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Erisman, BE, Craig MT, Hastings PA.  2009.  A phylogenetic test of the size-advantage model: evolutionary changes in mating behavior influence the loss of sex change in a fish lineage. American Naturalist. 174:E83-E99.   10.1086/603611   AbstractWebsite

The size-advantage model asserts that mating behavior influences the incidence and direction of sex change in animals. Selection for protogyny (female to male sex change) occurs in mating systems in which large males monopolize and pair spawn with females; however, gonochorism (no sex change) is favored when adults spawn in groups and sperm competition is present. Despite widespread empirical and theoretical support for the model, these predictions have not been tested within a phylogenetic context. Here we show that the loss of sex change within a lineage of reef fishes is influenced by evolutionary changes in two traits related to their mating behavior: mating group structure and sperm competition intensity. Phylogenetic reconstructions of the reproductive evolution of groupers (Epinephelidae) indicate that protogyny and paired spawning are the ancestral conditions for the lineage; both gonochorism and group spawning evolved independently at least four times in three different genera. Evolutionary transformations from protogyny to gonochorism (loss of sex change) are associated with equivalent transformations in mating group structure from paired to group spawning, and sperm competition is considerably higher in gonochoric species than in protogynous species. These results provide explicit phylogenetic support for predictions of the size-advantage model, demonstrating that selection for protogynous sex change decreases as mating group size and sperm competition intensity increase.

Erisman, BE, Buckhorn ML, Hastings PA.  2007.  Spawning patterns in the leopard grouper, Mycteroperca rosacea, in comparison with other aggregating groupers. Marine Biology. 151:1849-1861.   10.1007/s00227-007-0623-2   AbstractWebsite

We documented the spawning patterns of the leopard grouper, Mycteroperca rosacea, from April to June 2005 in the central Gulf of California, Mexico to draw comparisons with other aggregate-spawning groupers and provide information useful for management of their fishery. Adults formed spawning aggregations of 150 to > 700 individuals at specific sites, and spawning occurred daily at these sites from late April through early June. Courtship occurred throughout the day, but spawning was restricted to the evening hours. Adults spawned in groups of 6-40 fish, and pair-spawning was not observed. The group-spawning behavior of adults and the gonosomatic indices of mature males (maximum = 7.2%) suggest that sperm competition was present. The site-specificity of leopard grouper spawning aggregations and diel spawning period were typical of most aggregating groupers, and the size and structure of these aggregations was similar to other species in the genus Mycteroperca. Leopard grouper behavior patterns were unusual in that spawning aggregations persisted for extended periods, spawning was not synchronized with the lunar cycle, and adults aggregated during non-spawning periods. The extensive duration and site-specificity of spawning aggregations and the propensity of M. rosacea to form aggregations year-round increases the vulnerability of the species to overfishing. Policies that limit harvest from these aggregations are needed to improve the management of leopard grouper fisheries in the Gulf of California.