Oceanic boundaries in the western Atlantic delimitate novel lineages in the tanaidacean Chondrochelia dubia (Tanaidacea: Leptocheliidae) species complex

Chondrochelia dubia is regarded as a cosmopolitan tanaidacean with tubicolous lifestyle that is commonly found in shallow waters. The lack of a dispersive larval stage, however, suggests that several endemic cryptic species might exist. Here, we studied C. dubia specimens collected from across 5000 km of distribution in the western Atlantic. We confirm its species complex status and identify five independent species, including C. brasiliensis comb. nov. Using molecular analyses, we show that the genetic diversity and structure of C. dubia and C. brasiliensis strongly differ from one another, suggesting independent evolution of each lineage with a geographic separation at the Paraguaçu River mouth. The paleodistribution simulation suggests a considerable spatio-temporal expansion for C. dubia and C. brasiliensis since the Last Glacial Maximum (LGM), when the species was restricted to the submerged continental shelf. In summary, we observe that the simplified morphology of the Chondrochelia dubia complex hides a great diversity of species within the western Atlantic, approximately one per ecoregion. Combination of detailed morphological analyses with molecular and ecological data shall further elucidate the systematics of the Chondrochelia dubia complex worldwide.