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A Method to Test the Effect of Environmental Cues on Mating Behavior in Drosophila melanogaster
Published on: July 17, 2017
Evolutionary basis of intermale sexual behavior by multiple pheromone switches in Drosophila
Youcef Ouadah1, Thomas H Naragon2, Hayley Smihula2
1Division of Biology and Biological Engineering, Tianqiao and Chrissy Chen Institute for Neuroscience, and Howard Hughes Medical Institute, Caltech; Pasadena, CA, USA.
Insights
Male fruit flies (Drosophila) show strong intermale courtship due to evolved changes in pheromones. These chemical signals, like cVA, influence mating behavior and species recognition, impacting evolution.
Area of Science:
- Evolutionary biology
- Animal behavior
- Neuroethology
Background:
- Intermale sexual behavior is observed in some Drosophila species.
- Pheromones play a crucial role in regulating insect mating behaviors.
- Understanding the genetic and chemical basis of behavior is key to evolutionary studies.
Purpose of the Study:
- To investigate the evolutionary mechanisms behind robust intermale sexual behavior in Drosophila santomea.
- To identify the specific pheromonal changes contributing to altered courtship in D. santomea.
- To explore the role of pheromonal valence shifts in the evolution of social behavior.
Main Methods:
- Behavioral assays to quantify intermale courtship.
- Gas chromatography-mass spectrometry (GC-MS) to analyze cuticular hydrocarbon profiles.
- Comparative analysis of pheromone levels and behavioral responses across related species.
Main Results:
- Drosophila santomea males exhibit vigorous intermale courtship and reduced aggression.
- Key pheromonal changes include increased 7-tricosene and significantly reduced cis-vaccenyl acetate (cVA) in males.
- D. santomea females show aversion to cVA, contrasting with related species.
Conclusions:
- Evolutionary shifts in pheromone perception and production drive the emergence of intermale sexual behavior.
- Co-evolution of female cVA aversion and male cVA reduction likely prevents hybridization.
- Pheromonal convergence in D. persimilis suggests similar evolutionary pathways for social behavior.
Abstract:
We have identified a Drosophila species which exhibits spontaneous and robust intermale sexual behavior. D. santomea males distinguish conspecific sexes but court both vigorously and seldom attack. Elevated intermale courtship stems from at least three evolutionarily derived pheromonal changes. In males, the sexually monomorphic cuticular pheromone 7-tricosene promotes rather than inhibits courtship and the courtship-inhibiting olfactory pheromone cVA is reduced 84-92% compared to close relatives. The third switch is in D. santomea females, where cVA suppresses rather than promotes sexual receptivity. Female cVA aversion and male cVA reduction may have co-evolved to maintain efficient intraspecific mating but prevent hybridization with the sympatric sibling species D. yakuba. High intermale courtship and low cVA also co-occur and appear selectively derived in a distant monomorphic species D. persimilis, implying pheromonal and social behavioral convergence. Changes in pheromone valence and levels may therefore explain the recent evolutionary emergence of intermale sexual behavior in Drosophila.
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