Population Growth And Fitness In Drosophila

Author : Julia B. Saltz
Publisher :
ISBN 13 : 9781267240767
Total Pages : pages
Book Rating : 4.2/5 (47 download)

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Download or read book Social Gene-environment Correlation written by Julia B. Saltz and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: What makes individuals unique? Both humans and animals show consistent individual differences in behavior that persist across time and across situations. Such differences between individuals within a population, now documented in large array of species, raise two fundamental questions. 1) Why would individuals from the same species, reared in the same population, be different? And, 2) what forces maintain variation in behavior? I.e., why doesn't the "best" behavioral strategy take over? Individual differences may be due to differences in genetic factors, environmental effects, and the complex interplay between these. One approach to interpreting these factors is to analyze the ways in which an individual's genotype influences his social experience. This process, termed 'social gene-environment correlation' (social rGE), can occur whenever genotypes differ in key behaviors--such as conspecific attraction--that determine social experience. Because the social environment can affect both the development of behavior and selection on behavior, social rGE represents a potentially powerful explanation for the development and evolutionary maintenance of individual differences in social behaviors. For my dissertation, I developed the fruit fly Drosophila melanogaster as a system to study individual differences in social behavior. D. melanogaster is ideal because genetic tools allow many "replicates" of natural genotypes--equivalent to identical twins--to be reared under controlled conditions. This simple technique represents an exceptionally powerful tool to dissect the genetic and social environmental causes of individual differences. Using this approach, I was able to directly examine the behavioral causes and fitness consequences of social rGE. I discovered two mechanisms of social rGE. First, I found that natural male genotypes of D. melanogaster differ in social preference behavior (Chapter 1). Male genotypes differ in the amount of time they prefer to spend aggregating with other flies; and they differ in group-size preferences. Because these social preferences directly affect males' opportunity for social experience, genetic variation in social preferences represents a straightforward mechanism of social rGE. Second, I discovered that more aggressive male genotypes experience smaller group sizes (Chapter 2). This correlation between genetically-influenced behavior and the social environment is the hallmark of social rGE. These studies demonstrate that social rGE is pervasive in D. melanogaster. Social rGE may be rampant; but does it matter? I found two means by which social rGE can influence the outcomes of selection. In Chapter 2, both aggressive and non-aggressive genotypes could achieve high mating success (a key fitness proxy), by "using" social rGE to generate the environment in which they were most adept at mating. The relationship between aggressiveness (the mechanism of social rGE) and mating ability shows a pattern characteristic of disruptive correlational selection, which adaptively maintains genetic variation. In other words, social rGE may allow alternate behavioral strategies to enjoy high fitness. Second, in Chapter 3 I examined how groups with different genotypic compositions influence the survival of D. melanogaster larvae. The genotypic compositions I chose represent different choices that female flies must make before ovipositing; these maternal decisions are critical to the social environment of their offspring. I found that more genetically diverse groups--such as those formed by females who prefer share breeding substrates with unrelated females--exert stronger selection against a lower-quality laboratory genotype. Taken together, these results demonstrate that social rGE can have important evolutionary consequences. My dissertation work shows that social rGE is common and has important impacts on fitness in D. melanogaster. This work has implications for humans, in which social rGE has been widely hypothesized but never directly examined; and for other social animals, in which social rGE is rarely considered.