Sex Pheromone Mediates Resource Partitioning Between <i>Drosophila melanogaster</i> and <i>D. suzukii</i>

The spotted-wing drosophila, <i>Drosophila suzukii</i> and the cosmopolitan vinegar fly <i>D. melanogaster</i> feed on soft fruit and berries and widely overlap in geographic range. The presence of <i>D. melanogaster</i> reduces egg-laying in <i>D. suzukii</i>, possibly because <i>D. melanogaster</i> outcompetes <i>D. suzukii</i> larvae feeding in the same fruit substrate. Flies use pheromones to communicate for mating, but pheromones also serve a role in reproductive isolation between related species. We asked whether a <i>D. melanogaster</i> pheromone also modulates oviposition behaviour in <i>D. suzukii</i>. A dual-choice oviposition assay confirms that <i>D. suzukii</i> lays fewer eggs on blueberries exposed to <i>D. melanogaster</i> flies and further shows that female flies have a stronger effect than male flies. This was corroborated by treating berries with synthetic pheromones. Avoidance of <i>D. suzukii</i> oviposition is mediated by the female <i>D. melanogaster</i> pheromone (<i>Z</i>)-4-undecenal (Z4-11Al). Significantly fewer eggs were laid on berries treated with synthetic Z4-11Al. In comparison, the male pheromone (<i>Z</i>)-11-octadecenyl acetate (cVA) had no effect on <i>D. suzukii</i> oviposition. Z4-11Al is a highly volatile compound that is perceived via olfaction and it is accordingly behaviourally active at a distance from the source. <i>D. suzukii</i> is known to engage in mutual niche construction with the yeast <i>Hanseniaspora uvarum</i>, which strongly attracts flies. Adding Z4-11Al to fermenting <i>H. uvarum</i> significantly decreased <i>D. suzukii</i> flight attraction in a laboratory wind tunnel and a field trapping assay. That a <i>D. melanogaster</i> pheromone regulates oviposition in <i>D. suzukii</i> demonstrates that heterospecific pheromone communication contributes to reproductive isolation and resource partitioning in cognate species. Stimulo-deterrent diversion or push-pull methods, building on combined use of attractant and deterrent compounds, have shown promise for control of <i>D. suzukii</i>. A pheromone that specifically reduces <i>D. suzukii</i> attraction and oviposition adds to the toolbox for <i>D. suzukii</i> integrated management.