Male boldness and female parental care predict reproductive success in a bi-parental cichlid, the rainbow krib (Pelvicachromis pulcher)

1. Animal personality differences, i.e. consistent among-individual behavioural differences within populations, are prevalent across the animal kingdom. However, we are just beginning to understand the adaptive significance of the observed behavioural variation. We are particularly in need of empirical studies testing hypotheses of proposed theoretical frameworks aiming to understand the existence animal personality differences. In this study, we investigated a hypothesis derived from a framework suggesting that sexual selection may generate and maintain personality variation. The authors of this framework propose parental care as a mechanism linking animal personality and reproductive fitness. 2. We repeatedly measured individual boldness in male and female rainbow kribs, Pelvicachromis pulcher, a West African cichlid known for territorial cave breeding and shared parental care. We then formed 54 breeding pairs with varying behavioural contrasts in boldness. For pairs that produced offspring (N = 20), we repeatedly recorded parental care behaviour (parental boldness and brood guarding) of both parents over one month. Reproductive success was measured as the likelihood to reproduce, the number of offspring, and offspring size at the end of breeding. 3. In both sexes, we found consistent among-individual differences in boldness before breeding and in parental care behaviours. Bolder males were less likely to reproduce but, when breeding was successful, produced bigger broods compared to less bold males. Female parental boldness positively correlated with the number of offspring produced. However, individual boldness before breeding did not predict parental care behaviour in either sex and we found no effects of the pairs' contrast in pre-breeding boldness on parental care coordination or reproductive success. 4. The outcomes of our study may suggest that among-individual variation in male boldness is maintained by males with different behavioural types playing different reproductive strategies of equal average fitness. Future research should delve into understanding the intricate link between male boldness and reproductive success, exploring for instance underlying genetic mechanisms and interactions with environmental conditions.