Growth and male ornamentation in Xiphophorus montezumae

Juvenile growth rate is an important life-history trait that affects the size at maturity, and may influence the development of sexual ornamentation. The sword of several species of the genus Xiphophorus (Teleostei: Poeciliidae) is an elaborate secondary sexual trait that confers an advantage in terms of sexual selection, counterbalanced by locomotive and predatory costs. This study assesses differences in male juvenile growth, age, and size at maturation and their relationship with maximum body size and sword elongation in Montezuma swordtails (Xiphophorus montezumae). Fish size and sword length were measured over the course of 20 months. The size at which individual males initiated sword elongation varied considerably among individuals. Male maximum body size was correlated with early growth rate and age of maturation, and sword growth rate was positively correlated with male size at the onset of sword growth. Early growth in X. montezumae may provide valuable information about performance in subsequent stages and about probable future reproductive success. © 2011 Taylor & Francis.