Data from: Complex phylogeographic patterns indicate Central American origin of two widespread Mesoamerican Quercus (Fagaceae) species

The northern Neotropical region is characterized by a heterogeneous
geological and climatic history. Recent studies have shown contrasting
patterns regarding the role of geographic elements as barriers that could
have determined phylogeographic structure in various species. Recently,
the phylogeography and biogeography of Quercus species have been studied
intensively, and the patterns observed so far suggest contrasting
evolutionary histories for Neotropical species in comparison with their
Holarctic relatives. The goal of this study was to describe the
phylogeographic structure of two Neotropical oak species (Quercus insignis
and Quercus sapotifolia) in the context of the geological and
palaeoclimatic history of the northern Neotropics. Populations through the
distribution range of both species were collected and characterized using
nine chloroplast DNA microsatellite loci. Both oak species showed high
levels of genetic diversity and strong phylogeographic structure. The
distribution of genetic variation in Q. insignis suggested an influence of
two major barriers, the Isthmus of Tehuantepec and the Nicaraguan
Depression, while Q. sapotifolia exhibited a genetic structure defined by
the heterogeneity of the Chortis highlands. The haplotype networks of both
species indicated complex histories, suggesting that colonization from the
Sierra Madre de Chiapas to central Mexico and from the north of the
Nicaraguan Depression to the Costa Rican mountains may have occurred
during different stages, and apparently more than one time. In conclusion,
the phylogeographic structure of Neotropical oak species seems to be
defined by a combination of geological and climatic events.

新热带北部区域（Northern Neotropical Region）以非均一的地质与气候演化历史为显著特征。已有研究表明，地理要素作为可能决定不同物种种群谱系地理结构（phylogeographic structure）的屏障，其作用模式存在显著差异。近年来，栎属（Quercus）物种的谱系地理学（phylogeography）与生物地理学（biogeography）已得到深入研究，目前观测到的分布模式显示，新热带栎类与其全北区（Holarctic）近缘类群的演化历史存在显著分歧。本研究旨在结合新热带北部区域的地质与古气候历史，阐明两种新热带栎类——显脉栎（Quercus insignis）与山榄叶栎（Quercus sapotifolia）的谱系地理结构。研究人员采集了两个物种分布范围内的所有种群，并利用9个叶绿体DNA微卫星位点（chloroplast DNA microsatellite loci）对其进行遗传特征解析。两种栎类均表现出较高的遗传多样性水平与极强的谱系地理结构。显脉栎（Q. insignis）的遗传变异分布模式表明，特万特佩克地峡（Isthmus of Tehuantepec）与尼加拉瓜凹陷（Nicaraguan Depression）这两大地理屏障对其种群分化产生了显著影响；而山榄叶栎（Q. sapotifolia）的遗传结构则由乔蒂斯高地（Chortis highlands）的非均一性所塑造。两种栎类的单倍型网络（haplotype networks）均揭示出复杂的演化历史，暗示其种群曾经历多阶段、多次的扩散事件：从恰帕斯马德雷山脉（Sierra Madre de Chiapas）向墨西哥中部的扩散，以及从尼加拉瓜凹陷北部向哥斯达黎加山地的扩散。综上，新热带栎类的谱系地理结构似乎是地质与气候事件共同作用的结果。