Phylogenetically diverse introgression drives subtle population structure in Pacific rockfishes

Area of Science:

• Marine biology
• Genomics
• Evolutionary biology

Background:

• Admixture and introgression are prevalent in animal populations.
• Pacific rockfishes (genus *Sebastes*) are commercially important species along the North American west coast.
• Copper and Quillback Rockfishes are closely related and known to hybridize, especially in the Salish Sea.

Purpose of the Study:

• To compare population genetic structure between Copper and Quillback Rockfishes.
• To assess the impact of introgression on population structure patterns.
• To investigate range-wide genetic patterns and introgression in these species.

Main Methods:

• Whole-genome resequencing (WGS) was employed across a broad geographic range.
• Population genetic structure was analyzed for Copper and Quillback Rockfishes.
• Introgression patterns were identified from multiple rockfish species.

Main Results:

• Copper Rockfish showed higher population differentiation than Quillback Rockfish, with Salish Sea samples distinct.
• Quillback Rockfish populations were largely panmictic with low differentiation.
• Significant introgression from 13 (Copper) and 16 (Quillback) other rockfish species was detected, varying regionally.
• Yelloweye Rockfish introgression strongly influenced Quillback population structure.

Conclusions:

• Copper and Quillback Rockfishes exhibit different population structures and levels of differentiation.
• Hybridization in *Sebastes* is more extensive and phylogenetically diverse than previously understood.
• Introgression patterns are geographically dependent, influenced by congener ranges and local context.