Uneven selection pressure accelerating divergence of Populus and Salix

Abstract

Genomics: Salicaceae family members under different selection pressures Different selection pressure on duplicate genes explains how willow and poplar diverged from a common progenitor with four copies of their genome. A study by Tongming Yin and colleagues at Nanjing Forestry University in China compared the genomes of these two fast-growing trees to shed light on how they lost ancestral genes to retain only two copies of their genome. They found an uneven selection pressure on different genomic regions and a faster loss of duplicated genes in willow. This could explain why willow evolved more nascent and gave rise to over 300 species, whereas there are only about 29 species of poplar. Differences in gene density in the sex chromosomes are also key to the divergent evolution of these two sister lineages.