US-Belgium Cooperative Research: Protandrous Fishes as Tests of Sex Allocation Theory

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This award will support collaborative research between Dr. Robert Warner, Marine Science Institute, University of California at Santa Barbara and Dr. Francois Wernerus, Staresco Marine Laboratory, Calvia, Corsica. The objective of the project is to study protandrous fishes (those which change sex from male to female) to test theories of sex allocation. Evolutionary ecologists have long been interested in the phenomenon of sex change in fishes. Within this group the patterns of sexuality show extreme variety, and this variety has often been used to explore the adaptive significance of sex allocation. Sex allocation theory deals with the evolutionary dynamics of sexual expression: sex ratio, hermaphroditism and related topics. Ever since this theory began to develop in the mid-seventies, it has been pointed out that there is a critical need to document the mating systems of species that are protandrous. Theory predicts that these species should have mating systems in which mating occurs in random pairs or small groups, such that there is a size advantage in reproduction accrued by small males relative to small females. The investigators propose to test these predictions by assessing size-specific mating success and mating group size in four sparid fishes common in the Mediterranean. Two of these species are protandrous, one changes sex in the opposite direction, and one does not change sex. Comparisons between these species will offer a powerful test of theory. The research will be carried out at the Staresco Marine Laboratory in Corsica, which is a major center for research in marine behavioral ecology. The research will benefit from the theoretical expertise of Dr. Warner and the experimental experience of Dr. Wernerus.