MATE SELECTION BY MALE WINTER MOTHS OPEROPHTERA-BRUMATA (LEPIDOPTERA,GEOMETRIDAE) - ADAPTIVE MALE CHOICE OR FEMALE CONTROL

Mate choice is an important component of sexual selection. It is expec ted to evolve if the benefits of choice outweigh the costs. Yet, the r elative importance of costs and benefits in the evolution of mate choi ce remain poorly understood. In this study we present experimental evi dence for adaptive mate choice by males, but not females, in the winte r moth. In a series of experiments we show that: (a) males have a high er probability of attempting to copulate, and consequently also a high er probability to copulate with a larger, more fecund female; (b) if m ales 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 a ny mate discrimination. A sample of winter moths collected in copula i n the field did not show any assortative mating for body size. This is the first demonstration of male choice in a moth species with chemica l 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 pr obably have led to male choosiness despite a strongly male biased oper ational sex ratio. This is consistent with recent studies indicating t hat choice and competition may occur more frequently in the same sex t han previously thought.