In this paper, we review the available data on four species exhibiting different types of intra-sexual plasticity in reproduction that have been studied in our lab. Furthermore, the differences between morphs within a given species may involve a set of different traits, including reproductive behavior, the differentiation of male morphological traits, and the patterns of gonad tissue allocation and the differentiation of gonadal accessory glands. These alternative reproductive tactics can be classified according to their plasticity during the life span of the individuals (i.e., fixed vs. One such form of variation consists in the occurrence of alternative male types: males that invest resources in mate attraction and males that exploit the investment of the former males, by trying to sneak fertilizations during spawning. The occurrence of intra-sexual variation in reproduction is a widespread phenomenon in teleosts. These transitions in parental care characters are the most numerous reported for any family of vertebrates and, to our knowledge, provide the first quantitative support for models of parental care evolution in fish. There is also evidence that male-only care evolved once from biparental care. The data support hypothesized transitions in the sex of care-giver, with uniparental female care having arisen from biparental care 21 to 30 times with 0 to 10 reversals. Mouthbrooding has evolved from ancestral substrate guarding with 10 to 14 transitions and 0 to 3 reversals. Here, we assemble the first family-wide composite phylogeny based on morphological and molecular studies, and trace two sets of character evolution: form of care (substrate guarding and mouthbrooding), and sex of care-giver (biparental, female-only, and male-only). These freshwater teleost fish provide parental care for their offspring, display many different forms of care and have interspecific variation in which sex stays with the young. Our results support the hypothesis that biparental mouth-brooding was the ancestral state of both male and female uniparental mouth-brooding in cichlid fishes.Ĭichlid fishes (Cichlidae) are well suited for testing theories of the evolution of vertebrate parental care. The experiments and model together suggest that interspecific variation in remating opportunities and clutch size may be responsible for differences in care patterns within the sub-family Tilapiini. Our experimental results confirm that in St Peter's fish the probability of caring is determined facultatively according to current conditions at each spawn. We attribute this to the associated difference in the fitness benefit of biparental care relative to female-only care. Breeding trials with males of different sizes show that small fathers desert more frequently than large fathers. Manipulations of the operational sex ratio show that males and females desert their offspring more frequently when the costs of care are high (in terms of lost mating opportunities). We first review a game-theoretic model of parental care evolution, predictions of which we test experimentally in this paper. We exploit this unusual variability to isolate conditions favouring biparental versus uniparental mouth-brooding by males or females. In Galilee St Peter's fish, Sarotherodon galilaeus (Cichlidae), male care, female care and biparental care all occur in the same population. Evolutionary theory predicts that differences in parental care patterns among species arose from interspecific differences in the costs and benefits of care for each sex.
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