Male ornamentation and constitution during mate choice in the guppy, Poecilia reticulata

This study evaluated the mating behavior of the guppy, Poecilia reticulata, in the framework of the Fisherian and adaptive models of female choice. The first experiment evaluated the relationship between swimming performance and caudal fin shape, dorsal fin length, and the intensity of the carotenoid pigments. There was no relationship between swimming performance and caudal fin shape or dorsal fin length. However, there was a positive relationship between swimming performance and carotenoid pigments, indicating that carotenoid pigments are condition-dependent traits.;The second experiment evaluated the relationships between male constitution, ornamentation, sexual behavior, and attractiveness to females. Male ornamentation was quantified as the area and number of orange, black, and structural color spots and by calculating the complexity of a male's color pattern. Swimming performance and a calculated condition factor were used to estimate constitution. Male display rate and attractiveness were also determined. Male ornamentation and displays are condition-dependent in guppies. Displays, ornament complexity, and area of orange were correlated with sustained swimming performance, and to a lesser extent, with the condition factor. Males that females responded to had higher display rates, more complex ornamentation with more carotenoid pigments, and higher swimming performance than males that females did not respond to.;The third experiment consisted of a breeding experiment. This experiment tested for differences in the constitution of offspring from females mated with preferred males and offspring from females mated with non-preferred males. There were no significant differences between offspring that were attributable to sire type. However, there were significant dam-family and sire-type dam-family interactions in all three analyses, indicating potential genetic effects. Broad and biased narrow sense heritability estimates showed that heritable variation probably exists for prolonged swimming performance, physical condition, and display rate. The results of this and studies on other fish have shown that these measures of constitution are correlated with components of viability. This study indicates that current day female choice may be adaptive. This suggests that these ornaments evolved by adaptive female choice, however, these results are also consistent with predictions that can be made at either the beginning or ending of the Fisherian process.