MIG Seminar Series - Hiroshi Akashi - Population genomics of weak evolutionary forces: Base composition evolution in Drosophila

Seminar/Forum

MIG Seminar Series - Hiroshi Akashi - Population genomics of weak evolutionary forces: Base composition evolution in Drosophila

Population genomics of weak evolutionary forces: Base composition evolution in Drosophila

Weak evolutionary forces may be prevalent in genome evolution, but are, by definition, difficult to measure directly. Population genetic inference can be a powerful approach to distinguish between mutation/drift and fixation biases including natural selection and biased gene conversion. Knowledge of ancestral and derived states in DNA can greatly enhance such approaches, but even small methodological biases can mimic the effect of the evolutionary forces of interest. We have developed methods for ancestral state inference that can account for lineage-specific and strongly biased base composition and that can be employed for within-species data for recombining regions (where gene trees may differ among sites). Analyses of simulated data support the accuracy and robustness of the approach. We are applying these methods for large-scale analyses of polymorphism and divergence in Drosophila melanogaster and close relatives. We focus on base composition evolution and have found evidence for strong heterogeneity and lineage-specificity in fixation biases within and among synonymous mutations and intron changes. Neutrally evolving sites are valuable as a "control" in such analyses but appear to be rare in Drosophila genomes.

Presenter

  • Professor Hiroshi Akashi
    Professor Hiroshi Akashi, Professor of Evolutionary Genetics