Morphological diversity and a ribosomal phylogeny of Rhabdopleura (Hemichordata: Graptolithina) from the Western Pacific (Singapore and New Zealand), with implications for a re-evaluation of rhabdopleurid species diversity

The recent discovery of Rhabdopleura in Singapore and the chance collecting of fresh material from northern New Zealand (Three Kings Shelf) provided an opportunity to sequence the specimens with an aim to determine their species identity. Phylogeny reconstructions of two new Rhabdopleura taxa based on ribosomal and mitochondrial genes suggest a different identity from known samples, including putative Rhabdopleura annulata , first described from the Three Kings Shelf but sequenced from the Great Barrier Reef. Pairwise distances between rhabdopleurids for the 16S rRNA locus were several magnitudes larger than that of 18S rRNA, and might potentially be a suitable barcoding gene once sufficient samples of conspecifics are collected to determine the barcoding gaps. Type material of R. annulata was re-examined, as well as Rhabdopleura material from eight other New Zealand localities from north of subtropical Raoul Island (Kermadec Ridge) at ~29° S to the subantarctic Campbell Plateau at ~49° S. Six morphological characters, four of them new, were applied to all samples. The findings from morphology suggest (1) the holotype and cotype of R. annulata might not be conspecific; (2) there are 3–4 variants (species?) on the Three Kings Shelf; and (3) there are 2–3 additional variants (species?) elsewhere in the New Zealand region.