Functional and evolutionary genomic inferences in <i>Populus</i> through genome and population sequencing of American and European aspen

Abstract

Significance We performed de novo, full-genome sequence analysis of two Populus species, North American quaking and Eurasian trembling aspen, that contain striking levels of genetic variation. Our results showed that positive and negative selection broadly affects patterns of genomic variation, but to varying degrees across coding and noncoding regions. The strength of selection and rates of sequence divergence were strongly related to differences in gene expression and coexpression network connectivity. These results highlight the importance of both positive and negative selection in shaping genome-wide levels of genetic variation in an obligately outcrossing, perennial plant. The resources we present establish aspens as a powerful study system enabling future studies for understanding the genomic determinants of adaptive evolution.