Mating Preference in Poecilia Reticulata When in the Presence of Shelter

Mating preference in Poecilia reticulata when in the presence of shelter

Tammy Nguyen

298

Abstract:

        There are many factors that can be held accountable for the success of mating in guppies (P. reticulata). Since males have a higher potential for reproduction, this may cause them to be sexually aggressive when it comes to females. This aggression in turn, causes unresponsive females to seek refuge from the harassment. In this study, we examined the effect that shelter had on the success of mating and interaction in guppies (P. reticulata) by observing guppies’ mating habits in a tank with shelter present and a tank without shelter present. We conducted 15 trials that were 10 minutes each, in which we recorded the amount of time the guppies (P. reticulata) spent closely interacting with each other. We predicted that the presence of a shelter would have a significant effect on the guppies’ (P. reticulata) success rate in mating. However, our results indicate that the presence of a shelter does not have a significant effect on success.

Introduction:

        Organisms have long displayed a number of various techniques and mechanisms when choosing a mate. In 1871, Darwin introduced the theory of sexual selection as intersex competition for members of the opposing sex and the differential choice of said opposing members between competitors (Trivers, R., 1972). More often than not, it is the females that choose between competing males (Aspbury and Gabor, 2015). Females are often noted as the choosier sex due to the females’ higher investments both reproductively and parentally and the operational sex ratio (Aspbury and Gabor, 2015). Females are limited to the number of reproductive eggs in their basket; meanwhile males produce sperm by the gallons. Bokides and Lou and Hamilton noted (2012) that these odds left males with a higher potential for reproduction and could result in a likelier chance of sexual conflict, in this case, coercive mating.

Due to their promiscuous mating systems, guppies (Poecilia reticulata) are a prime species example where sexual coercion is evident (Magurran and Seghers, 1994a). Guppy males (P. reticulata) can achieve mating in two ways. They may either display themselves with the hopes of persuading a receptive female to mate with them, or they may choose sneaky mating (sexual coercion) in which they forcefully thrust their gonopodium towards the female’s genital pore without her consent (Magurran and Seghers, 1994a). Sexual coercion is costly for female guppies’ (P. reticulata), particularly reducing the females’ abilities in sexual selection (Head and Brooks, 2005). The male guppies’ (P. reticulata) sneaky mating attempts are prevalent when females are unresponsive, distracted, or in the presence of other male competitors, and since male guppies (P. reticulata) spend so much of their time attempting to inseminate, it is estimated that female guppies (P. reticulata) are subjected to a sexual coercive attempt every minute (Magurran and Seghers, 1994b). In result, unreceptive female guppies (P. reticulata) are driven into habitats that they otherwise do not prefer to occupy (Darden and Croft, 2008).

In this experiment, we are using guppies (P. reticulata) as our subjects and comparing the effects of the presence versus absence of a shelter in a captive-tank setting in relation to the success of mating rates between female and male guppies (P. reticulata). We predicted that shelter presence would affect the success rates of mating between guppies (P. reticulata), specifically the time the guppies spend closely interacting. If there is a shelter present in the tank then, the average time of interaction between guppies (P. reticulata) will be significantly lower. If there is no shelter present in the tank then, the average time of interaction between (P. reticulata) will be significantly higher.

Methods:

        To test the hypothesis that the presence/absence of a shelter affects the success rate of mating between guppies (P. reticulata), we designed 2 different environments in 2 separate tanks for the guppies (P. reticulata) to interact in. We designed one tank to have 6 different plants for the guppies to use as shelter, and we left the other tank baron. We then placed 2 different sets of guppies (P. reticulata), one male and one female, in each of the tanks and recorded the amount of time the guppies (P. reticulata) spent closely interacting within a body lengths away from each other. In order to avoid stressing out the guppies (P. reticulata), we swapped out the 2 sets of guppies (P. reticulata) every 2 trials.

        After we observed and conducted 15 trials that were 10 minutes long each, we averaged the time the guppies (P. reticulata) spent closely interacting with one another in each environment. We then compared the two averages using a Parametric Parent-T test or Mann-Whitney test in JMP.

Results:

        There was no significant difference in the average amount of time guppies (P. reticulata) spent closely interacting when in the presence of shelter versus no shelter (Mann Whitney test: Z = -1.62, p = 0.11, df = 15, Fig. 1).

Discussion:

        In this study, we examined the effects of shelter on the success rates in mating of guppies (P. reticulata). We suggested that the presence of a shelter would significantly decrease the average success rate of mating between guppies (P. reticulata), specifically interactions. Our results indicated that shelter had no significant effect on the average time that the guppies (P. reticulata) spent closely interacting with one another; therefore our results did not support our predictions, and we accepted the null hypothesis. Although the results showed that there was a slight difference in the average amount of time the guppies (P. reticulata) spent closely interacting with one another, the difference was not significant enough and the results stayed within the standard error margin (Fig. 1).