Phylogenetic basis for understanding genome size evolution in Drosophila

Genome size is a unique character, peculiar to each organism, as it spans the intersection of phenotypic and genotypic value.  As more data is being accumulated for genome size, extreme variation has been found across organisms as much as 7,000 fold in animals, yet does not correlate with complexity.  Most of the variation in size can be attributed to variable levels of noncoding DNA and not gene number; however, how this change occurs throughout evolutionary time is widely debated.  Many hypotheses have been proposed for how genome size changes (low effective population size, mutational equilibrium, and adaptive hypotheses), yet the change has been largely ignored from a phylogenetic standpoint.  Therefore, we utilize phylogenetic comparative methods to uncover the best fitting hypothesis for genome size change in Drosophila species, given the wealth of sequence data and ease of genome size estimation for this group.  We then compare the quantitative DNA differences consequent to the formation of heteromorphic sex chromosomes, in an effort to understand how sex influences genome size evolution, specifically through the chromosomal degradation.  Phylogenetic comparative methods provide a novel and useful way to understanding trait change, and development of these methods with Drosophila will allow us to apply the technique to a variety of other organisms.