When sexual signallers are choosers too

Sexual selection is a potent evolutionary force and was proposed by Darwin because natural selection alone could not explain the evolution of exaggerated sexual signals, like colourful ornaments in birds. Sexual signals for mate choice are commonly investigated with the assumption that one sex is the signaller while the other sex chooses. However, both sexes can be signallers and choosers. When sexual signallers are choosers too, mutual mate choice arises and increases the number and interactions of selection pressures. Mutual mate choice may thus alter the resulting selection pressures on sexual signals. Therefore, it is important to understand the role of both sexes in sexual communication.

While females of the tobacco budworm Chloridea (formerly Heliothis) virescens (Lepidoptera: Noctuidae) attract males via a long-range sex pheromone, males also emit a pheromone from elaborate structures, called hairpencils, at close range. Females use the male hairpencil pheromone for species recognition but whether these chemicals are used by the female to discriminately assess males of different quality was unclear. This thesis researched mutual mate choice by providing evidence for female mate choice in a noctuid moth and determined the male signal underlying female mate choice.

In conclusion, mutual mate choice in C. virescens exists, but this mutual choice is based on different types of signals: while females attract males via a sex pheromone, males signal their attractiveness not through the biosynthetically related male hairpencil pheromone, but through another signal that conveys information about male size.

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