THE INHERITANCE OF QUANTITATIVE FITNESS TRAITS IN GUPPIES, POECILIA RETICULATA (PISCES: POECILIIDAE).

Abstract

The genetic system underlying fitnessrelated traits affects the maintenance of variation in those traits by selection. O'Donald (1980) showed, for instance, that the mode of inheritance of sexually selected characters, the type of trait to be considered here, can influence both the outcome of selection and the rate at which evolutionary equilibria will be achieved. If selection operates on several traits simultaneously, it is important to know both the limitations imposed by the genetic structure of each trait and the extent to which the characters have a common genetic basis. Here I examine inheritance of quantitative patterns of sexual and aggressive behavior in laboratory strains of guppies (Poecilia reticulata), small live-bearing fishes native to streams and rivers in northeastern South America and adjacent Caribbean islands (Rosen and Bailey, 1963). There is extreme polymorphism in male secondary sexual coloration within and among populations (Regan, 1906, 1913; Haskins et al., 1961; Endler, 1978), and it appears that female preference for males with rare or novel coloration is a factor maintaining polymorphisms within populations (Farr, 197 7, 1980b). The preference for rare or novel males facilitates maintenance of high levels of heterozygosity in a female's offspring and is believed to be an adaptive response for increased homeostatic capabilities of a female's offspring in a temporally variable tropical environment (Farr, 1980b). Male guppies court females continuously, up to 13 times per 5 min in natural