Abstract

BackgroundAlthough polychaetes are one of the dominant taxa in marine communities, their distributions and taxonomic diversity are poorly understood. Recent studies have shown that many species thought to have broad distributions are actually a complex of allied species. In Canada, 12% of polychaete species are thought to occur in Atlantic, Arctic, and Pacific Oceans, but the extent of gene flow among their populations has not been tested.Methodology/Principal FindingsSequence variation in a segment of the mitochondrial cytochrome c oxidase I (COI) gene was employed to compare morphological versus molecular diversity estimates, to examine gene flow among populations of widespread species, and to explore connectivity patterns among Canada's three oceans. Analysis of 1876 specimens, representing 333 provisional species, revealed 40 times more sequence divergence between than within species (16.5% versus 0.38%). Genetic data suggest that one quarter of previously recognized species actually include two or more divergent lineages, indicating that richness in this region is currently underestimated. Few species with a tri-oceanic distribution showed genetic cohesion. Instead, large genetic breaks occur between Pacific and Atlantic-Arctic lineages, suggesting their long-term separation. High connectivity among Arctic and Atlantic regions and low connectivity with the Pacific further supports the conclusion that Canadian polychaetes are partitioned into two distinct faunas.Conclusions/SignificanceResults of this study confirm that COI sequences are an effective tool for species identification in polychaetes, and suggest that DNA barcoding will aid the recognition of species overlooked by the current taxonomic system. The consistent geographic structuring within presumed widespread species suggests that historical range fragmentation during the Pleistocene ultimately increased Canadian polychaete diversity and that the coastal British Columbia fauna played a minor role in Arctic recolonization following deglaciation. This study highlights the value of DNA barcoding for providing rapid insights into species distributions and biogeographic patterns in understudied groups.

Highlights

  • Molecular tools are increasingly recognized as necessary for delineating species boundaries, quantifying diversity, and clarifying distributions in understudied groups [1,2,3]

  • We evaluate the utility of DNA barcoding for discriminating polychaete species, compare richness estimates based on morphological versus molecular taxonomy, examine the genetic structure of widespread species, and investigate broad-scale connectivity patterns among the oceans surrounding Canada

  • Amplification success Three primer sets successfully amplified the barcode region of c oxidase I (COI) from 1876 of 2324 specimens (81% success)

Read more

Summary

Introduction

Molecular tools are increasingly recognized as necessary for delineating species boundaries, quantifying diversity, and clarifying distributions in understudied groups [1,2,3] These tools can be useful in marine systems where there is a poor understanding of species boundaries and broad-scale distributions. Polychaetes are an abundant and speciose group in marine systems yet they are little studied compared to other taxa of similar ecological importance [8] Despite their ubiquity (over 10,000 described species [9,10,11]), polychaetes have generally been excluded from broad-scale distributional studies because of their supposed lack of geographic structure [12,13,14]. In Canada, 12% of polychaete species are thought to occur in Atlantic, Arctic, and Pacific Oceans, but the extent of gene flow among their populations has not been tested

Methods
Results
Discussion
Conclusion

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.