Similar rates of protein adaptation in Drosophila miranda and D. melanogaster, two species with different current effective population sizes

摘要: Adaptive protein evolution is common in several Drosophila species investigated. Some studies point to very weak selection operating on amino-acid mutations, with average intensities the order of Nes ~ 5 D. melanogaster and simulans. Species lower effective population sizes should undergo less adaptation since they generate fewer mutations ineffective a greater proportion beneficial mutations. Here I study patterns polymorphism divergence at 91 X-linked loci miranda, roughly 5-fold smaller size than melanogaster. Surprisingly, find similar fraction being driven fixation by positive miranda Genes higher rates show levels neutral diversity, pattern predicted recurrent adaptive evolution. fit hitchhiking model estimate an magnitude coefficients for miranda. This analysis suggests that may not be major determinant adaptation. Instead, mutation-limited, or distribution fitness effects might differ vastly between different populations. Alternative explanation such as biases estimating slightly deleterious mutation models are also discussed.