DOI: 10.5061/dryad.p2ngf1vt0
title: Origin, diversity, and biogeography of Antarctic scale worms (Polychaeta: Polynoidae): a wide-scale barcoding approach

description: Aim: 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, 3) species migrations
 across the Polar Front. In this study, we investigated which hypotheses
 best describe benthic invertebrate origins by examining Antarctic scale
 worms. Location: Southern Ocean, Kerguelen archipelago, South American
 peninsula, Indian Ocean, New Zealand. Taxon: Scale worm polychaetes
 (Polynoidae). Methods: We amassed 670 polynoids from the Southern Ocean
 and neighbouring areas and 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.
 Results: The Cox1 dataset provided the most illuminating insights into the
 evolution of polynoids. Eunoe sp. was present at South America and
 Kerguelen, in favour 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 cooccurrence 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. Main Conclusions: This study details the largest phylogenetic
 dataset assembled to date for Antarctic polynoids. These findings provide
 insight into past demographic events experienced by Antarctic marine
 benthos and identify multiple origin scenarios for contemporary
 polynoids. 
description: Polynoids were retrieved across several years aboard multiple
 research vessels, aided by an assortment of sampling equipment. Specimens
 processed within the context of this study were preserved either in 96°
 ethanol or at ‑80 °C. Each collected individual was identified to the
 lowest possible taxonomic level based on morphological characters. DNA was
 extracted from each specimen either by following a modified CTAB protocol
 (Doyle & Doyle 1987) or  shipped to the Canadian Center for DNA
 Barcoding (CCDB) at the University of Guelph to be processed following the
 CCDB automated standard protocols. PCR assays were performed using
 extracted DNA to amplify fragments of two mitochondrial genes, Cytochrome
 c oxidase subunit I (Cox1) and 16S ribosomal RNA (16S). Resulting PCR
 products were either submitted to Eurofins Scientific for purification and
 Sanger sequencing in both directions, using ABI BigDye® Terminator v3.1
 Cycle sequencing kit (Applied Biosystems) or underwent amplification and
 sequencing at CCDB. <br><br>Sources: Doyle, J, Doyle, J
 (1987). Genomic plant DNA preparation from fresh tissue-CTAB method.
 Phytochem Bulletin, 19(11), 11-15. <br>Canadian Center for DNA
 Barcoding (CCDB – University of Guelph, Canada):
 http://ccdb.ca/resources/
description: Resulting sequences were visualized and edited using
 Codoncode Aligner 7.1.2
 (CodonCode Corporation) and Geneious v.10.0.5 (Kearse et al.
 2012).