A Tri-Oceanic Perspective: DNA Barcoding Reveals Geographic Structure and Cryptic Diversity in Canadian Polychaetes

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.

LifeWatchGreece: Research infrastructure (ESFRI) for biodiversity data and data observatories

“…Fauvel (1927), comprise a wide variety of characters and probably comprise more than one species under this name . Likewise, molecular analyses by Carr et al (2011) revealed at least two putative cryptic species in Canadian waters (one in the Arctic, another in the Pacific Ocean) which were initially identified as Bradabyssa villosa. restricts Bradabyssa villosa sensu stricto to the North Atlantic Ocean and European and Russian Arctic and re-instates Bradabyssa parthenopeia (Lo Bianco, 1893) from the Mediterranean (Gulf of Naples) -a species previously considered a synonym of Bradabyssa villosa.…”

“…Consists of at least two different putative cryptic species in the Arctic Ocean (Carr et al 2011), specimens from other locations could belong to either of these or to a different cryptic species. considers the distribution of Flabelligera affinis to be restricted to "Arctic to cold and temperate, boreal localities" and questions the identity of specimens reported under this name from warm water localities such as Africa or Panama.…”

“…Notes: Reported from Greece by Tselepides (1992 (Carr et al 2011) and another in Portugal (Lobo et al 2016). …”

Phylogenetic Relationships of Twenty-One Nereids Species Inferring Two Different Evolutionary Origins?

“…With the rapid development of molecular tools, they have been recognized as necessary for delineating species boundaries, quantifying diversity, and clarifying distributions in understudied groups (Westheide & Schmidt, 2003;Carr et al, 2011). Mitochondrial DNA (mtDNA) has been applied widely in the studies of phylogenetics and evolution as well as an effective marker to assist taxonomy because of its uniparental inheritance (in a majority of animal phyla), high evolutionary rate, lack of introns, large copy numbers in every cell, and limited recombination (Adriana et al, 2010).…”

A new evolutionary unit in the Excirolana braziliensis species complex

“…Several cases of cryptic species have been reported for marine species with relatively wide geographical range and low dispersal potential (BAIRD et al, 2011;BOISSIN et al, 2008;CARR et al, 2011;HELD;WÄGELE, 2005;LARSEN et al, 2014;MARKOW;PFEILER, 2010;RAUPACH et al, 2007;REMERIE et al, 2006;SPONER;LESSIOS, 2009;VARELA;HAYE, 2012;XAVIER et al, 2016). In a low dispersal scenario, as in many marine brooders, isolation by distance and outbreeding depression are enough to account for a high speciation rate (HOELZER et al, 2008).…”