Data from: The importance of taxonomic resolution for additive beta diversity as revealed through DNA barcoding

Additive diversity partitioning (α, β, and γ) is commonly used to study the distribution of species-level diversity across spatial scales. Here, we first investigate whether published studies of additive diversity partitioning show signs of difficulty attaining species-level resolution due to inherent limitations with morphological identifications. Second, we present a DNA barcoding approach in order to delineate specimens of stream caddisfly larvae (order Trichoptera) and considered the importance of taxonomic resolution on classical (additive) measures of beta (β) diversity. Caddisfly larvae were sampled using a hierarchical spatial design in two regions (sub-Arctic Churchill, Manitoba, Canada; temperate Pennsylvania, USA) and then additively partitioned according to Barcode Index Numbers (molecular clusters that serve as a proxy for species), genus, and family levels; diversity components were expressed as proportional species turnover. We screened 114 articles of additive diversity partitioning and found that a third reported difficulties with achieving species-level identifications, with a clear taxonomic tendency towards challenges identifying invertebrate taxa. Regarding our own study, caddisfly BINs appeared to show greater sub-regional turnover (e.g. proportional additive β) compared to genus or family levels. Diversity component studies failing to achieve species resolution due to morphological identifications may therefore be underestimating diversity turnover at larger spatial scales.

加性多样性分区（Additive diversity partitioning，涵盖α、β和γ三个维度）常被用于探究物种多样性在空间尺度上的分布格局。本研究首先考察已发表的加性多样性分区相关研究是否存在因形态鉴定固有局限而难以达成物种级分辨度的问题；其次，本研究提出一种DNA条形码（DNA barcoding）方法，用以界定溪流石蛾幼虫（毛翅目（Trichoptera））的标本，并探讨分类学分辨度对经典（加性）β多样性测度的影响。研究采用分层空间设计，在两个区域——加拿大曼尼托巴省的亚北极丘吉尔港、美国宾夕法尼亚州的温带区域——采集石蛾幼虫样本，随后分别以条形码索引编号（Barcode Index Numbers，即作为物种替代物的分子聚类簇）、属级与科级水平开展加性多样性分区，多样性组分以物种周转比例的形式呈现。我们检索了114篇加性多样性分区相关研究论文，发现其中三分之一的研究报告了难以实现物种级鉴定的问题，且这类鉴定难题明显集中于无脊椎动物类群。就本研究而言，相较于属级或科级水平，石蛾的条形码索引编号（BINs）展现出更强的亚区域物种周转特征（例如比例加性β多样性）。因此，那些因形态鉴定局限而无法达到物种级分辨度的多样性组分研究，可能低估了更大空间尺度下的多样性周转情况。