Morphological boundaries between species of the maculatipes-group in the ghost spider genus Sanogasta Mello-Leitão are ambiguous, and the most widespread species, S. maculatipes, is unusually variable and may represent multiple cryptic species. To resolve these issues, we perform a geometric morphometric analysis on the female genitalia of the group, visualizing and testing for differences in shape between described species, and between putative cryptic species within S. maculatipes. We complement this with a multi-locus phylogenetic analysis of the group, to place the morphological results in a phylogenetic context. Our study reveals that two species in the group, S. alticola and S. mandibularis, are morphologically and molecularly distinct lineages that can be objectively distinguished. However, we reveal that S. maculatipes actually consists of two widespread sister species which occur in sympatry throughout the grasslands of northern Argentina. We further discover a geographical cline in the shape of the female genitalia of one of these sister species, such that specimens from the east and west of the range display morphological differences comparable to those between species, despite being virtually identical at the COI locus. Our study demonstrates the strength of a geometric morphometric approach for delimiting species in species-complexes where morphological differences are subtle and confounding factors such as overlapping ranges, allometry and high levels of intraspecific variation are present.

中文翻译：

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几何形态测量学揭示了幽灵蜘蛛属中的姐妹物种和生殖器形态的cline

鬼蜘蛛属Sanogasta Mello-Leitão 中maculatipes组的物种之间的形态边界不明确，而分布最广的物种S. maculatipes异常多变，可能代表多个神秘物种。为了解决这些问题，我们对该组的女性生殖器进行了几何形态测量分析，可视化和测试所描述物种之间以及S. maculatipes内推定的隐性物种之间的形状差异。我们通过对该组的多位点系统发育分析对此进行补充，以将形态学结果置于系统发育背景中。我们的研究表明，该组中的两个物种S. alticola和S. mandibularis是可以客观区分的形态和分子不同的谱系。然而，我们发现S. maculatipes实际上由两个广泛分布的姊妹物种组成，它们在阿根廷北部的草原上出现。我们进一步发现了这些姐妹物种之一的雌性生殖器形状的地理倾斜，因此来自该范围东部和西部的标本显示出与物种之间相当的形态差异，尽管在 COI 轨迹上几乎相同。我们的研究证明了几何形态测量方法在物种复合体中划定物种的优势，其中形态差异是微妙的，并且存在诸如重叠范围、异速生长和高水平的种内变异等混杂因素。