Sexual Selection

Sexual selection through pheromones in the wood tiger moth

In a Nutshell

Moths are well-known for releasing sex pheromones from a gland situated at the tip of their abdomen, usually after sunset or during the night. These molecular blends signal attraction to conspecifics and aid mate selection.

The traditional view is that sex pheromones are important for discriminating between different moth species and thereby targeting the right mating partners. Thus, sex pheromone signals are not expected to vary much within species. The current pheromone literature, however, is showing that sex pheromones can be quite variable within species and potential mates are selective in their appetites. Therefore, variation in sex pheromones can affect mate choice and, consequently, gene flow between individuals and populations.

This suggests that sex pheromone variation may be involved in population divergence and ultimately affect species evolution (see our review in TREE).

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Key Papers

  • De Pasqual C., Groot A.T., Mappes J., Burdfield-Steel E. (2021) “Evolutionary Importance of Intraspecific Variation in Sex Pheromones”. TREE – in press

One signal, multiple functions

How a sex pheromone may simultaneously affect within- and between-populations dynamics

We are currently exploring the role of sex pheromone variation in the maintenance of wood tiger moth polymorphism (white or yellow hindwings).

Mate choice studies suggest that sex pheromones are related to female attractiveness and biases in male preferences. So we are investigating how this relates to the type and amount of chemicals in the pheromone blend, alongside behavioral components such as calling.

Regardless of the underlying mechanism, we have discovered that ‘preferred’ females carry allele combinations that produce yellow males, whilst ‘less-preferred’ females carry alleles that code for white males. There may be elements of an evolutionary trade-off here, as preferred females tend to have lower reproductive output than less-preferred females.

In parallel, we are currently investigating the role of pheromone variation in the ongoing divergence between wood tiger moth populations in Europe and the Caucasus. Here, we are using several techniques such as GC-EAG (Gas chromatography – Electroantennography) to identify the pheromone compounds that elicit male antenna responses, and GC (Gas chromatography) to quantify the amount of compounds in pheromone gland extracts. We are also conducting behavioral assays on small (olfactometer), medium (semi-natural condition) and large (open field) scales to test both female attractiveness and male choice.