Competition is known to play a major role in the establishment and structure of plant communities, with many plants exhibiting allelopathy to mitigate these effects. Solidago canadensis, a native, perennial herb of open habitats in eastern North America, is known to exhibit allelopathic properties. Solidago canadensis requires pollination from insects and also supports a diverse suite of herbivores, which may also respond to plant chemistry. To relate chemical diversity/composition to ecological function, we grew 24 different clones of Solidago canadensis, within single-clone plots. Chemical composition of each clone was quantified via HPLC. For each clone, foliar insects were assessed three times throughout the growing season with sticky cards and three pollinator surveys were conducted. We measured biomass and stem density as measures of plant performance for each clone, as well as the biomass of non-Solidago species within each plot as a measure of competitive ability. NMDS ordinations were conducted on plant chemistry, foliar insects, and floral visitors. Pearson correlations were then conducted to assess relationships between chemical composition, plant performance, floral visitation, and/or foliar insect communities.
Results/Conclusions
Plant chemical composition varied dramatically across the 24 Solidago canadensis clones, represented by three NMDS ordination axes. Plant performance measured by increasing stem density and decreasing light penetration were both associated with chemical NMDS axis 3. However, the biomass of associated species did not vary with plant chemistry. The foliar insect community varied little across clones and was independent of plant chemical composition, with no associations with the chemical NMDS. In contrast, floral visitors did vary across clones and were associated with chemical NMDS axis 1. Floral visitors were also associated with the plant performance variables of above ground biomass, flower mass, and light penetration. Though foliar insects appeared to be independent of plant chemistry, plant performance and floral visitors were associated with different aspects of plant chemical composition. This suggests multiple ecological functions of plant chemistry that vary across S. canadensis clones, altering their performance and associated insects. Future work will include direct competitive trials to explicitly link plant chemical composition to plant-plant interactions.