and high levels of migration rates following secondary contact. Coincidently host associations in these areas differ from those in areas of parental species, suggesting that past hybridization played a role in environmental and host shifts. Overall, the observed genetic and geographic patterns suggest that these Psittacanthus populations could have entered a distinct evolutionary pathway. The results provide evidence for highlights on the importance of the Pleistocene climate changes, habitat differences, and potential host shifts in the evolutionary history of Neotropical mistletoes.
寄生植物的物种形成过程通常被认为是宿主转移后的宿主专化，但地理和环境变化也可以通过杂交过程影响寄生虫的物种形成。在这里，我们研究了过去气候波动、环境和宿主转移对 Psittacanthus calyculatus 和 P. schiedeanus 之间遗传结构和杂交及基因流模式的影响，Psittacanthus calyculatus 和 P. schiedeanus 是中美洲物种复合体。我们使用微卫星（408 个个体）记录了广泛的亲本群之间适度的遗传多样性，但遗传分化程度很高，calyculatus 存在于干燥的松栎森林中，schiedeanus 存在于云雾森林中。贝叶斯分析确定了第三个聚类，在干旱和热带干燥森林地区存在亲本聚类的混合，并且在二次接触后存在高水平的迁移率。巧合的是，这些地区的宿主联系与亲本物种地区的宿主联系不同，表明过去的杂交在环境和宿主转移中发挥了作用。总的来说，观察到的遗传和地理模式表明，这些 Psittacanthus 种群可能已经进入了一个独特的进化途径。研究结果为强调更新世气候变化、栖息地差异以及潜在的新热带寄生植物的宿主转移在其进化历史中的重要性提供了证据。
