Evidence for recent evolution in Microstegium vimineum in North America
Microstegium vimineum (Poaceae; EPPO List of Invasive Alien Plants) is an annual grass species native to Asia and recorded as invasive in North and Central America, and within the EPPO region (Azerbaijan, Georgia, Russia (Northern Caucasus) and Turkey). To evaluate if plant growth parameters varied in response to abiotic parameters, seed was collected from 3 distinct mid-Atlantic populations in the US. Under controlled conditions, growth experiments were conducted. Plant replicates were exposed to four environmental treatments where each treatment had varying levels of sunlight and nutrient addition. Plant growth parameters were measured at the end of the experiment where biomass measurements were taken for leaves, stems, roots and seeds. In addition total leaf area was recorded for each plant replicate. Significant effects were observed for leaf area, leaf weight, stem weight and total weight as a function of population, light and nitrogen levels. The degree of variation in seed production and biomass among populations grown in the experiment was highly correlated to growing season length and cumulative day degrees recorded near each population location indicating adaptive evolution. This high level of phenotypic plasticity would help the species to colonies diverse ecological niches increasing its invasiveness in fragmented habitats. In 2014, EPPO conducted a pest risk assessment on Microstegium vimineum and the PRA is currently undergoing peer review.
Sources
Ziska LH, Tomecek MB, Valerio M, Thompson JP (2015) Evidence for recent evolution in an invasive species, Microstegium vimineum, Japanese stiltgrass. Weed Research 55, 260-267.