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An Evaluation of an Experimental Model for Sympatric Speciation

Abstract

Abstract

With slight modifications, an attempt was made to repeat the work of Pimentel, Smith and Soans (1967) whose experimental results suggested that disruptive selection on two partially isolated populations of Musca domestica could result in sympatric speciation. The two strains of flies were selected for preference for two different ovipositional attractants with approximately 90% selection pressure for correct choice.

The experiment was pursued through four generations and a number of factors found which complicate interpretation. Because very few flies selected the ovipositional attractant "correctly" at first, the number of flies being used as parents for each generation were very low, resulting in a high degree of inbreeding, and the possibility of gene drift. Numbers of eggs laid, pupal hatch times and migration rates all showed a great variability between the two strains, with gene drift as a possible cause. In addition, freshly laid eggs were found to act as ovipositional attractants, introducing a further source of error into the breeding system.

These are problems that need to be overcome before this type of experiment can be used as evidence for sympatric speciation.