COMPETITIVE RESPONSE OF NATIVE SOLIDAGO ALTISSIMA (LATE GOLDENROD) AND INVASIVE TANACETUM VULARE (COMMON TANSY) DIFFER ACCORDING TO PLOIDY AND GENOTYPE

Abstract

It is becoming increasingly important for us to understand the ability of native plant populations to tolerate competition by invasive species that are becoming pervasive in native plant communities. The ability to contend with the presence of an invader may depend on the genetic structure of both the native and invading population. This study examines the roles of polyploidy, genetic variation in growth traits, and variation in plasticity in response to the presence of a competition in determining competitive outcomes. I examined the genetic architecture from both sides of the competitive interaction between native diploid and tetraploid genotypes of <italic>Solidago altissima</italic> (late goldenrod) and genotypes of the invasive species <italic>Tanacetum vulgare</italic> (common tansy). In this study, both ploidy level and the specific genotype within ploidy level of <italic>S. altissima</italic> influenced the outcome of the competitive interaction, with tetraploids being better able to suppress the growth of the invasive species to a greater extent than diploids. In addition, some tetraploid genotypes expressed adaptive plasticity such that they were able to tolerate the presence of <italic>T. vulgare</italic> and maintain growth. Similarly, genotypes of T. vulgare differed in their competitive ability when paired with diploid or tetraploid <italic>S. altissima</italic>. Overall, this work suggests that both species possess genetic variation such that competitive ability may evolve in response to the presence of the other species. This underscores the importance of examining both sides of a competitive interaction to understand the complex evolutionary dynamics that occur between native and invasive plant species.