Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Scott J. Meiners


Competition is a major driving force in the abundance, distribution, and diversity within any biological system. Plants are more likely to suffer reductions in fitness as a consequence of competition, as they typically occur in dense communities. Individuals within these populations must respond to both inter- and intraspecific competition. Recent studies suggest that the ability to distinguish kin from non-kin may play an integral role in the success of individuals within different plant populations and communities. However, a less known interaction is that between individual clones within a genet as they grow, spread, and begin to interact with nearby rival genets.

This study focused on the ability of Solidago altissima ramets to differentiate between self and non-self interactions, and the role that these responses have in mitigating competition. Plant samples were obtained from wild populations occurring at the Douglas-Hart Nature Center, Mattoon, Illinois. Rhizomes from five different genets were harvested and grown in no competition (rhizome grown singly), self, and non-self treatments. Rhizomes were cut to 10 cm for standardization and allowed to grow for 18 weeks. Leaves were collected after approximately 6 weeks for leaf area analysis, aboveground biomass was harvested after 15 weeks, and rhizome biomass was harvested after 18 weeks. All harvested samples were placed in an oven and allowed to dry at 60 °C for a minimum of two weeks before mass determination. These data were then used to evaluate competitive responses for each measurement by genotype and competitive interaction (self/non-self).

Controls (no competition) were used to establish a baseline for growth and demonstrated no significant variation inherent to the different genotypes used in the experiment. In contrast, all measurements taken from the competition treatments showed significant variation by genotype. However, the results for aboveground and rhizome biomass were indicative of a general competitive response, as responses to both self and non-self interactions were identical. Leaf area, on the other hand, demonstrated both a significant variation by genotype and by competitive interaction, where-in self treatments produced smaller leaves than non-self treatments.

Changes in leaf structure would be correlated with direct competitive responses both above and below ground. Variation in leaf area between self and non-self treatments is indicative of differing competitive responses; however, many of the mechanisms and consequences for this particular change in responses have yet to be identified. Future work should focus on root interactions, potential chemical signals, and the role that red:far-red ratios may play in clonal communication and competition.