Costly Courtship: Condition Dependence of a Multimodal Courtship Signal in a Parasitoid Wasp

Signals that mediate mating decisions are often considered to be condition dependent and therefore function as a cue for an individual's quality. However, much of this research has focused on a single signal modality. But despite the additional cost associated with the use of multiple modalities, multimodal courtship signals are common in animals. Therefore, it is important to consider all modalities when assessing if a multimodal courtship signal is condition dependent.

Here, we test whether the two components of the multimodal courtship of the parasitoid wasp, Leptopilina heterotoma, are condition dependent. L. heterotoma male courtship consists of a chemical signal (cuticular hydrocarbons (CHCs)) and a vibratory signal (wing fanning). Previous research has shown that larger males and males with a higher fundamental frequency when wing fanning are more likely to mate. However, there was no difference in the CHC profile between successful and unsuccessful males. To determine if any of these signals are affected by a male's condition, we manipulated the males in two ways (nutritional state and age) and then conducted courtship trials. During the courtship we recorded the wing fanning frequency with a laser Doppler vibrometer and analyzed the male CHC profiles using gas chromatography–mass spectroscopy (GC-MS).

We show that male CHC profiles differ depending on male condition in both, the nutritional stage and age treatments. The analysis of our wing fanning data is still in progress. However, previous research suggests that the starved and older males have a lower fundamental frequency wing fanning compared to their fed and young counterparts. Therefore, it is likely that all elements of L. heterotoma's courtship signal are condition-dependent and may serve as a cue of individual quality.