Measuring female mating preferences

Abstract

Interest in the evolution of female mating preferences has increased greatly in recent years, and numerous hypotheses have been proposed to explain how mating preferences evolve. Despite this interest, little is known about how selection acts on mating preferences in natural populations. One reason for this lack of information may be that experimental designs commonly used for testing female preferences make it difficult to quantify the preferences of individual females. Most commonly used designs share three features: they examine the preferences of populations of females, they test female responses when they are presented simultaneously with two stimuli, and they infer information on female preferences by observing female choices between alternative stimuli. Population-level choice tests, in which each female is tested only once with a set of stimuli, do not evaluate within-female variation in preference, which is necessary to document between-female variation in preference. Two-stimulus designs test only for directional preferences if female responses are tested with only a single pair of stimuli. In addition, dichotomous scoring of female responses makes detection of between-female variation in preference difficult. Simultaneous stimulus presentations can confound female preference and female sampling behaviour. An alternative method to assess female preferences is to measure repeatedly the preference functions of individual females using a single-stimulus design. The shape of a female's preference function indicates how a female's mating response varies with male trait value, and repeated measures of individual preference functions allow measurement of within- and between-female variation in preferences.