Hybridization dynamics and population genomics of a Manacus hybrid zone

Long, Kira Michelle

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https://hdl.handle.net/2142/121307 Copy

Description

Title

Hybridization dynamics and population genomics of a Manacus hybrid zone

Author(s)

Long, Kira Michelle

Issue Date

2023-06-16

Director of Research (if dissertation) or Advisor (if thesis)

Brawn, Jeffrey D

Doctoral Committee Chair(s)

Brawn, Jeffrey D

Committee Member(s)

• Fuller, Rebecca C
• Catchen, Julian M
• Braun, Michael J

Department of Study

School of Integrative Biology

Discipline

Ecol, Evol, Conservation Biol

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• manakin
• hybridization
• population genomics
• fitness
• evolutionary biology

Abstract

Hybrid zones form where two species meet and interbreed. Understanding how these zones change over space and time is integral to understanding speciation events, where species originate from diverging populations that can still interbreed. This work focuses on the dynamics of hybridization in two species of tropical birds, in which females come to leks to assess males that compete to attract females, resulting in strong sexual selection on male traits. In this hybrid zone of the golden-collared manakin (Manacus vitellinus) and white-collared manakin (Manacus candei), females prefer males with yellow throat plumage, leading to a historical spread of yellow M. vitellinus coloration into white M. candei populations. In this hybrid zone I investigate: 1) if there is any detectible movement in this hybrid zone over time, 2) what are the consequences of hybridization on hybrid fitness, and 3) what are the genomic patterns of hybridization and incompatibilities in hybrid genomes. To assess spatial dynamics in the hybrid zone, I resampled this system using large-scale genomic data 30 years after the original study using both historical and modern genetic samples from across the hybrid zone. This sampling scheme allowed for a direct comparison of genetic markers across space and time, making this study a rare opportunity to directly observe how hybridizing genomes interact, and uncover underlying mechanisms of ongoing evolution. I found that this hybrid zone is largely spatially stable with the genomic center in the same location as when the hybrid zone was first assessed, and that M. vitellinus yellow plumage has not continued to spread. However, I found evidence of olive belly color from male M. vitellinus continuing to introgress over time, suggesting that sexual selection is an ongoing evolutionary force shaping this system. One mechanism for the observed stability at the genomic center in this system could be from natural selection against hybrids. Accordingly, I investigated two components of fitness, survival rates and egg hatching rates, and assessed the importance of a possible selective pressure - prevalence of Haemosporidian parasites. Estimated apparent survival rates were similar between parental and hybrid populations and infection by Plasmodium or Haemoproteus parasites was limited to only 1.5% of the 268 birds sampled. Hatching failure, however, was more likely in hybrid nests when compared to parental nests, with 70% of hybrid nests having 1 or more eggs fail to hatch. Lastly, given that selection against hybrids appears to manifest in the developmental stages, I investigated patterns of genetic incompatibilities in hybrid genomes, looking at patterns of genetic divergence, linkage disequilibrium, and distribution of parental alleles in hybrid genomes. I found that hybrids from the genomic center of the hybrid zone had drastically elevated signatures of linkage disequilibrium, implying that the absence of recombination and/or selection against alleles introduced to the new genomic background in hybrids is preventing the complete mixing of parental haplotypes. I also found that the avian homogametic sex chromosome (Z-chromosome) had distinct patterns from the other autosomes, with elevated genetic divergence, extended linkage disequilibrium, and disparate proportions of parental alleles, in turn implicating the Z-chromosome as a major driver of selection against hybrids. Overall, this work takes a comprehensive look at the hybridization dynamics of this hybrid zone, combining extensive field observations, next generation sequencing, and bioinformatics to uncover the complex interplay of ecology, selection, and genome architecture in hybrid systems.

Graduation Semester

2023-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Kira M. Long

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