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

Abstract

The philosophical basis and utility of DNA barcoding have 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 vs. 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.

Phylogeography of a good Caribbean disperser: Argiope argentata (Araneae, Araneidae) and a new ‘cryptic’ species from Cuba

“…material 4). We sequenced a fragment of the mitochondrial ‘DNA barcode’ Cytochrome c oxidase subunit 1-COI, a useful marker at low taxonomic levels in spiders, to establish boundaries among species (Čandek and Kuntner 2015; Hebert et al 2003). To amplify COI we used the primers LCO 1490 and HCO 2198 (Folmer et al 1994).…”

DNA barcodes for bio-surveillance: regulated and economically important arthropod plant pests

“…Work on this group has demonstrated the efficacy of DNA barcoding in identifying known species (Wilson et al 2013;Dinca et al 2015) and in revealing cryptic species complexes (Burns et al 2008;Huemer et al 2014a). It has also shown that there is very limited geographic variation in barcode sequences in populations of most species, so increased geographic scale does not reduce the success of species identification (Lukhtanov et al 2009;Huemer et al 2014b, Candek andKuntner 2015). However, in certain groups, such as diving beetles of the tribe Agabini (Bergsten et al 2012), the correlation between genetic and geographic distances is strong enough to impact the success of species identification unless sampling of each species is fairly comprehensive.…”

Systematics of the Madagascar Anelosimus spiders: remarkable local richness and endemism, and dual colonization from the Americas

“…Paucity of specimens of some species prevented establishing a ‘barcoding gap’ (e.g. Čandek and Kuntner 2015) but for the most closely related species that have multiple specimens available all are separated by a gap of >10 times greater inter- than intraspecific genetic distances (Table 1). All types are deposited in the National Museum of Natural History, Smithsonian Institution (NMNH).…”