title: Positive and purifying selection on the Drosophila Y chromosome.
abstract: Y chromosomes, with their reduced effective population size, lack of recombination, and male-limited transmission, present a unique collection of constraints for the operation of natural selection. Male-limited transmission may greatly increase the efficacy of selection for male-beneficial mutations, but the reduced effective size also inflates the role of random genetic drift. Together, these defining features of the Y chromosome are expected to influence rates and patterns of molecular evolution on the Y as compared with X-linked or autosomal loci. Here, we use sequence data from 11 genes in 9 Drosophila species to gain insight into the efficacy of natural selection on the Drosophila Y relative to the rest of the genome. Drosophila is an ideal system for assessing the consequences of Y-linkage for molecular evolution in part because the gene content of Drosophila Y chromosomes is highly dynamic, with orthologous genes being Y-linked in some species whereas autosomal in others. Our results confirm the expectation that the efficacy of natural selection at weakly selected sites is reduced on the Y chromosome. In contrast, purifying selection on the Y chromosome for strongly deleterious mutations does not appear to be compromised. Finally, we find evidence of recurrent positive selection for 4 of the 11 genes studied here. Our results thus highlight the variable nature of the mode and impact of natural selection on the Drosophila Y chromosome.
authors: Department of Biological Sciences, North Carolina State University ndsingh@nscu.edu.
authors: Nadia D
authors: ND
authors: Singh
authors: Departamento de Genética, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Leonardo B
authors: LB
authors: Koerich
authors: Departamento de Genética, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Antonio Bernardo
authors: AB
authors: Carvalho
authors: Department of Molecular Biology and Genetics, Cornell University.
authors: Andrew G
authors: AG
authors: Clark
mesh_terms: D000818:Animals; D004330:Drosophila / Q000145:classification* / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D008297:Male; D008957:Models, Genetic; D059645:Mutation Rate; D010802:Phylogeny; D012641:Selection, Genetic; D017384:Sequence Deletion; D014998:Y Chromosome / Q000235:genetics*
keywords: Drosophila; Y chromosome; positive selection; purifying selection