DNA barcoding as a tool to facilitate the taxonomy of hermit crabs (Decapoda: Anomura: Paguroidea)

Abstract

DNA barcoding has become an important aspect in biodiversity research, but is ineffective without comprehensive databases that can relate molecular sequences to scientific names. Hermit crabs, or paguroids, are an important component of the marine benthos, and are vastly understudied in southern Africa, a globally important bioregion. The study provides 194 cytochrome c oxidase subunit I (COI) barcode sequences (> 550 bp) of 43 nominal and 12 putative species from 19 genera and four families of Paguroidea. Preliminary COI-based phylogenetic analysis suggested some overall pattern of monophyly in the Parapaguridae and PaguristesDana, 1851 and DardanusPaulˊson, 1875. Large groups in Diogenidae, however, such as CalcinusDana, 1851 and DiogenesDana, 1851, were recovered as poly- or paraphyletic. Testing the dataset for barcoding efficacy revealed that the technique can reach identification rates near 100% success. A barcoding gap was apparent for almost all but one problematic taxon. The optimum threshold range to discriminate between species for this set of data was calculated at 3.7–3.9%, although the overall mean intraspecific distance was well below 1%. Furthermore, glaucothoe larvae of two deep-water paguroids were matched to names in the new molecular library. The COI marker alone, however, did not provide clear species identifications in three problematic species, Areopaguristes cf. jousseaumei (Bouvier, 1892), Goreopagurus pooreiLemaitre & McLaughlin, 2003, and Pagurus cuanensisBell, 1846. Despite the dataset having considerable species coverage of 55 total taxa, it is still estimated to be only about 50% complete in terms of the South African fauna. Future work should therefore increase coverage to other species in South Africa and expand geographic coverage for widely distributed species.