Title: Comparative population genomics in animals and plants: genetic diversity, selection efficacy and effective population size

Abstract:

What determines levels of genetic diversity within species is a central question in evolutionary biology but has remained a puzzling question for decades. Particularly the relative influences of species biology and ecology versus population history have been much debated. To address this question we investigated the genome-wide diversity of 76 non-model animal species by sequencing the transcriptome of two to ten individuals in each species. The distribution of synonymous genetic diversity (π_S) between species revealed no detectable influence of geographic range or invasive status but was accurately predicted by key species traits related to parental investment: long-lived or low-fecundity species with brooding ability were genetically less diverse than short-lived or highly fecund ones. We extended this analysis to a comparison with plant by analysing full-genome data in 34 animal and 28 plant species. As in animals, we found a strong effect of longevity and, in addition, of mating systems. We also found that the efficacy of purifying selection, as measured by the ratio of non-synonymous vs synonymous diversity (π_N/π_S), strongly and negatively correlates with genetic diversity (π_S), in agreement with the nearly neutral theory where effective population size determines both genetic diversity levels and selection efficacy. In plants, however, the relationship was weaker because of substantial variation in mutation rates among species. Finally, we found that the distribution of fitness effect of mutations also varies among species, contributing to variation in πN /πS. Overall, our results suggest that variation in effective population sizes, mutation rates and selection should be jointly considered to explain patterns of genetic diversity.    

After the seminar there will be gløgg and æbleskiver (mulled vine and baked round cakes of pancake dough for those not familiar with this Danish Christmas dish) in the lunch room!