Genetic assignment of fisheries bycatch reveals disproportionate mortality among Alaska Northern Fulmar breeding colonies

Species delimitation using genomic data to resolve taxonomic uncertainties in a speciation continuum of pelagic seabirds

Speciation is a continuous and complex process shaped by the interaction of numerous evolutionary forces. Despite the continuous nature of the speciation process, the implementation of conservation policies relies on the delimitation of species and evolutionary significant units (ESUs). Puffinus shearwaters are globally distributed and threatened pelagic seabirds. Due to remarkable morphological status the group has been under intense taxonomic debate for the past three decades. Here, we use double digest Restriction-Site Associated DNA sequencing (ddRAD-Seq) to genotype species and subspecies of North Atlantic and Mediterranean Puffinus shearwaters across their entire geographical range. We assess the phylogenetic relationships and population structure among and within the group, evaluate species boundaries, and characterise the genomic landscape of divergence. We find that current taxonomies are not supported by genomic data and propose a more accurate taxonomy by integrating genomic information with other sources of evidence. Our results show that several taxon pairs are at different stages of a speciation continuum. Our study emphasises the potential of genomic data to resolve taxonomic uncertainties, which can help to focus management actions on relevant taxa, even if they do not necessarily coincide with the taxonomic rank of species.

Fine-scale population genetic structure and barriers to gene flow in a widespread seabird (Ardenna pacifica)

Pelagic seabirds are highly mobile, reducing opportunities for population isolation that might promote differentiation and speciation. At the same time, many seabirds are philopatric, and their tendency to return to their natal islands to breed might reduce gene flow sufficiently to permit local adaptation and differentiation. To test the net impact of these competing processes, estimates of differentiation and gene flow based on comprehensive geographical sampling are required. We leveraged diverse source material to achieve comprehensive geographical sampling in a widespread seabird, the Wedge-tailed Shearwater (Ardenna pacifica). Using data from sequence capture and high-throughput sequencing of 2402 loci containing 20 780 single nucleotide polymorphisms, we tested for population differentiation and gene flow among breeding areas. We found little evidence of deep divergences within A. pacifica but were able to resolve fine-scale differentiation across island groups. This differentiation was sufficient to assign individuals sampled away from breeding areas to their likely source populations. Estimated effective migration surfaces revealed reduced migration between the Indian Ocean and Pacific Ocean, presumably owing to land barriers, and across the equatorial Pacific Ocean, perhaps associated with differences in breeding schedule. Our results reveal that, despite their mobility, pelagic seabirds can exhibit fine-scale population differentiation and reduced gene flow among ocean basins.