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The Impact of Predation on Life History Evolution in Trinidadian Guppies: Genetic Basis of Observed Life History Patterns

David Reznick
Evolution
Vol. 36, No. 6 (Nov., 1982), pp. 1236-1250
DOI: 10.2307/2408156
Stable URL: http://www.jstor.org/stable/2408156
Page Count: 15
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The Impact of Predation on Life History Evolution in Trinidadian Guppies: Genetic Basis of Observed Life History Patterns
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Abstract

Genetically based life history differences are described in guppies exposed to differences in predator-mediated age-specific survivorship in their natural environment in Trinidad. At one type of locality, the killifish Rivulus hartii is the only potential guppy predator. Rivulus preys selectively on small, immature size classes of guppies. At a second type of locality, the pike cichlid Crenicichla alta and other predators prey selectively on large, mature size classes of guppies. The second generation of laboratory reared guppies from two Rivulus and two Crenicichla localities are genetically different for most of the variables discussed in a previous study on field collected fish (Reznick and Endler, 1982). Crenicichla guppies have earlier ages and smaller sizes at maturation in males and at first parturition in females. They also have smaller offspring, more offspring in the first litter, shorter interbrood intervals, and greater reproductive efforts (estimated as the percent of consumed calories devoted to reproduction). These trends in life history patterns are in close agreement with predictions made by life history theory. Decreased adult survivorship (i.e., Crenicichla predation) is predicted to favor increased reproductive effort and decreased age at maturity. Decreased juvenile survivorship (i.e., Rivulus predation) should favor the opposite response. These are precisely the trends observed in the study on field collected fish (Reznick and Endler, 1982) and in the genetic study presented here.

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