Date of Completion


Document Type

Honors College Thesis


Plant Biology

Thesis Type

Honors College

First Advisor

Stephen R. Keller


Introgression, hybridization, admixture, Populus, stress resistance


Introgression is known from many natural populations of plants for its potential for fitness effects in response to changing environments. Genomic footprints of admixture exist in Populus trichocarpa with its sister species, Populus balsamifera due to its natural hybrid zones in Alaska, northwestern Canada, and the Canadian Rockies. The relationship between admixture and phenotypic variations was investigated with experimental crosses between related species of Populus to determine whether the admixed offspring demonstrates hybrid vigor and increased stress-resistance. Additionally, the presence of candidate genes and loci was investigated for adaptive introgression, where a region associated with the trait of interest is heterozygous for P. trichocarpa and P. balsamifera alleles. Experimental offspring were generated by crossing male genotypes containing various ancestry fractions of these two species (from 0% P. balsamifera up to 7% P. balsamifera) with female genotypes of other species used in poplar breeding programs. The resulting offspring were then subjected to a factorial stress experiment of heat and drought in controlled growth chambers. The results demonstrated that a combination of these stressors significantly affected stomatal conductance in offspring from both admixed and non-admixed ancestries. Local ancestry inferences revealed the presence of genomic regions in the parent species associated with stomatal conductance and stomatal density. The study provides insights into the genetic basis of stress resilience in admixed plant populations which could be crucial to understand for conservation and management efforts in the face of climate change.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.