Graduation Year

2023

Graduation Month

May

Document Type

Thesis

Degree Name

Bachelor of Science

School or Department

Wildlife Biology

Major

Wildlife Biology – Terrestrial

Faculty Mentor Department

Biological Sciences, Division of

Faculty Mentor

Zac Cheviron

Keywords

chickadee, hybrid zone, genes, introgression, hybridization, fitness

Subject Categories

Genomics

Abstract

Hybridization between species plays a very important role in the overall evolutionary history of many taxa. The study of hybrid zones can also provide insight into how species are responding to environmental factors such as climate change and changes in species interactions. The hybrid zone between the northern black-capped chickadee (Poecile atricapillus) and the southern Carolina chickadee (Poecile carolinensis) provides an insight into how hybridization is affecting two distinct species. Black-capped and Carolina hybrids have reduced fitness in the wild. Hybrids tend to have higher basal metabolic rates, less muscle growth, and less neuron growth to prepare for winter caching. Locus-specific patterns of introgression can be used to identify loci that may contribute to species boundaries and fitness reduction in hybrids. Specifically, alleles that fail to introgress across hybrid zones could give an insight into why hybrids have reduced fitness. Our goal was to look at what functions those genes may have, and to see if the genes that don’t introgress exhibit higher sequence divergence than those that do. We used mRNA transcript sequences generated from both black-capped and Carolina chickadees to determine whether loci that exhibit reduced introgression across the hybrid zone also show elevated sequence divergence compared to a sample of random genes, and whether these genes participate in key physiological processes. We calculated the mean percent sequence divergence for both the top ten non-introgressing genes and the ten randomly selected genes. The non-introgressing genes exhibited significantly higher sequence divergence than the random genes (p=0.0169). This result demonstrates loci that fail to introgress have higher levels of sequence divergence than random genes. This suggests that there might be functional differences between species in the genes that could contribute to reduced fitness in hybrids.

Honors College Research Project

1

GLI Capstone Project

no

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