Predation and natural selection - guppy example

Shakuntala Makhijani

In the readings and material for the lecture on Wednesday, November 4, the concept of predation as a powerful mechanism for natural selection is discussed. I found and article in Behavioral Ecology and Sociobiology called “Predation risk reduces male-male sexual competition in the Trinidadian guppy (Poecilia reticulata)” that discusses this process. Under conditions without predation, males compete to mate with females through courtship displays, and females are selective of mates and avoid attempts of sneak copulation by males through which the female would not be able to select her mate. Under conditions where predators are present, male guppies engage in less competition for a few possible reasons. One reason is that engaging in courtship displays increases guppy conspicuousness to predators and reduces their vigilance against predators. Female guppies also adjusted their behavior with the presence of predators and because less choosy by responding less to male courtship displays and reducing avoidance of sneak copulation attempts. This behavior by females also reduces the benefit for competition between males. In the long term, reduced male-male competition in the presence of predators could have fitness consequences for the population if success in courtship displays is related to the fitness of male guppies since females might no longer be choosing the most robust male guppies to mate with. This study is also an example of how interaction with predators shape intraspecific interactions.

Kelly, C.I. and J. G. Godin, “Predation risk reduces male-male sexual competition in the Trinidadian guppy (Poecilia reticulata)”, Behavioral Ecology and Sociobiology, Dec 2001, Vol. 51 no. 1 pp. 95-100.

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