The phylogenetics and population structure of a species complex of deep-sea scale worms

Presented by Niamh Ryan

Honours Student , The University of Sydney

Supervisors: Prof Simon Ho (USyd) and Dr Elena Kupriyanova (AM)

The distribution of marine annelids in the deep sea remains poorly understood, with taxa's broad ranges potentially reflecting the presence of species complexes. DNA barcoding can efficiently identify genetically distinct lineages, however, mitonuclear discordance may limit the accuracy of these inferences. The addition of genome-wide SNP data for species delimitation provides a high resolution of information and can account for this discordance. This project focuses on annelids of the genus Laetmonice, family Aphroditidae. Recent study of the genus in Australia described four new species with bathymetrically isolated distributions. Niamh analysed specimens collected from Australian territorial waters (190 - 5,000 m) alongside previously described specimens. Using both mitochondrial barcoding (COI and 16S) and genomic data (SNPs) Niamh identified putative species and assessed current species hypotheses.

Despite limitations in the results produced by both datasets, inference drawn from their comparison allowed for a robust exploration of species boundaries, suggesting seven distinct genetic lineages withing the genus, five of which agree with currently valid species, and two which may represent undescribed species. These results demonstrate the value of utilising multiple methods in proposing species hypotheses and forms the basis of morphological examination of two putative undescribed species in the genus Laetmonice.