Deep Downunder: Integrative taxonomy of Austrobela, Spergo, Theta and Austrotheta (Gastropoda: Conoidea: Raphitomidae) from the deep sea of Australia

Abstract

Recent sampling efforts in the deep seas of southern and eastern Australia have generated a wealth of DNA-suitable material of neogastropods of the family Raphitomidae. Based on this material, a molecular phylogeny of the family has revealed a considerable amount of genus and species level lineages previously unknown to science. These taxa are now the focus of current integrative taxonomic research. As part of this ongoing investigation, this study focuses on the genera Austrobela, Austrotheta (both Criscione, Hallan, Puillandre & Fedosov, 2020), Spergo Dall, 1895 and Theta Clarke, 1959. We subjected a comprehensive mitochondrial DNA dataset of representative deep-sea raphitomids to Automatic Barcode Gap Discovery, which recognized 24 primary species hypotheses (PSHs). Following additional evaluation of shell and radular features, as well as examination of geographic and bathymetric ranges, 18 of these PSHs were converted to secondary species hypotheses (SSHs). Based on the evidence available, the most likely speciation mechanisms involved were evaluated for each pair of sister SSHs, including niche partitioning. Eleven SSHs were recognized as new and their systematic descriptions are provided herein. Of these, four were attributed to Austrobela, one to Austrotheta, four to Spergo and two to Theta. While all new species are endemic to Australian waters, other species studied herein exhibit wide Indo-Pacific distributions, adding to the growing body of evidence suggesting that wide geographic ranges in deep-sea Raphitomidae are more common than previously assumed.