Cost of pheromone production in a lekking Drosophila

'Sex pheromones' are most commonly seen as mate attraction signals. However, there is growing evidence that chemical signals may also advertise mate quality. Theory predicts that for mate quality signals to be reliable they should be costly, a mechanism that is likely to drive condition-dependent expression of the signal in question. We investigated the relation between pheromone production and life span in Drosophila grimshawi, a lekking fruit fly where males deposit pheromones on the lekking arena. We manipulated pheromone production by subjecting males to another male, a female or no companion twice a week for the duration of their adult lives. We found that long-lived males deposited pheromones for a greater proportion of their lives across treatments. Males that met other males, rather than females or no flies, also deposited pheromones for a greater proportion of their lives. However, this greater investment seemed to be costly since these males also had shorter life spans, presumably as a result of increased pheromone production. Thus, our results support the notion that pheromone production may act as an honest signal of quality. Furthermore, we show that the pheromone has multiple functions and that male D. grimshawi appear to adjust their investment in pheromone production in relation to their social environment.