Data from: DNA barcoding gap: reliable species identification over morphological and geographical scales

The philosophical basis, and utility of DNA barcoding has been a subject of numerous debates. While most literature embraces it, some studies continue to question its use in dipterans, butterflies, and marine gastropods. Here, we explore the utility of DNA barcoding in identifying spider species that vary in taxonomic affiliation, morphological diagnosibility and geographic distribution. Our first test searched for a “barcoding gap” by comparing intra- and interspecific means, medians and overlap in more than 75,000 computed Kimura 2 parameter (K2P) genetic distances in three families. Our second test compared K2P distances of congeneric species with high versus low morphological distinctness in 20 genera of 11 families. Our third test explored the effect of enlarging geographical sampling area at a continental scale on genetic variability in DNA barcodes within 20 species of nine families. Our results generally point towards a high utility of DNA barcodes in identifying spider species. However, the size of the barcoding gap strongly depends on taxonomic groups and practices. It is becoming critical to define the barcoding gap statistically more consistently, and to document its variation over taxonomic scales. Our results support models of independent patterns of morphological and molecular evolution by showing that DNA barcodes are effective in species identification regardless of their morphological diagnosibility. We also show that DNA barcodes represent an effective tool for identifying spider species over geographic scales, yet their variation contains useful biogeographic information.DNA条形码（DNA barcoding）的哲学基础与应用价值一直是诸多学术争论的焦点议题。尽管绝大多数相关研究认可其应用价值，但仍有部分研究对其在双翅目昆虫、蝶类及海洋腹足类中的适用性提出质疑。本研究旨在探讨DNA条形码在鉴定不同分类归属、形态鉴别能力及地理分布模式的蜘蛛物种中的应用潜力。第一项实验通过比对3个科的超过75000对计算得到的木村二参数（Kimura 2 parameter, K2P）遗传距离的种内、种间均值、中位数及重叠度，以探寻‘条形码间隙’；第二项实验针对11个科的20个属，比对了形态差异度高低不同的同属物种间的K2P遗传距离；第三项实验则探究了在大陆尺度下扩大地理采样范围对9个科20个物种种内DNA条形码遗传变异的影响。本研究结果总体表明，DNA条形码在蜘蛛物种鉴定中具备较高的应用价值，但条形码间隙的大小强烈依赖于具体的类群与实验操作规范。以更统一的统计学方法定义条形码间隙，并记录其在不同分类层级上的变异，已成为亟待解决的关键问题。本研究结果证实，无论物种的形态鉴别能力如何，DNA条形码均可有效用于物种鉴定，这支持了形态进化与分子进化模式相互独立的理论模型。同时，本研究还证明，DNA条形码可作为跨地理尺度鉴定蜘蛛物种的有效工具，其序列变异还蕴含了极具价值的生物地理学信息。