From Genes to Behavior: A Cross-Species Analysis of Courtship Song Production and Evolution in Drosophila

Abstract

Acoustic communication is utilized for mate attraction in Drosophila melanogaster during its innate courtship behavior. Investigations of this model organism's courtship song have revealed the underlying neurogenetic mechanisms. However, the Drosophila genus, as a whole, displays a rich diversity of species-specific courtship songs. The mechanisms underlying these evolved behaviors remain unknown. Here, I explore the genetic and neural basis of courtship song production and evolution in three Drosophila species: D. yakuba, D. santomea and D. virilis.

In the first study, I investigate the divergence of a courtship song parameter between D. yakuba and D. santomea using new methods for estimating genomic ancestry. Through Quantitative Trait Locus mapping, I demonstrate that the evolution of this single parameter involves at least three genes of additive effect. We confirm the predicted phenotypic effects, while minimizing the genomic region of interest, through introgression mapping.

In the second study, I characterize male and female courtship song interactions in Drosophila virilis. By quantifying these acoustic signals via a high throughput behavioral assay, I demonstrate that males and females coordinate their songs in an acoustic duet. By manipulating the sensory inputs to the female, I reveal the role of tactile cues in female song production and timing. These data uncover a novel, non-acoustic mechanism for duetting. Finally, by comparing duets produced in male-male pairings, I show that D. virilis "female" song production circuits are not sexually dimorphic.

I aim to understand the neural circuit basis for female song production and coordination in D. virilis, so in the final study, I test methods for generating neurogenetic tools in this species. I explore two genome-editing strategies for manipulating the D. virilis fruitless locus and describe the generation of enhancer-fusion constructs to drive expression of visual markers in the D. virilis nervous system.

The work presented here provides the first quantitative data on song evolution between D. yakuba and D. santomea and song production in D. virilis. My results demonstrate the power of using quantitative approaches to study behavior across a broad range of species and provide novel insights into the causal mechanisms of Drosophilid acoustic communication.