Detecting signatures of selection in candidate cytochrome p450s and glutathione S-transferases between mountain pine beetle (Dendroctonus ponderosae) populations

For mountain pine beetle (Dendroctonus ponderosae), a native forest pest of lodgepole (Pinus contorta) and ponderosae pine (Pinus ponderosa), successful colonization and persistence in healthy pine hosts is dependent on its ability to coordinate mass attack as well as detoxification of host tree defense compounds. Genes belonging to two families of enzymes, cytochrome P450s (CYPs) and glutathionie S-transferases (GSTs), play an important role in detoxification of defense metabolites. Mountain pine beetle CYP genes are also essential in the biosynthesis of aggregation pheromones required for the coordinated mass attacks. The purpose of this study is to evaluate if any of these genes are under selection in different Canadian mountain pine beetle populations using a Pool-seq approach. This study examines mountain pine beetle CYP and GST genes to determine if they are either under positive selection or under selective constraint and examine how selection varies across a gene locus in the two populations. The result of this study was able to show that these genes are under purifying or neutral selection. For some genes there is however population differences in selection across the gene locus which may suggest potential environmental associations of variants in populations of mountain pine beetle that have spread to higher latitudes and onto naïve host trees. This study provides a framework for further functional investigations of variants of these genes and how these population variants change over time.