Biogeography of the Antarctic dragonfishes Acanthodraco dewitti and Psilodraco breviceps with re-description of Acanthodraco dewitti larvae (Notothenioidei: Bathydraconidae)

Abstract

Antarctic dragonfishes (Bathydraconidae) of the suborder Notothenioidei are found only in the Southern Ocean where they diversified in habitats from the surface to the bathypelagic zone thousands of meters deep. Among dragonfishes, the pelagic Gymnodraconinae sister species Acanthodraco dewitti and Psilodraco breviceps remain poorly known. Although A. dewitti is thought to be restricted to Antarctic waters and P. breviceps to be endemic to South Georgia Island, several P. breviceps specimens have occasionally been reported in coastal Antarctica. Here we investigated the molecular genetic identity of the two species and their geographic distribution. Three mitochondrial genetic markers (mt-cyb, mt-co1, and mt-nd2) identified two dragonfish larvae collected on the West Antarctic Peninsula as A. dewitti and showed that all six specimens with available genetic data and reported to be P. breviceps collected in Antarctic waters were also A. dewitti. These results support the allopatric distribution of the two species, with P. breviceps being endemic to South Georgia Island and A. dewitti being endemic to Antarctic waters, potentially with a circumpolar distribution. The biogeography of the sister species A. dewitti and P. breviceps is likely similar to the allopatric distribution of the congeneric sister dragonfish species Parachaenichthys charcoti and P. georgianus. These considerations suggest that the Antarctic Circumpolar Current may geographically isolate the sub-Antarctic and Antarctic species of both sister species pairs, limiting gene flow and promoting speciation. Furthermore, we provide a detailed description of the A. dewitti larvae to supply characteristic morphological features differentiating A. dewitti and P. breviceps larvae.