Genomic Insights Into the Molecular Basis of Sexual Selection in Birds

Shubham K Jaiswal,Ankit Gupta,Vineet K Sharma,Vishnu Prasoodanan P K,Nagarjun Vijay,Aaron B A Shafer

doi:10.3389/fevo.2021.538498

Shubham K Jaiswal, Ankit Gupta + Show 4 more

Open Access

https://doi.org/10.3389/fevo.2021.538498

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Abstract

Sexual selection is a well-known biological process, yet the genomic basis and patterns of sexual selection are not fully understood. The extravagant ornamental plumage of peacock (Pavo cristatus) was instrumental in shaping Charles Darwin's theory of sexual selection and is considered to be an honest signal of its immunocompetence. Here, we used the recently generated draft genome sequence of peafowl (Pavo cristatus) and carried out a comparative analysis across 11 bird genomes that encompass a range of sexual selection and also had high-quality genomic and phenotypic data publically available to study the genomic basis of sexual selection. We found that varying degree of purifying selection was the predominant mechanism of action for sexual selection at the genome-wide scale and observed that sexual selection mostly influences genes regulating gene expression and protein processing. Specifically, the genome-wide phylogenetically corrected regression analysis supported the continuous or ongoing model of sexual selection. Genes involved in nucleic acid binding and gene expression regulation, including a specific regulator of sex-determination known as TRA2A to be under positive selection in the species with high post-copulatory sexual selection manifested as high sperm competition. We also detected specific feather-related and immune-related gene-pairs evolving under similar selection pressures across the 11 species, including peacock (Pavo cristatus), which is consistent with the Hamilton-Zuk hypothesis. The comparative genomics analysis of 11 avian taxa has provided new insights on the molecular underpinnings of sexual selection and identifies specific genomic regions for future in-depth analysis.

Highlights

Sexual selection is a mode of natural selection where increased reproductive success is achieved through adaptations that either attract females or help outcompete other males
We used relative testis weight as a proxy phenotype for post-copulatory sexual selection manifested as sperm competition, whereas dichromatism score was used as the proxy phenotype for precopulatory sexual selection manifested as plumage dimorphism (Supplementary Tables 1, 2)
The analysis of the coding genome for 11 high-quality bird species, which display a broad range of sexual selection allowed us to reveal the genomic signatures of sexual selection in birds

Summary

Introduction

Sexual selection is a mode of natural selection where increased reproductive success is achieved through adaptations that either attract females or help outcompete other males. Birds (Class Aves) have been the model organisms for studying sexual selection, with the classic example being the plumage patterns and large tail-coverts of peacock (Pavo cristatus). It was, Charles Darwin’s fascination with the peacock that shaped his theory of sexual selection (Darwin, 1872, 1896, 1911). In peacock the mating success has been highly correlated with the coloration and length of feather train (Petrie and Williams, 1993; Loyau et al, 2007) which implies that ornamental plumage traits in birds are a consequence of sexual selection

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