Distribution and species identification in the crustacean isopod genus Dynamene Leach, 1814 along the North East Atlantic-Black Sea axis

Abstract

Sphaeromatid isopods, such as Dynamene, are common and abundant members of the invertebrate fauna of littoral and shallow sublittoral substrates. Six species of Dynamene occur in the northern hemisphere. Only two species exist outside this range, in Australia. The distribution of the various species in the NE Atlantic-Black Sea axis has been controversial due to the difficulty in the identification of the different species. This has led to inaccurate records of their distribution, ultimately generating uncertain or faulty assessments on the biodiversity of these habitats. An update and a clarification about the distribution of this genus is therefore in order. In this study, we describe the distribution of Dynamene species in the light of new records from the NE Atlantic Ocean and its associated islands, and the Mediterranean, Black and Red Seas, and from re-examination of museum and several authors’ personal collections. Based on these observations, we extend the northern and southern limits of Dynamene bidentata (Adams); the western and southern limits of Dynamene magnitorata Holdich; the northern, eastern and western limits of Dynamene edwardsi (Lucas); and the eastern and western limits of Dynamene bifida Torelli. The range of Dynamene tubicauda Holdich is extended, but is still only known from the eastern Mediterranean. We also clarify the synonymy of Dynamene torelliae Holdich with Dynamene bicolor (Rathke), and the occurrence of Dynamene bicolor in the Black Sea. New distribution maps of the six Dynamene species are presented. Illustrated keys to the adult males and females of the northern hemisphere species are provided.

Deep segregation in the open ocean: Macaronesia as an evolutionary hotspot for low dispersal marine invertebrates

“…The diversity and distribution of the genus Dynamene in the Northern Hemisphere have been recently reviewed and updated (Vieira et al, ). The revised information was based on morphology, as well as on new and published occurrence records, including the Macaronesian archipelagos.…”

“…Because Dynamene species require specific habitats to reproduce (e.g. barnacles or crevices), intense reproductive competition among Dynamene individuals is suspected (Holdich, ; Vieira et al, ). The pattern observed in the D. edwardsi complex seems to fit the “founder takes all” density‐dependent process (Waters et al, ), where the first founders rapidly colonize a new habitat, but subsequent migrants are incapable of successfully colonizing the pre‐empted space.…”

“…Specimens were collected in the NE Atlantic (Vieira et al, ) between 2009 and 2015 among algae in the rocky shore intertidal (Figure ; Supporting Information Table ). Three species were sampled: D. bidentata , D. magnitorata and D. edwardsi .…”

“…The present study revealed twelve consistent MOTUs within the genus Dynamene in NE Atlantic, nine of which belong to the D. edwardsi complex and display an allopatric distribution. It is noteworthy that Dynamene is a genus with only six known species present in the Northern Hemisphere and just three in the NE Atlantic (Vieira et al, ). If the putative cryptic species here reported are confirmed by further studies (e.g.…”

“…Members of the genus Dynamene Leach, 1,814 are common and abundant on rocky intertidal and shallow subtidal habitats of the Northeast (NE) Atlantic Ocean, Mediterranean and Black Seas. Although eight Dynamene species were reported worldwide (six in the Northern Hemisphere), only three species are present in the NE Atlantic (Holdich, ; Vieira, Queiroga, Costa, & Holdich, ): D. bidentata (Adams, 1800), D. edwardsi (Lucas, 1849) and D. magnitorata Holdich, 1968. Consequently, in this study, we aim to exploit an ideal opportunity to investigate the role of Macaronesian islands in shaping the phylogeography and evolutionary history of marine invertebrates lacking a pelagic dispersal stage.…”