DNA barcoding reveals new insights into the diversity of Antarctic species of Orchomene sensu lato (Crustacea: Amphipoda: Lysianassoidea) C. Havermans a,b,n , Z.T. Nagy a , G. Sonet a , C. De Broyer a , P. Martin a a Royal Belgian Institute of Natural Sciences, Rue Vautier 29, B-1000 Brussels, Belgium b Laboratory of Marine Biology, Place Croix du Sud 3, Catholic University of Louvain, B-1348 Louvain-la-Neuve, Belgium article info Available online 28 October 2010 Keywords: DNA barcoding Genetic diversity Species Amphipoda Lysianassoidea Southern Ocean abstract Recent molecular analyses revealed that several so-called ‘‘circum-Antarctic’’ benthic crustacean species appeared to be complexes of cryptic species with restricted distributions. In this study we used a DNA barcoding approach based on mitochondrial cytochrome oxidase I gene sequences in order to detect possible cryptic diversity and to test the circumpolarity of some lysianassoid species. The orchomenid genus complex consists of the genera Abyssorchomene, Falklandia, Orchomenella, Orchomenyx and Pseudorchomene. Species of this genus complex are found throughout the Southern Ocean and show a high species richness and level of endemism. In the majority of the studied species, a genetic homogeneity was found even among specimens from remote sampling sites, which indicates a possible circum-Antarctic and eurybathic distribution. In four investigated species (Orchomenella (Orchomenopsis) acanthurus, Orchomenella (Orchomenopsis) cavimanus, Orchomenella (Orchomenella) franklini and Orchomenella (Orchomenella) pinguides), genetically divergent lineages and possible cryptic taxa were revealed. After a detailed morphological analysis, O. (O.) pinguides appeared to be composed of two distinct species, formerly synonymized under O. (O.) pinguides. The different genetic patterns observed in these orchomenid species might be explained by the evolutionary histories undergone by these species and by their different dispersal and gene flow capacities. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction According to most estimations on global biodiversity, the majority of species living on this planet are currently undescribed (Novotny et al., 2002; Blaxter, 2003, 2004; Bouchet, 2006). Aiming to have a ‘‘complete’’ account of all living organisms would require more work than the present manpower and technology can handle. Moreover, in the context of the current biodiversity crisis and the declining number of taxonomists, several authors suggest the use of DNA barcoding to accelerate and simplify species identification (Hebert et al., 2003a,b; Blaxter, 2004; Janzen et al., 2005; Schander and Willassen, 2005; Schindel and Miller, 2005). DNA barcoding uses a short DNA sequence as the standard genetic marker for species identification (a ca. 648 bp segment near the 5 0 end of the mitochondrial cytochrome oxidase I gene, COI, for animals). The barcode sequence from each unknown specimen is compared with a reference library of sequences derived from specimens of known identity (Hajibabaei et al., 2007). This sequence library is currently being established. This approach speeds up species identification and also facilitates the discovery of undescribed species (Witt et al., 2003). The efficiency of a barcoding marker in species delimitation depends on the separation between intra- and interspecific divergences (Hebert et al., 2003a,b; Meyer and Paulay, 2005; Waugh, 2007). In accordance with the biological species definition, intraspecific genetic distances have to be generally smaller (mostly by an order of magnitude) than interspecific genetic distances. This provides the basis for species delimitation (Waugh, 2007; Meier et al., 2008). In several animal taxa, the effectiveness of this approach has been confirmed, such as in birds (Hebert et al., 2004b), fish (Ward et al., 2005), molluscs (Meyer and Paulay, 2005), spiders (Barrett and Hebert, 2005) and several groups of butterflies (Hebert et al., 2004a; Janzen et al., 2005; Hajibabaei et al., 2006). In poorly studied groups, DNA barcoding can be performed prior to ‘‘conventional’’, morphology-based taxonomic studies in order to quickly sort specimens into genetically divergent groups (Hajibabaei et al., 2007). However, the DNA barcoding approach is not without controversy when it is considered as a tool for classification and identification (e.g., Lipscomb et al., 2003; Moritz and Cicero, 2004; Will and Rubinoff, 2004). It has raised some debates about traditional Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/dsr2 Deep-Sea Research II 0967-0645/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.dsr2.2010.09.028 n Corresponding author at: Department of Freshwater Biology, Royal Belgian Institute of Natural Sciences, Rue Vautier 29, B-1000 Brussels, Belgium. Tel.: +32 2 627 42 78; fax: +32 2 627 42 77. E-mail addresses: chavermans@naturalsciences.be (C. Havermans), zoltan-tamas.nagy@naturalsciences.be (Z.T. Nagy), gontran.sonet@naturalsciences.be (G. Sonet), claude.debroyer@naturalsciences.be (C. De Broyer), patrick.martin@naturalsciences.be (P. Martin). Deep-Sea Research II 58 (2011) 230–241