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首页> 外文期刊>International journal of plant sciences >ISOLATING NUCLEAR GENES AND IDENTIFYING LINEAGES WITHOUT MONOPHYLY: AN EXAMPLE OF CLOSELY RELATED SPECIES FROM SOUTHERN MADAGASCAR
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ISOLATING NUCLEAR GENES AND IDENTIFYING LINEAGES WITHOUT MONOPHYLY: AN EXAMPLE OF CLOSELY RELATED SPECIES FROM SOUTHERN MADAGASCAR

机译：分离核基因并无需单眼辨认谱系：来自马达加斯加南部的近缘种的一个例子

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摘要

Megistostegium, a small genus endemic to southern Madagascar, comprises three morphologically distinct species that live in sympatry, lack obvious prezygotic barriers to gene flow, and occasionally hybridize. The genus is one among many plant groups that contain distinct morphological species despite genetic permeability. Such systems are difficult to study because of the need to utilize rapidly evolving nuclear genes, which may be difficult and expensive to isolate. Additionally, analytical methods investigating genealogical patterns at the boundary between the phylogenetic level and the population genetic level are in their nascent stages. As a solution to the first problem, we collected nuclear genotypic data for four loci with the aid of single-stranded conformational polymorphism as a means to isolate alleles from heterozygotes without cloning. As a solution to the second, we used the genealogical sorting index (GSI) and developed a new taxonomic autocorrelation test, both of which can be used to determine how closely predefined species (or geographic areas) approach monophyly. We applied these methods to generate and analyze sequence data for four nuclear loci and plastid DNA from Megistostegium. None of the three traditionally delimited species was monophyletic for any gene. Nonetheless, the GSI and autocorrelation tests detected situations in which the taxonomic species were significantly closer to monophyly than expected under the null hypothesis of no taxonomic structure. These analyses suggest that while phylogenetic signal is confounded by hybridization and perhaps incomplete lineage sorting, the three Megistostegium species have meaningful, if incomplete, genetic distinctiveness.
机译：Megistostegium是马达加斯加南部的特有种，由三个形态学独特的物种组成，它们生活在交配状态，缺乏明显的合子前基因屏障，并偶尔杂交。该属是尽管具有遗传通透性但仍包含独特形态物种的许多植物组之一。由于需要利用迅速发展的核基因，而分离这些核基因可能既困难又昂贵，因此很难研究这类系统。此外，研究系统发育水平和种群遗传水平之间边界的家谱模式的分析方法还处于起步阶段。作为第一个问题的解决方案，我们借助单链构象多态性收集了四个基因座的核基因型数据，以作为无需克隆即可从杂合子中分离等位基因的方法。作为第二种解决方案，我们使用了族谱排序指数（GSI）并开发了一种新的分类学自相关测试，这两种测试都可以用来确定预定义物种（或地理区域）如何单方面接近。我们应用这些方法来生成和分析来自Megistostegium的四个核基因座和质体DNA的序列数据。这三个传统上划界的物种中，没有一个对任何基因而言都是单系的。尽管如此，GSI和自相关检验检测到的情况是，在没有分类结构的无效假设下，分类物种比预期的接近单亲物种。这些分析表明，虽然系统发育信号被杂交甚至是不完整的谱系分类所迷惑，但三种紫背兰属物种具有有意义的（即使不完整的）遗传特征。

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