Evolutionary and demographic processes in the invasive grass Microstegium vimineum (Japanese stiltgrass)

Background/Question/Methods

Microstegium vimineum (Trin.) A. Camus (Japanese stiltgrass) is considered among the most invasive plants in the eastern United States. There has been considerable study of this species' ecology and management though far less attention has been paid to its molecular ecology and the evolutionary processes that may influence its invasion success. Here, we describe M. vimineum's genetic population structure and diversity in both its native and introduced ranges using a microsatellite marker system.

Results/Conclusions

We found clear signals that M. vimineum's mixed cleistogamous/chasmogamous mating system is the most important determinant of the species' population structure and variability. The invasive range had lower genetic diversity overall, probably due to founder effects. Also, population and regional genetic differentiation appeared to be "in process" in the invasive range. Furthermore, M. vimineum's mating system allowed for the near fixation of microsatellite genotypes in a given population by high rates of selfing, while still permitting the persistence of allelic diversity and generation of new genotypes at low frequency via occasional outcrossing. Thus, this mating system may confer adaptive advantage to the species as it settles upon fit genotypes in a given area while retaining evolutionary potential for range expansion into new habitats.