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In 1976 two biologists David Reznick of the University of California at Riverside and John Endler of the University of California at Santa Barbara traveled to the West Indies island of Trinidad to begin the first in their inclusive series of studies concerning evolution Their studies focused on the vast population of guppies After over a decade of researching the guppies the two biologists came to the conclusion that the guppies were able to evolve a great amount in a small duration of time This not only supported Darwins theory of evolution but more specifically his idea of natural selection There was also one other theory which was very important that was the life-history theory This theory predicts that reduced adult survival will select for earlier maturation and increased reproductive effort Impact of predation On other hand reduced adolescent survival will select the opposite This theory has only been proven in laboratory studies and cannot assess that of natural populations In the experiment conducted by Mr Reznick and Endler they support the predictions of the life-history theory with guppies Natural populations of guppies Poecilia reticulata along the El Cedro and Aripo rivers are found in simple communities and live in one of two predation areas high or low Evaluation of the rate In the high predation areas the main predator is the Pike Cichlid Crenicichla alta other predators include different types of cichlids and characins The Crenicichla alta mainly prey on the larger more sexually mature guppiesImpact of predation The predators which reside in high predation areas are excluded from parts of the upstream because of rapids and waterfalls The low predation areas are located in the upstream of the rivers In these areas there is only one predator and that is the Killifish Rivulus hartii The Rivulus hartii is an omnivore it therefore does not prey on guppies exclusively but only sometimes When the Rivulus hartii do prey on the guppies they
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