Directional selection on morphology In the pheasant, Phasianus colchicus

Abstract:
Directional selection was relatively frequent, and in some instances intense, during a three-year study of a pheasant population. The pheasant is a polygynous species. In addition to weight, tarsus length and wing length, which were studied in both sexes, three beak characters were measured in females, and tail and spur length in males. Both univariate and multivariate techniques were used to estimate selection. Selection associated with survival and reproductive success was detected in both sexes. Selection gradients indicated consistent opposing selection for low weight and long tarsus in association with female survival, while female reproductive success was negatively related to bill length. In males, several phenotypically correlated characters covaried positively with reproductive success, which was measured both as the number of acquired females and the estimated number of sired chicks. However, only the selection gradients for spur length were significant, indicating that spur length is the most important factor for male reproductive success. Male survival was also associated with spur length. This suggests that spur length at the phenotypic level is enhanced by both natural and sexual selection.