Frequency-Dependent Mate Selection in the Guppy (Poeciliidae: Poecilia reticulata)

Abstract

Heterogeneity within a population enhances its long-term survival. A fundamental method of maintaining population heterogeneity is the retention of rare or uncommon phenotypes by selective mating strategies. Employing two color morphs, red tuxedo and red, of the guppy (Poecilia reticulata, Poeciliidae), this study was designed to investigate whether P. reticulata females would preferentially seek out heterogeneous groupings of males exhibiting two color morphs. Adult female guppies were exposed simultaneously to two groups of males (n=10); one comprised of only the tuxedo color morph (n=5) and the other of both color morphs (n=5). For the latter group, the ratio of males exhibiting the two colorations was changed incrementally over multiple trials, beginning and ending with homogeneous groupings (5:0, 4:1, 3:2, 2:3, 1:4, 0:5). Experiments were conducted employing a 76 L aquarium partitioned at both ends to house the male groups. Individual females were placed into an acclimation, holding column located in the center compartment of the experimental aquarium. Subsequent to a five minute acclimation period in the holding column, each female was released. Courting behaviors and population affinities (i.e. female location relative to the male compartments) were recorded every five seconds over a five minute observation period. Females did not show a preference for male groupings exhibiting either the 4:1 or 1:4 color ratios. However, females clearly showed affinity for the male groupings of 3:2 and 2:3 (p <0.05). This investigation on female mate choice in P. reticulata clearly reveals that a mating strategy is occurring in this species and that it is frequency-dependent.