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Topic

Introgression and subtle population structure in threatened Pacific rockfishes

Department of Biology

Date & location

• Friday, December 6, 2024
• 2:00 P.M.
• Clearihue Building, Room B007

Examining Committee

Supervisory Committee

• Dr. Greg Owens, Department of Biology, University of Victoria (Supervisor)
• Dr. Ben Koop, Department of Biology, UVic (Member)
• Dr. John Taylor, Department of Biology, UVic (Member)

External Examiner

• Dr. Rick Taylor, Department of Zoology, University of British Columbia

Chair of Oral Examination

• Dr. Kieka Mynhardt, Department of Mathematics and Statistics, UVic

Abstract

Genomic methods are increasingly being applied in fisheries to promote effective management and sustainability. Pacific rockfishes, genus Sebastes, inhabit nearshore and coastal shelves along the North American west coast. Among these, copper and quillback rockfishes constitute a species complex (along with brown rockfish) which are known to hybridize, particularly within the Salish Sea. Here, we investigate genetic population structure and introgression patterns in copper and quillback rockfish. Using low-coverage whole-genome resequencing (lcWGS) across a broad geographic range, we seek to (1) describe genetic differentiation between the sibling species, (2) assess population structure within each species, (3) identify regions of the genome with unique patterns of relatedness between species, and (4) look for signatures of introgression in the genomes of both species. Our analyses reveal that copper rockfish exhibit higher levels of population differentiation compared to quillback, especially between coastal and Salish Sea populations. In contrast, quillback populations appear to be more panmictic, with lower overall differentiation. Several large haploblocks are found to be segregating between the species, with introgression patterns varying across genomic regions. These findings provide novel insights into the range-wide genetic structure of these species and highlight the role genomic architecture in local introgression. The results have important implications for the conservation and management of these overharvested species.