Range-wide phylogeography and taxonomy of the marine rock pools dweller Tigriopus fulvus (Fischer, 1860) (Copepoda, Harpacticoida)

In the light of the wide distribution and ecological importance of the genus Tigriopus in coastal rock pool habitats, and of its frequent use in aquaculture and as a model organism, we investigated the identity of the Atlantic–Mediterranean Tigriopus populations and elucidated their taxonomy and patterns of morphological and genetic diversity. In order to reach these goals, an “integrative taxonomy” multisource approach was implemented. First, we investigated the constancy and taxonomical value of the morphological characters currently used to distinguish among the Tigriopus species occurring in the Mediterranean and in Eastern Atlantic area north of the Tropic of Cancer, and checked the actual morphological differences possibly present among topotypical samples of Tigriopus fulvus fulvus (Fischer, 1860) and its two subspecies Tigriopus fulvus adriaticus Van Douwe, 1913 and Tigriopus fulvus algiricus Monard, 1935. Then, we sequenced fragments of mitochondrial (12S) and nuclear (28S) genes. In the frame of this study, different “DNA taxonomy” approaches were implemented in order to check whether the subspecies of Tigriopus fulvus were actually lineages evolving independently, that is, valid species according to the “evolutionary genetic species concept.” The results coherently indicate the presence of a single species, characterized by constant morphology and a noteworthy geographically based genetic structure in the whole study area. No morphological or genetic support was found for the taxa of allegedly subspecific rank within T. fulvus, which are thus to be considered junior synonyms of T. fulvus s.s. Finally, a restricted locus typicus is established for T. fulvus, and a neotype is designated.