The Environmental Effect on the Sexual Selection of Guppies (Poecilia reticulata) Patricia Giglio Department of Biological Sciences, York College of Pennsylvania Project Summary Sexual selection is influenced by both social and ecological mechanisms. Previous research focused on the social mechanisms without involving the ecological ones. My study would focus on the effect that an environment would have on the sexual selection outcome in guppies (Poecilia reticulata). I would alter an aquaria by allowing males to visualize one another or not. By doing so, this could alter female choice, courtship behaviors, and male to male and ultimately the outcome of sexual selection. The structure of the habitat could change the way males and females interact and also affect female choice which is thought to be the main mechanism in the sexual selection of guppies. This study will allow for both social and ecological mechanisms to be considered in helping to better understand the sexual selection behaviors of guppies. Introduction Female choice is an important mechanism in the sexual selection process in guppies (Poecilia reticulata). Larger, more conspicuous males have increased mating success (Houde 1987). Males use two mating tactics when attempting to mate with a female. Males use sigmoid courtship displays to gain the female’s attention by positioning himself in front of the female and vibrating his body in an “S” shape. The second tactic is sneak copulation in which the male thrusts his gonopodium without displaying or receiving a receptive response from the female (Brooks and Caithness 1999). Guppies have been known to alter their mating behaviors depending on social and environmental conditions such as the presence of predators and population density. Variations in the sexual behaviors or interactions between males may alter sexual selection. Objective To examine the influence of habitat structure on the sexual behavior of female and male guppies. The structure of the habitat could affect the ability of females to choose the preferred male and therefore influencing the outcome of sexual selection. Review of Literature Houde (1987) found that female choice played a significant role in sexual selection in guppies. The amount or duration of courtship displays by males did not determine male mating success. These results conflicted with a study by Farr (1980) in which he found that male courting rate was a criterion for female choice. Orient and orient then glide responses by the female guppy to a sigmoid display are both reliable predictors of male mating success (Brooks and Caithness 1999). Male to male competition increases as population density increases in guppies. In the natural setting, population densities vary due to the movement throughout rivers, predators, and food availability (Jirotkul 1999). Jirotkul 1999 Phase 1 All barriers opaque. Record the number of sigmoid displays for each male. Recorded whether or not the female responded to each display. Phase 2 Transparent barriers except for the barrier between predators and males. Record the number of sigmoid displays for each male. Recorded whether or not the female responded to each display. Record the amount of time each male spends paying attention to the other males. (darting towards or swimming along barrier with other male). Phase 3 All barriers transparent. Record the number of sigmoid displays for each male. Record whether or not the female responded to each display. Record the amount of time each male spent paying attention to the other males. (darting towards or swimming along barrier with other male). Research Design Expected Results Literature Cited Brigs, S.E., Godin, J., and Dugatkin, L.A Mate-choice copying under predation risk in the Trinidadian guppy (Poecilia reticulata). Behavioral Ecology. 7: Brooks, R. and Caithness, N Intersexual selection, sneak copulations, and male ornamentation in guppies (Poecilia reticulata). S. Afr. J. Zool. 34:48-5. Available from: Academic Search Premier Herdman, E., Kelly, C., and Godin, J Male mate choice in the guppy: Do mals prefer larger females as mates? Ethology. 110: Available from: Academic Search Premier. Houde, A.E The effects of female choice and male-male competition o the mating success of male guppies. Animal Behaviour. 36: Available from: Academic Search Premier Jirotkul, M Population density influences male-male competition in guppies. AnimalBehaviour. 58: Available from: Academic Search Premier. Kangas, N. and Lindstrom, K Male interactions and female mate choice in the sand goby, Pomatoschistus minutus. Animal Behaviour. 61: Kelly, C.D. and Godin, J Predator risk reduces male-male sexual competition in the Trinidadian guppy (Poecilia reticulata).Behav. Ecol. Sociobiol. 51: Available from: Academic Search Premier. Price, Anna and Rodd, Helen F The effect of social environment on male-male competition in guppies (Poecilia reticulata).Ethology[serial online] 112: Available from: Academic Search Premier. Acknowledgments I’d like to thank Dr. Rehnberg for mentoring this thesis project. 1/05/guppy.html