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

Both genetic and environmental factors can determine whether an invasive pl ant species will establish. To determine how these factors influence the es tablishment of the invasive grass Phalaris arundinacea L. (reed canary gras s), we grew three genotypes in 10 artificial environments and asked how a g enotype'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 c onditions did significantly affect growth. Individual plants produced more aboveground and belowground biomass when grown singly than they did when gr own with competitors. The identity of neighboring competitors had no effect . Although genotype had no significant efffect, there was a significant gen otype x environment interaction. Clone 1 produced more root biomass than ei ther clone 2 or clone 3 when there was no or little competition, but in com petitive 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 bec ause it could preferentially allocate more biomass to roots. The presence o f three growth patterns from such a small, localized sample suggests that d ifferent growth strategies are probably common within populations of reed c anary grass and may be important for allowing reed canary grass to successf ully invade new habitats.