title: Small and poor females change sex: a theoretical and empirical study on protogynous sex change in a triggerfish under varying resource abundance.
abstract: Sex change is known from various fish species. In many polygynous species, the largest female usually changes sex to male when the dominant male disappeared, as predicted by the classical size-advantage model. However, in some fishes, the disappearance of male often induces sex change by a smaller female, instead of the largest one. The halfmoon triggerfish Sufflamen chrysopterum is one of such species. We conducted both field investigation and theoretical analysis to test the hypothesis that variation in female fecundity causes the sex change by less-fertile females, even if they are not the largest. We estimated the effect of body length and residual body width (an indicator of nutrition status) on clutch size based on field data. Sex-specific growth rates were also estimated from our investigation and a previous study. We incorporated these estimated value into an evolutionarily stable strategy model for status-dependent size at sex change. As a result, we predict that rich females change sex at a larger size than poor ones, since a rich fish can achieve high reproductive success as a female. In some situations, richer females no longer change sex (i.e. lifelong females), and poorer fish changes sex just after maturation (i.e. primary males). We also analyzed the effect of size-specific growth and mortality.
authors.affiliation: Department of Information and Computer Sciences, Nara Women's University, Kitauoyanishi-machi, Nara 630-8506 Japan. syamaguchi@bio-math10.biology.kyushu-u.ac.jp
authors.forename: Sachi
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Satoko
authors.initials: S
authors.lastname: Seki
authors.forename: Kota
authors.initials: K
authors.lastname: Sawada
authors.forename: Satoshi
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D005260:Female; D005298:Fertility / Q000502:physiology; D005399:Fishes / Q000033:anatomy & histology* / Q000254:growth & development / Q000502:physiology*; D057850:Hermaphroditic Organisms / Q000254:growth & development / Q000502:physiology*; D008297:Male; D008954:Models, Biological