Auburn University Museum of Natural History, Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA.
Department of Biology, Millsaps College, Jackson, MS 39210, USA.
Mol Phylogenet Evol. 2014 Feb;71:79-93. doi: 10.1016/j.ympev.2013.11.007. Epub 2013 Nov 23.
The North American tarantula genus Aphonopelma provides one of the greatest challenges to species delimitation and downstream identification in spiders because traditional morphological characters appear ineffective for evaluating limits of intra- and interspecific variation in the group. We evaluated the efficacy of numerous molecular-based approaches to species delimitation within Aphonopelma based upon the most extensive sampling of theraphosids to date, while also investigating the sensitivity of randomized taxon sampling on the reproducibility of species boundaries. Mitochondrial DNA (cytochrome c oxidase subunit I) sequences were sampled from 682 specimens spanning the genetic, taxonomic, and geographic breadth of the genus within the United States. The effects of random taxon sampling compared traditional Neighbor-Joining with three modern quantitative species delimitation approaches (ABGD, P ID(Liberal), and GMYC). Our findings reveal remarkable consistency and congruence across various approaches and sampling regimes, while highlighting highly divergent outcomes in GMYC. Our investigation allowed us to integrate methodologies into an efficient, consistent, and more effective general methodological workflow for estimating species boundaries within the mygalomorph spider genus Aphonopelma. Taken alone, these approaches are not particularly useful - especially in the absence of prior knowledge of the focal taxa. Only through the incorporation of multiple lines of evidence, employed in a hypothesis-testing framework, can the identification and delimitation of confident species boundaries be determined. A key point in studying closely related species, and perhaps one of the most important aspects of DNA barcoding, is to combine a sampling strategy that broadly identifies the extent of genetic diversity across the distributions of the species of interest and incorporates previous knowledge into the "species equation" (morphology, molecules, and natural history).
北美的 Aphonopelma 属蜘蛛在种的划分和下游鉴定方面带来了巨大的挑战，因为传统的形态特征对于评估该属内种内和种间变异的极限似乎没有效果。我们评估了基于迄今为止对狼蛛科最广泛采样的多种基于分子的 Aphonopelma 种界定方法的有效性，同时还调查了随机分类群采样对物种边界重现性的敏感性。从美国范围内的属内遗传、分类和地理广度的 682 个标本中采集了线粒体 DNA（细胞色素 c 氧化酶亚基 I）序列。随机分类群采样的影响与传统的邻接法进行了比较，同时还比较了三种现代定量物种界定方法（ABGD、P ID（宽松）和 GMYC）。我们的研究结果揭示了各种方法和采样方案之间的惊人一致性和一致性，同时突出了 GMYC 中高度分歧的结果。我们的调查使我们能够将方法整合到一个高效、一致和更有效的方法学工作流程中，用于估计 Aphonopelma 狼蛛属内的物种边界。单独来看，这些方法并不是特别有用-尤其是在缺乏对焦点类群的先验知识的情况下。只有通过整合多种证据，并在假设检验框架下使用，才能确定确定有信心的物种边界的识别和划分。研究密切相关的物种的一个关键点，也许是 DNA 条形码最重要的方面之一，是结合一种采样策略，该策略广泛识别出感兴趣物种分布范围内的遗传多样性范围，并将先前的知识纳入“物种方程”（形态、分子和自然历史）。
