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Former Graduate Student & Specialist: Larry Cabral

Interests: Experimental Evolution; Speciation; Drosophila; Sexual Conflict; Genomics

Background: Since Darwin published the Origin of Species, biologists have had protracted differences about the importance of alternative mechanisms of speciation. Some biologists have contended that ecological selection is a common force in creating reproductive isolation, while others have disagreed. Thus the role that selectively-established differentiation of populations plays in first creating reproductive isolation is still debated. By using replicate outbred populations of Drosophila melanogaster that have been experimentally evolved under contrasting as well as parallel selection regimes, it is possible to test the relative importance of ecological selection versus other evolutionary forces in initiating reproductive isolation.

Research Objectives: The primary research objective is to quantify the relative importance of ecological selection versus other evolutionary mechanisms in any reproductive incompatibility detected in this laboratory radiation of populations. A general experimental design model has been developed that leads directly to methods for achieving such quantification.

Methods and Analysis: Multiple populations of D. melanogaster divided among distinct selection regimes, each regime replicated five-fold at the population level, will be crossed to measure the fitness of the resulting hybrids relative to parental populations. The hybrid assays will measure both prezygotic (survival & mate choice) and postzygotic (hybrid fecundity & viability) incompatibility. Reproductive compatibility will then be statistically partitioned into components due to generation number alone versus composite indices of phenotypic divergence.

Intellectual Merits: A research system in which replicated outbred treatments have been adapting in parallel for hundreds of generations is rare. This research project provides an opportunity to quantify the relative importance of two general mechanisms of speciation which have been contending alternatives for more than a century.

Broader Impacts: This research will provide another illustration of the value of long-term experimental evolution as a powerful tool for the resolution of major issues in biology. In addition, agricultural R&D has long depended on the development of novel breeds, strains, and varieties. Experimental evolution is at the vanguard of developing our understanding of the potential for selection and other evolutionary processes to produce differences between agricultural stocks of animals and plants, and the proposed research will reveal how readily such agricultural breeds can be crossed in future, particularly among animal stocks.

This work is supported by the National Science Foundation- Award No. DEB-1311644


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