Experimental and simulation studies of the population genetics, water relations, and vegetative growth of Phalaris arundinacea

Research into diverse areas such as population genetics and ecology is needed to understand the invasion process. The population genetic structure of invasive plants is influenced by demographic history, with events such as population bottlenecks and human mediated dispersal resulting in distinctive molecular signatures. Ecological traits such as growth rate or tolerance to flooding and drought help to determine whether an introduced species will become invasive. Phalaris arundinacea L. is a perennial, cool season grass native to Europe and North America that has become an invasive pest, primarily in North American wetlands. To study genetic and ecological aspects of invasion in P. arundinacea, a series of empirical and simulation studies were carried out.;Inter-simple sequence repeat markers were used to infer the population genetic structure of North American and European populations of P. arundinacea. Most of the genetic variation was found to be within, as opposed to among, populations of P. arundinacea, possibly as a result of its breeding system and history of human mediated dispersal. Populations from different regions were not strongly differentiated from one another, reflecting the presence of one large, panmictic metapopulation with a high level of neutral genetic variation. Simulated dominant marker genomes were used to validate the genetic analyses used and to determine the minimum number of loci required for the popular analysis of molecular variance and STRUCTURE algorithms.;Greenhouse and field studies were used to study its responses to drought and growth in dry conditions, and assess the level of genetic variation in drought- tolerance traits. Genotypes were found to be significantly different for many traits, and surprisingly, had the highest growth rates in upland conditions. Differences in some traits were found for upland and wetland habitats of origin, possibly indicating local adaptation.;Cellular automata and differential equations are two techniques that have been used to model biodiversity. A tradeoff between competition and colonization in these models is essential for the stable coexistence of many species. The techniques employed in these models can be adapted to study intraspecific competition and diversity. The growth rate data from the field experiment was used to calibrate cellular automata and differential equation models of vegetative growth. Multiple genotypes coexisted in all models at intermediate levels of habitat disturbance, which may help to explain the high diversity observed in invasive monocultures of P. arundinacea.