Tri-oceanic connectivity of the supposedly cosmopolitan polychaete, Harmothoe imbricata (Annelida: Polynoidae): insights from the COI marker

ABSTRACT

In this study, we investigated the global population genetic structure of the polychaete, Harmothoe imbricata, to determine connectivity patterns within the species. We sequenced the mtDNA marker, cytochrome c oxidase I (COI) from 29 specimens sampled across three sites from the New England coast of the United States. These were supplemented with 145 archived sequences from GenBank and the Barcode of Life Database, representing 16 global populations, which encompassed three broadly defined marine biogeographic regions: the Atlantic, Pacific and Arctic. The resulting haplotype network and pairwise AMOVA results showed marked structure across all the major biogeographic regions and also provides evidence for cryptic diversity in the species. Haplotypes from Arctic populations were more closely related to each other than those from the northwestern and northeastern Atlantic. Two evolutionary divergent lineages were recovered from Los Angeles, California and Manitoba, Canada. The highest genetic diversity was observed in the Arctic populations, providing evidence for an Arctic origin for H. imbricata. While human-mediated introductions may have likely contributed to some of the genetic patterns observed in this study, future work should incorporate a nuclear DNA component which could shed more light on contemporary movement of this species across large spatial scales.

KEYWORDS:

• cryptic
• species
• connectivity
• introduction
• Arctic
• Pleistocene

Acknowledgements

The authors would like to acknowledge the gracious support of the following sponsors which allowed for the collection of New England specimens: the Buzzards Bay National Estuary Program, the Casco Bay Estuary Partnership, the Massachusetts Bays National Estuary Program and the Massachusetts Office of Coastal Zone Management. Lab space for initial identification was graciously provided by Larry Harris at the University of New Hampshire in 2018 and the University of Rhode Island in 2019.

Disclosure statement

No potential conflict of interest was reported by the author(s).