The challenge of integrative taxonomy of rare, deep-water gastropods: the genus Exilia (Neogastropoda: Turbinelloidea: Ptychatractidae)

According to a recent taxonomic revision by Kantor et al. (2001), the neogastropod genus Exilia Conrad, 1860, comprises ten mostly rare species that live at depths between 200 and 2000 m. Adult Exilia measure between 30 and 90 mm in shell length, and the genus is mostly represented in museum collections by empty shells. The abundance of this genus is low in the wild, but recent expeditions organized by the Museum national d'Histoire naturelle have yielded several dozen specimens. These new collections include samples preserved for molecular studies. Here, we present the results of the first molecular systematic study of Exilia. Our aim was to investigate the species limits proposed by Kantor et al. (2001) on the basis of shell and anatomical characters. Analysis of DNA sequence data for the cytochrome c oxidase I gene suggests that Exilia hilgendorfi, previously considered to be a single, polymorphic and broadly distributed species, is a complex of at least six species (four of which we sequenced). Two of these species, Exilia cognata n. sp. and E. fedosovi n. sp., are described as new to science. Exilia gracilior, E. claydoni and E. prellei are resurrected from the synonymy of Exilia hilgendorfi; of these three, only the last was sequenced. Exilia vagrans is a welldefined taxon, but our molecular systematic data shows that it consists of two distinct species, which occur sympatrically off Taiwan and are strikingly similar in shell and radular morphology; due to the absence of DNA sequence data from the type locality of E. vagrans (Vanuatu), it is unclear to which of these two species the name would apply. Exilia karukera n. sp., which is conchologically very similar to E. vagrans, was discovered off Guadeloupe, represents the first record of the genus from the Atlantic. For E. elegans, which was previously known only from a single shell, we provide new data including new distributional records (South Africa and the Mozambique Channel), details of the radula and DNA sequence data.