Mate Selection by Male Winter Moths Operophtera Brumata (Lepidoptera, Geometrldae): Adaptive Male Choice or Female Control?

Abstract

Abstract Mate choice is an important component of sexual selection. It is expected to evolve if the benefits of choice outweigh the costs. Yet, the relative importance of costs and benefits in the evolution of mate choice remain poorly understood. In this study we present experimental evidence for adaptive mate choice by males, but not females, in the winter moth. In a series of experiments we show that: (a) males have a higher probability of attempting to copulate, and consequently also a higher probability to copulate with a larger, more fecund female; (b) if males are given the choice between two females they are more likely to copulate with the larger female; and (c) females do not seem to show any mate discrimination. A sample of winter moths collected in copula in the field did not show any assortative mating for body size. This is the first demonstration of male choice in a moth species with chemical communication. This choice is possibly based on variation in female pheromone quality and/or quantity. We argue that the relatively higher variation in female quality and the limited number of male matings probably have led to male choosiness despite a strongly male biased operational sex ratio. This is consistent with recent studies indicating that choice and competition may occur more frequently in the same sex than previously thought.