The population genetics of an important invasive species in the Prairie Pothole Region; Kentucky bluegrass (Poa pratensis)

Background/Question/Methods

Kentucky bluegrass (Poa pratensis) is an invasive species from Eurasia introduced during early European settlement of North America.  Kentucky bluegrass (KBG) has been studied extensively as an economic crop, but has not received much attention from ecologists despite its destructive potential as an invasive species in the prairie pothole region (PPR).  Recent reviews describe plant introduction and naturalization, but genetic data from a variety of invasive events is necessary to fully understand the mechanisms of invasion in this species.  KBG is aggressively invading and altering the character of prairie communities in North and South Dakota.  I am studying the genetic diversity, growth characteristics and ploidy in this region using 12 microsatellite markers at 19 sites with the goals of elucidating 1) the level of population structuring and diversity in its invasion, 2) the variation of polyploidy in the wild genotypes, and 3) competitive ability in wild populations. My results have implications for management and policy decisions regarding native prairie and may provide a tool for understanding and controlling this and other invasive species. 

Results/Conclusions

A total of 665 samples were evaluated at 12 microsatellite loci along with species richness and degree of invasion at each site.    KBG is the most abundant plant species in the PPR and its abundance (greater than 50% composition) is negatively correlated with species richness.  There is a high degree of genetic diversity and ploidy levels within even a single sampled site at all 12 loci.  The number of alleles at each locus range from one to thirteen. The ploidy levels range from 2n to at least 36n with varying frequencies of ploidy levels and genetic diversity between and among sites.  There is evidence that certain genotypes are associated with greater percentages of invasion and ploidy may be segregating along a perception gradient.  These results suggest that some large genomic changes as a result of autopolyploid and propagule pressure can influence the success of the KBG invaders and potentially other invasive species.