Does sexual selection favour consistent behavioural differences in biparental cichlids?

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Behavioural flexibility should be an advantage in a world where environmental conditions change. Yet, there is increasing evidence for the existence of consistent behavioural differences among individuals of the same population across the animal kingdom. Functional explanations for the existence of such puzzling personality differences have recently been proposed, but as yet, little consideration has been given to test hypotheses empirically. Here, we aim to test one of these hypotheses: we propose to investigate the role of sexual selection in generating and maintaining the two aspects of animal personality, among-individual variation in the mean level of behaviour and variation in intra-individual behavioural consistency. We will test predictions for the existence of both types of variation based on a recent sexual selection framework (Schuett et al. 2010). We will focus specifically on novel applications of the framework; that compatibility in personality traits within pairs improves cooperation, coordination and predictability in offspring care and subsequent reproductive success and that therefore individuals choose their partner on the basis of personality traits (behavioural level and degree of consistency), and potentially also consider their own personality in the process. To tackle our questions we will conduct a combination of breeding and mate choice experiments using the biparental rainbow krib, Pelvicachromis pulcher, as model system. We will assess parental care coordination in pairs consisting of different personality combinations (both in terms of behavioural level and consistency), including underlying hormonal mechanisms, and subsequent reproductive success. Furthermore, we will examine whether reproductive consequences of personality combinations are reflected in female and male mate choice patterns: we will first correlatively and then experimentally test which aspect of personality (behavioural level or consistency; in aggression and risk-taking) plays a role during mate choice and whether individuals consider their own personality in their choice. By experimentally manipulating both the behavioural level and the degree of consistency of the chosen sex, we will be able to disentangle the relative importance of each personality component during mate choice for the first time. The proposed project will give novel insights into the existence of animal personality and the resolution of sexual conflict over parental investment. Given that within-species variation is the raw material for selection, studying the function and mechanistic underpinning of consistent behavioural variation within a species (personality variation) is furthermore important for understanding selection and the existence of behavioural diversity. Therefore, this study will have general implications for numerous fields in biology, ranging from behavioural and evolutionary ecology to conservation biology.