Open Collections

Askelson, Kenneth

University of British Columbia

Understanding how selection, recombination, and introgression interact during the speciation process is a key goal in the field of evolution, and many questions remain unanswered. In my dissertation, I make use of a cryptic species complex of white-breasted nuthatches (Sitta carolinensis) to understand the landscape of genomic differentiation between these putative species and how recombination and introgression have shaped those patterns. I then extend my findings regarding recombination and differentiation in white-breasted nuthatches to examine a broad sampling of genomic differentiation in avian species pairs, to infer how chromosome length (and thus rates of recombination) have shaped genome-wide patterns of differentiation. Through my research, I found that white-breasted nuthatches are comprised of four differentiated populations that are on a continuum of differentiation and that ghost lineage introgression has been involved in shaping these patterns. I also found evidence for large inversion-like haploblocks occurring in white-breasted nuthatches. I then combined these differentiation patterns with recombination estimates to show that broad-scale recombination rates are negatively associated with differentiation. In my final chapter, I found that the relationship between differentiation and chromosome length varied among pairs, but the direction of this relationship was significantly negatively correlated with the age of divergence. This result points to large chromosomes with lower rates of recombination being the likely areas to have higher amounts of differentiation in younger species. My dissertation spans a wide research scope, from species-specific questions to broad questions about recombination and differentiation. It expands our knowledge of bird species by describing the genomic patterns of this cryptic species complex and how ghost lineage introgression has provided important variation. My research also advances the field by adding to the growing body of evidence that areas of low recombination are associated with regions of increased differentiation and that these landscapes of recombination likely shape genomic differentiation across bird species.

Text

2023-12-18

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/86976

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/