Origin, diversity, and biogeography of Antarctic scale worms (Polychaeta: Polynoidae): a wide-scale barcoding approach

• Published in: Ecology and Evolution
• Main Authors: Cowart, Dominique A, Schiaparelli, Stefano, Alvaro, Maria Chiara, Cecchetto, Matteo, Le Port, Anne-Sophie, Jollivet, Didier, Hourdez, Stephane
• Format: Article in Journal/Newspaper
• Language: English
• Published: WILEY 2022
• Subjects: Antarctic biogeography; DNA barcoding; Southern Ocean; benthic invertebrate; gene flow; polynoid; species connectivity; Antarc*; Antarctic; Tierra del Fuego
• Online Access: https://hdl.handle.net/11567/1103321; https://doi.org/10.1002/ece3.9093

The Antarctic marine environment hosts diversified and highly endemic benthos owing to its unique geologic and climatic history. Current warming trends have increased the urgency of understanding Antarctic species history to predict how environmental changes will impact ecosystem functioning. Antarctic benthic lineages have traditionally been examined under three hypotheses: (1) high endemism and local radiation, (2) emergence of deep-sea taxa through thermohaline circulation, and (3) species migrations across the Polar Front. In this study, we investigated which hypotheses best describe benthic invertebrate origins by examining Antarctic scale worms (Polynoidae). We amassed 691 polynoid sequences from the Southern Ocean and neighboring areas: the Kerguelen and Tierra del Fuego (South America) archipelagos, the Indian Ocean, and waters around New Zealand. We performed phylogenetic reconstructions to identify lineages across geographic regions, aided by mitochondrial markers cytochrome c oxidase subunit I (Cox1) and 16S ribosomal RNA (16S). Additionally, we produced haplotype networks at the species scale to examine genetic diversity, biogeographic separations, and past demography. The Cox1 dataset provided the most illuminating insights into the evolution of polynoids, with a total of 36 lineages identified. Eunoe sp. was present at Tierra del Fuego and Kerguelen, in favor of the latter acting as a migration crossroads. Harmothoe fuligineum, widespread around the Antarctic continent, was also present but isolated at Kerguelen, possibly resulting from historical freeze-thaw cycles. The genus Polyeunoa appears to have diversified prior to colonizing the continent, leading to the co-occurrence of at least three cryptic species around the Southern and Indian Oceans. Analyses identified that nearly all populations are presently expanding following a bottleneck event, possibly caused by habitat reduction from the last glacial episodes. Findings support multiple origins for contemporary Antarctic polynoids, and some ...