Genomic Footprints of Speciation and Selection in Populus Trichocarpa (Western poplar).

Climate change is having an impending effect on the genetics of organisms, especially the

ones that have long life span and a slow rate of reproduction. This effect has already been

seen in trees as the change in range of some species, and change in timings of different

phenological traits. In order to deal with this impact, species need some amount of time to

modify their genetics, and come up with mechanism of survival. Considering the pace of

climate change, and its predicted pace in future (by the IPCC), we can’t leave it up to plants

and need to come up with some strategy to help mitigate these climate effects. One solution

to this problem is by studying the genetics of the organism, i.e. trees in our case, and

identify the genes and patterns of genetic variation, which could play a significant role in

controlling physiology and phenology of the organism. Identifying those gene variants in

the natural population and selecting and deploying the favorable genotypes, which can

perform better in the predicted future weather scenario (termed as assisted migration)

could help us deal with this problem.

In this study, we sequenced 456 accessions of Populus trichocarpa, from all across the west

coast. We used population genomic approaches and evolutionary genomics scenarios to

build different speciation and demographic models, and tried fitting those models with the

empirical data. Using statistical approaches as Maximum Likelihood, and Akaike

Information Criterion (AIC), we selected the best demographic model in our scenario. We

also used various parallel approaches to verify our results, and used FST based methods to

find the significant snps’ associated with diversifying selection or local adaptation.

Using these results helped us define what are the major factors effecting the genetics of the

organism, and which patterns of genetic variation are important for local adaptation.