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

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.

Fig 1. Schematic representation of the integrative species delimitation method used to uncover Tiger Moth diversity along an elevational gradient in southern Brazilian Atlantic Forest.

Small black, white and grey squares in the upper right corner represent the possible rearrangements of the IMA species suggested by the analysis of the Barcode Index Numbers.

Fig 2. Correspondence between species delimited according to an Initial Morphological Assessment (IMA) and molecular operational taxonomic units delimited with the Barcode Index Number approach (BINs).

The inset figure shows the distribution of the rearrangements in the IMA species, as suggested by the BINs analysis.

Fig 3. Results of the Morphological Reassessment (MRA) to assess incongruences between species delimited according to the IMA and BIN systems.

Fig 4. Maximum intraspecific distance and distance to the nearest neighbor of the 157 species with two or more sequences delimited under the Initial Morphological Assessment (A) and Morphological Reassessment (B) approaches.

Fig 5. Recursive and Initial partitions delimited with the Automatic Barcode Gap Discovery approach (ABGD) used to uncover Tiger Moths diversity along an elevational gradient in southern Brazilian Atlantic Forest.