Environmental and genetic effects on the early survival and growth of the invasive grass Phalaris arundinacea

Abstract

Both genetic and environmental factors can determine whether an invasive plant species will establish. To determine how these factors influence the establishment of the invasive grass Phalaris arundinacea L. (reed canary grass), we grew three genotypes in 10 artificial environments and asked how a genotype's growth and survivorship was affected by environmental conditions. We found that genotype strongly influenced survivorship, but there was no significant effect of environment on survivorship. However, environmental conditions did significantly affect growth. Individual plants produced more aboveground and belowground biomass when grown singly than they did when grown with competitors. The identity of neighboring competitors had no effect. Although genotype had no significant efffect, there was a significant genotype × environment interaction. Clone 1 produced more root biomass than either clone 2 or clone 3 when there was no or little competition, but in competitive neighborhoods, clone 3 allocated relatively more biomass to roots than to shoots. Under ideal conditions in the greenhouse, clone 2 produced more tillers than the other two clones. Based on these results, it appears that clone 1 may have an advantage under sparse vegetative cover, but clone 3 may have a competitive advantage in highly competitive neighborhoods because it could preferentially allocate more biomass to roots. The presence of three growth patterns from such a small, localized sample suggests that different growth strategies are probably common within populations of reed canary grass and may be important for allowing reed canary grass to successfully invade new habitats.