Department of Entomology and Nematology, University of California, Davis, CA, USA.
Department of Biology, Millsaps College, Jackson, MS, USA.
Mol Ecol. 2020 Jun;29(12):2269-2287. doi: 10.1111/mec.15483. Epub 2020 Jun 17.
Although species delimitation can be highly contentious, the development of reliable methods to accurately ascertain species boundaries is an imperative step in cataloguing and describing Earth's quickly disappearing biodiversity. Spider species delimitation remains largely based on morphological characters; however, many mygalomorph spider populations are morphologically indistinguishable from each other yet have considerable molecular divergence. The focus of our study, the Antrodiaetus unicolor species complex containing two sympatric species, exhibits this pattern of relative morphological stasis with considerable genetic divergence across its distribution. A past study using two molecular markers, COI and 28S, revealed that A. unicolor is paraphyletic with respect to A. microunicolor. To better investigate species boundaries in the complex, we implement the cohesion species concept and use multiple lines of evidence for testing genetic exchangeability and ecological interchangeability. Our integrative approach includes extensively sampling homologous loci across the genome using a RADseq approach (3RAD), assessing population structure across their geographic range using multiple genetic clustering analyses that include structure, principal components analysis and a recently developed unsupervised machine learning approach (Variational Autoencoder). We evaluate ecological similarity by using large-scale ecological data for niche-based distribution modelling. Based on our analyses, we conclude that this complex has at least one additional species as well as confirm species delimitations based on previous less comprehensive approaches. Our study demonstrates the efficacy of genomic-scale data for recognizing cryptic species, suggesting that species delimitation with one data type, whether one mitochondrial gene or morphology, may underestimate true species diversity in morphologically homogenous taxa with low vagility.
尽管物种界定可能存在很大争议，但开发可靠的方法来准确确定物种界限是编目和描述地球迅速消失的生物多样性的必要步骤。蜘蛛物种的界定仍然主要基于形态特征；然而，许多狼蛛种群在形态上彼此无法区分，但在分子上却有相当大的差异。我们研究的重点是包含两个共生种的 Antrodiaetus unicolor 种复合体，表现出这种相对形态稳定的模式，在其分布范围内存在相当大的遗传分歧。过去的一项研究使用了两个分子标记，COI 和 28S，发现 A. unicolor 在相对于 A. microunicolor 是并系的。为了更好地研究该复合体中的物种界限，我们采用了凝聚物种概念，并使用多种证据来检验遗传可交换性和生态可互换性。我们的综合方法包括使用 RADseq 方法（3RAD）广泛采样基因组同源基因座，使用多种遗传聚类分析评估其地理分布范围内的种群结构，包括结构、主成分分析和最近开发的无监督机器学习方法（变分自动编码器）。我们通过使用基于生态位的分布模型的大规模生态数据来评估生态相似性。根据我们的分析，我们得出结论，这个复合体至少还有一个其他物种，并确认了以前采用不那么全面的方法确定的物种界限。我们的研究表明，基因组规模的数据对于识别隐种是有效的，这表明，无论使用一种线粒体基因还是形态学，仅使用一种数据类型进行物种界定，可能会低估在形态同质、迁移能力低的类群中真正的物种多样性。
