Rapid polygenic adaptation in a wild population of ash trees under a novel fungal epidemic.

Rapid evolution through small shifts in allele frequencies at thousands of loci is a long-standing neo-Darwinian prediction but is hard to characterize in the wild. European ash tree ( ) populations have recently come under strong selection by the invasive fungal pathogen . Using genomic prediction models based on field trial phenotypes and 7985 loci, we show a shift in genomically estimated breeding values in an ancient woodland, between adult trees established before the epidemic started and juvenile trees established since. Using simulations, we estimate that natural selection has eliminated 31% of the juvenile population. Thus, we document a highly polygenic heritable microevolutionary adaptive change over a single generation in the wild. Polygenic adaptation, in which selection acts on many variants at once, may serve an important role in adaptation, but it is harder to detect than selection acting on few loci of large effect. Metheringham . looked at genomic changes in the European ash, , the numbers of which have been decimated in recent decades by a fungal pathogen, . They found that a previously generated list of about 8000 potential variants showed significant differences in allele frequencies between juvenile and adult trees, and these differences were larger than randomly selected variants. This result suggests that polygenic adaptation may indeed be occurring in this population and that some of these variants may point to intervention targets. —Corinne Simonti

Project(s)

Priority 2: Trait Diversity and Function

Priority 1: Ecosystem Stewardship

Funder

Funder name	Awards
Department for Environment Food and Rural Affairs, United Kingdom	Future Proofing Plant Health Programme - Centre for Forest Protection
Department of Agriculture, Food and the Marine, Ireland	Teagasc Walsh Fellowship
Natural Environment Research Council, United Kingdom	London DTP PhD studentship
UK Research and Innovation, United Kingdom	Future Leaders Fellowship (MR/T019832/1)