Evidence for recent adaptative evolution in mid-Atlantic populations of an invasive exotic grass, Microstegium vimineum, Japanese stiltgrass

Authors: Ziska, Lewis; Tomecek, Martha; VALERIO, MARIA - University Of Basilicata; THOMPSON, JOHN - Foundation For The Study Of Invasive Species

Submitted to: Weed Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2014
Publication Date: 5/1/2015
Citation: Ziska, L.H., Tomecek, M.B., Valerio, M., Thompson, J.P. 2015. Evidence for recent adaptative evolution in mid-Atlantic populations of an invasive exotic grass, Microstegium vimineum, Japanese stiltgrass. Weed Research. 55:260-267.

Interpretive Summary: The establishment and spread of invasive plants does great economic and environmental harm, costing the United States over 2 billion dollars per year. Consequently it is of interest to understand how such plants become established and spread. One such plant is Microstegium vimineum, or Japanese stiltgrass, which has become established throughout the mid-Atlantic region, including many national parks. In this study we examined seed from three mid-Atlantic populations of Japanese stiltgrass, to assess growth and seed yield responses to light and nitrogen under greenhouse conditions. In addition we examined evolutionary potential by determining if the growth and seed yield of a population was correlated to the growing conditions (e.g., temperature) where the seed was collected. Differing growth and seed production indicated considerable variation between M. vimineum populations. Interestingly, the degree of variation of seed production and final biomass among populations was, in fact, strongly correlated with growing season length and cumulative degree days recorded near each population location. These later data indicate that M. vimineum, introduced into this region less than 100 years ago, may be undergoing rapid adaptive evolution. Overall, this study suggests that adaptation may be an important aspect in the establishment and spread of this invasive species. Whether rapid evolutionary adaptation is a common strategy among all invasive plants remains to be tested. This information will be of interest to Park Rangers, land managers, ecologists and visitors to national parks.

Technical Abstract: The establishment and spread of invasive plants has often been associated with a ‘general-purpose genotype,’ and a corresponding high degree of phenotypic plasticity when introduced to a new environment. However, changes in evolutionary potential of invasive species need to be considered in addition to phenotypic variation; as such changes can facilitate rapid range expansion. In this study we utilized seed from three mid-Atlantic populations of a widespread invasive species, the Asian flowering annual grass, Microstegium vimineum, (Japanese stiltgrass), to assess if populations varied in their biomass and reproductive responses to light and nitrogen under greenhouse conditions. To assess adaptation, we quantified and correlated the abiotic environment from each collection location with the final biomass and seed production of that population in the greenhouse. Under greenhouse conditions, significant population by light interactions were observed for most vegetative, and all reproductive parameters measured, whereas significant population by nitrogen interactions were only observed for seed number. Differing growth and reproductive responses to a common set of abiotic parameters (e.g. light), indicated considerable variation between M. vimineum populations. Interestingly, the degree of variation of seed production and final biomass among populations was strongly correlated with growing season length and cumulative degree days recorded near each population location. These later data indicate that M. vimineum, introduced into this region less than 100 years ago, may be undergoing rapid adaptive evolution. Overall, this study suggests that adaptation may also be an important aspect in the establishment and spread of this invasive species.