| dc.description.abstract | Sexual isolation occurs between Drosophila simulans and D. sechellia due to differences in cuticular hydrocarbon (CHC) productions. A wide variety of hydrocarbons are produced, but D. simulans males and females predominantly produce 7-tricosene (7-T), a 23 carbon monoene, while D. sechellia males produce 7-T and D. sechellia females produce 7,11-heptacosadiene (7,11-HD), a 27 carbon diene (Coyne et al. 1994). An asymmetric mating pattern occurs due to hydrocarbon differences: D. simulans males only court D. simulans females and D. sechellia males court both D. simulans and D. sechellia females (Cobb and Jallon 1990). Previous quantitative trait locus (QTL) studies (Gleason et al. 2005; Gleason et al. 2009) identified desatF and eloF as candidate genes contributing to production of D. sechellia pheromone 7,11-HD. In this thesis, the effect of D. sechellia alleles in a D. simulans background is measured for desatF and eloF by (1) monitoring mating behavior response through copulation success and latency and (2) identifying the differences in CHC biosynthesis through elongation and desaturation changes. Behavioral analyses indicated that there was no significant effect on courtship for the genes independently. Analysis of CHC production differences indicates a more pronounced effect of desatF and eloF on pheromone biosynthesis. In elongation from 23 to 25 carbons, females carrying the eloF gene produced increased amounts of 7-pentacosene, indicating eloF effects hydrocarbon elongation. Absence of further elongation to 27 carbons suggests involvement of other elongases for synthesis to 7,11-HD. Females carrying the desatF gene produced increased amounts of 7,11-pentacosadiene, indicating desatF is responsible for increasing dienes. Only when females carried D. sechellia alleles at both loci did production of 7,11-HD occur. However, the amount of 7,11-HD was significantly lower than amounts produced by D. sechellia females. Evidence from this study indicates desatF and eloF are genes present in the hydrocarbon biosynthesis pathway and are probably necessary for female D. sechellia pheromone production. However, D. sechellia alleles of desatF and eloF are not sufficient for production of 7,11-HD indicating involvement of other biosynthesis genes to fully produce the D. sechellia female pheromone. | |
