An Experimental Test of Condition-Dependent Male and Female Mate Choice in Zebra Finches

Marie-Jeanne Holveck,Katharina Riebel,Nicole Geberzahn,Zhanjiang Liu

doi:10.1371/journal.pone.0023974

Abstract

In mating systems with social monogamy and obligatory bi-parental care, such as found in many songbird species, male and female fitness depends on the combined parental investment. Hence, both sexes should gain from choosing mates in high rather than low condition. However, theory also predicts that an individual's phenotypic quality can constrain choice, if low condition individuals cannot afford prolonged search efforts and/or face higher risk of rejection. In systems with mutual mate choice, the interaction between male and female condition should thus be a better predictor of choice than either factor in isolation. To address this prediction experimentally, we manipulated male and female condition and subsequently tested male and female mating preferences in zebra finches Taeniopygia guttata, a songbird species with mutual mate choice and obligatory bi-parental care. We experimentally altered phenotypic quality by manipulating the brood size in which the birds were reared. Patterns of association for high- or low-condition individuals of the opposite sex differed for male and female focal birds when tested in an 8-way choice arena. Females showed repeatable condition-assortative preferences for males matching their own rearing background. Male preferences were also repeatable, but not predicted by their own or females' rearing background. In combination with a brief review of the literature on condition-dependent mate choice in the zebra finch we discuss whether the observed sex differences and between-studies differences arise because males and females differ in context sensitivity (e.g. male-male competition suppressing male mating preferences), sampling strategies or susceptibility to rearing conditions (e.g. sex-specific effect on physiology). While a picture emerges that juvenile and current state indeed affect preferences, the development and context-dependency of mutual state-dependent mate choice warrants further study.

Highlights

Given enough variance in quality of mates, mate choice should increase fitness over random mating both in males and females [1,2,3]
If the costs of targeting the best mates are sufficiently high, low-quality individuals might minimize the costs of choice and lost breeding opportunities by changing the direction of their preferences towards low-quality individuals [9,11]. We recently reported such a quality-assortative preference in female zebra finches Taeniopygia guttata [14] that were allowed to choose between the songs of males in different condition
Experiment 1: Testing female mating preferences Focal females spent on average 6:43600:52

Summary

Introduction

Given enough variance in quality of mates, mate choice should increase fitness over random mating both in males and females [1,2,3]. The net balance of benefits and costs of choice such as time and energy loss from search and competition is expected to differ for individuals in high and low condition [4]. Optimality models of state-dependent mate choice predict reduced sampling effort or choosiness in low-quality individuals if they a) cannot physically afford the costs of prolonged mate search, and/or b) are less successful in competing with their own sex, and/or c) are less successful in attracting the opposite sex, or d) are more likely to be deserted by their mate [1,9,10,11,12,13]. If the costs of targeting the best mates are sufficiently high (e.g. when such mates are rare), low-quality individuals might minimize the costs of choice and lost breeding opportunities by changing the direction of their preferences towards low-quality individuals [9,11]

Methods

Results

Conclusion