Abstract
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.
Highlights
The immense work of cataloguing diversity of all arthropods on Earth remains one of the most challenging scientific ambitions of our day
DNA barcoding—a 658-bp fragment of the mitochondrial gene cytochrome c oxidase I (COI)–which has been widely used for more than a decade, shows a high correspondence with taxonomical identification, for distinguishing arthropod species, e.g. [12,13,14,15,16,17]. This method has two advantages compared to the morphospecies approach: (1) two or more people can unambiguously assign individuals to species without requiring any taxonomic expertise; and (2) a species identification can be obtained if a barcode sequence is compared to sequences of conspecifics deposited in a database for which the taxonomic name is already known (i.e. DNA barcode library, [18])
We highlight the performance of DNA taxonomy in assessing biodiversity of moths compared to the superficial morphological approach, we suggest that additional data, such as life-history traits and nuclear genes, should be incorporated for a more accurate delineation of species boundaries, especially in putative cases of cryptic diversity
Summary
The immense work of cataloguing diversity of all arthropods on Earth remains one of the most challenging scientific ambitions of our day. The ability to reliably assign unknown individuals to species is critical in assessing arthropod biodiversity [4,5] and often represents a considerable challenge in tropical regions, requiring scarcely available expertise and important resources. The sorter must recognize units without the use of taxonomic sources, relying exclusively on superficial morphological characteristics [11]. This appears to be a tempting approach different operators rarely reproduce the same results and the correspondence between morphospecies and taxonomic species can vary extensively, with error rates being higher than 100%, depending on which groups are considered [5]. This method has two advantages compared to the morphospecies approach: (1) two or more people can unambiguously assign individuals to species without requiring any taxonomic expertise; and (2) a species identification can be obtained if a barcode sequence is compared to sequences of conspecifics deposited in a database for which the taxonomic name is already known (i.e. DNA barcode library, [18])
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