Identifying the genetic bases of plant traits and community composition in Populus tremuloides

Community genetics aims to understand the effects of intraspecific genetic variation on community composition and diversity, thereby connecting community ecology with evolutionary biology. Thus far, research has shown that communities associated with a host plant are an extended phenotype of the plant in that the plant genetics underpin the composition of the community (e.g., insects, lichen, endophytes). This work has, however, been conducted primarily at the plant genotype level and has not identified the key underlying genes. To address this gap, we used genome-wide association mapping (GWAS) with a population of 445 aspen (Populus tremuloides) genets to identify the genes governing plant traits (defense chemistry, bud phenology, leaf morphology, growth) and insect community composition. We found 49 significant SNP associations in 13 Populus genes that were correlated with chemical defense compounds and insect community traits. Most notably, we identified an early-nodulin like protein (ENODL) that was associated with insect community diversity and the abundance of interacting foundation species (ants and aphids). In addition, our findings support the concept that particular plant traits are the mechanistic link between plant genes and the structuring of associated insect communities. These findings advance community genetics research, which should further investigate how the effects of these plant genes on associated communities may change with plant ontogeny and environmental context.