Distinct roles for expression of vasoactive intestinal peptide in the behavioral polymorphism in white-throated sparrows (Zonotrichia albicollis) Restricted; Files Only
Prichard, Mackenzie R. (Fall 2023)
Abstract
Understanding how behavioral traits are inherited and, to some extent, genetically encoded is critical to understanding how behavior evolves. Investigating the genetic basis of behavior is often challenging because behavioral traits are highly plastic and multiply determined. Model organisms that carry supergenes have garnered attention for their utility in this pursuit. One such organism is the white-throated sparrow (Zonotrichia albicollis), which stands out among others because half the population carries one of the largest chromosomal inversions, or supergenes, discovered to date. This supergene forms the basis of a behavioral polymorphism that represents a life history trade-off; individuals with the supergene are more aggressive and less parental than those without it. In this study, I looked for evidence that the neuromodulator vasoactive intestinal peptide (VIP), which is encoded by a gene inside the supergene, is associated with multiple aspects of the behavioral polymorphism in white-throated sparrows. Previous research in other avian species demonstrated that VIP in the anterior hypothalamus (AH) promotes aggression, whereas VIP released by neurons in the infundibular nucleus (IN) controls the secretion of prolactin, a parenting hormone. Here, I demonstrate that expression of VIP mRNA in the AH is greater in birds that carry the supergene than in those that do not and that in the IN, the birds that do not carry the supergene have higher levels of expression than those that do. I show that the supergene allele of VIP is expressed more than the standard allele in both brain regions, but the degree that the supergene allele is overexpressed is greater in the AH than in the IN. I also demonstrate that both the level of VIP expression overall and the degree to which the supergene allele is overexpressed in the AH and the IN predict aggression and parental care, respectively. I conclude by discussing several mechanisms that could affect VIP expression and propose how VIP may interact with larger neural and gene expression networks that mediate life history trade-offs.
Table of Contents
List of Tables i
List of Figures ii
List of Symbols and Abbreviations iii
Introduction 1
Results 8
Discussion 16
Methods 27
References 38
Figures 57
Appendix 69
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File download under embargo until 10 January 2025 | 2023-12-17 19:03:03 -0500 | File download under embargo until 10 January 2025 |
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