Prospects for using DNA barcoding to identify spiders in species-rich genera

Abstract

While previous research has indicated the utility of DNA barcoding in identifying spider species sampled from a localized region, the eff ectiveness of this method over a broader geographic scale and with denser taxon sampling has not yet been extensively considered. Using both new and published data from 1801 individuals belonging to 361 morphospecies, this study examined intra- and interspecifi c divergences for 19 genera that were each represented by at least 10 morphospecies. We particularly focused on increasing species-level sampling in order to better characterize levels of interspecifi c divergence within species-rich genera and to examine the prevalence of a “barcode gap” (discontinuity between intra- and interspecifi c di- vergences). Overall, the mean intraspecifi c divergence value was found to be 2.15%, the average maximum intraspecifi c divergence was 3.16%, while the mean divergence between nearest interspecifi c neighbours was 6.77%, demonstrating the typical presence of a barcode gap. Of the 66% of morphospecies that formed monophyletic sequence clusters, the majority (92.5%) possessed a barcode gap. We also examine possible biological explanations for the large proportion of paraphyletic and polyphyletic clusters and discuss the need for further taxonomic investigations. Th e overlap between intra- and interspecifi c divergences was not unexpected for some ‘species’, such as Pardosa groenlandica, since prior morphological studies have suggested that it is an example of a species complex. However, other cases of high intraspecifi c divergences may refl ect cryptic species diversity, indicating the need for a taxonomic approach that combines both morphological and molecular methods.