Fast Census of Moth Diversity in the Neotropics: A Comparison of Field-Assigned Morphospecies and DNA Barcoding in Tiger Moths

The morphological species delimitations (i.e. morphospecies) have long been the best way to avoid the taxonomic impediment and compare insect taxa biodiversity in highly diverse tropical and subtropical regions. The development of DNA barcoding, however, has shown great potential to replace (or at least complement) the morphospecies approach, with the advantage of relying on automated methods implemented in computer programs or even online rather than in often subjective morphological features. We sampled moths extensively for two years using light traps in a patch of the highly endangered Atlantic Forest of Brazil to produce a nearly complete census of arctiines (Noctuoidea: Erebidae), whose species richness was compared using different morphological and molecular approaches (DNA barcoding). A total of 1,075 barcode sequences of 286 morphospecies were analyzed. Based on the clustering method Barcode Index Number (BIN) we found a taxonomic bias of approximately 30% in our initial morphological assessment. However, a morphological reassessment revealed that the correspondence between morphospecies and molecular operational taxonomic units (MOTUs) can be up to 94% if differences in genitalia morphology are evaluated in individuals of different MOTUs originated from the same morphospecies (putative cases of cryptic species), and by recording if individuals of different genders in different morphospecies merge together in the same MOTU (putative cases of sexual dimorphism). The results of two other clustering methods (i.e. Automatic Barcode Gap Discovery and 2% threshold) were very similar to those of the BIN approach. Using empirical data we have shown that DNA barcoding performed substantially better than the morphospecies approach, based on superficial morphology, to delimit species of a highly diverse moth taxon, and thus should be used in species inventories.

形态学物种界定（morphospecies，形态种）长期以来都是规避分类学障碍、在高度多样的热带与亚热带区域开展昆虫类群生物多样性比较研究的最优手段。然而，DNA条形码技术的发展展现出替代（或至少补充）形态种方法的巨大潜力，其优势在于依托计算机程序甚至在线平台实现的自动化分析流程，而非通常具备主观性的形态特征。本研究在一片高度濒危的巴西大西洋森林中，利用灯光诱捕器开展了为期两年的大规模蛾类采样，以近乎全面完成灯蛾亚科（Arctiinae，夜蛾总科: 裳蛾科）的物种普查，并通过不同形态学与分子方法（DNA条形码技术）比较其物种丰富度。本研究共分析了286个形态种的1075条条形码序列。基于条形码索引号（Barcode Index Number，BIN）的聚类方法，我们发现初始形态学鉴定存在约30%的分类学偏差。不过，重新开展形态学评估后发现：若对源自同一形态种、隶属于不同分子操作分类单元（molecular operational taxonomic units，MOTUs）的个体（即疑似隐存种案例）的生殖器形态差异进行评估，并记录不同形态种间的雌雄个体是否会聚类至同一MOTU（即疑似雌雄二型性案例），则形态种与分子操作分类单元的匹配率最高可达94%。另外两种聚类方法——自动条形码间隙发现法（Automatic Barcode Gap Discovery，ABGD）与2%阈值法的结果与BIN方法高度一致。基于本研究的实证数据，相较于仅依赖表面形态学的形态种方法，DNA条形码技术在界定高度多样的蛾类类群物种时表现更优，因此应将其应用于物种编目工作中。