Natural variation and gene expression in the male courtship progression of Drosophila melanogaster

Natural genetic variation in the temporal sequence of male courtship behavior can be one target of selection. The goals of this research were to identify variation in the sequence of male behavior using a natural population, and investigate the genetic underpinnings of this variation. A new, high-throughput method of male courtship analysis is presented; this method focuses on the progression of male courtship over time (MCP), and is more sensitive than previously used metrics of measurement. This method was used to examine differences in MCP between males from full-sibling families, using either virgin or previously mated females as targets. There were significant genetic differences in MCP for families placed with either female targets, and hence there was natural genetic variation for MCP in that population. To investigate the genetic underpinnings of this behavioral variation, previously identified male courtship candidate genes were examined for alterations in expression due to changes in age or experience. Expression changes across the entire genome associated with differences in MCP were then investigated to determine if previously identified candidates were also involved in natural behavioral variation. Candidate courtship genes identified from previous research were examined for non-genotypic changes in gene expression using genetically identical males of different ages, with different levels of exposure to females. These genes had altered expression due to age (reproductive maturity) but not experience with a female. Microarray analysis was then used to determine which genes exhibited differential baseline expression between mature males from families with the most extreme differences in MCP from the previous experiment. Fourteen candidate genes were identified as being differentially expressed, and none of these had been previously associated with male courtship behavior. Potential roles for these fourteen new candidates were suggested, and a factor pattern analysis revealed that several of them might be co-regulated. The culmination of this research brings us one step closer to understanding the genetic basis for natural behavioral variation in male courtship; this information can now be used to determine what sequence differences are associated with expression differences in candidate genes, and how selection might be acting on this variation.