Migration and population divergence of invasive, polyploid Kentucky bluegrass (Poa pratensis), in northern prairies

Background/Question/Methods

The study of invasive species is essential for conservation efforts.  In particular, polyploidy is thought to be an important feature of invasive species, but has been difficult to study until recently.  We sought to characterize the wild, invasive Poa pratensis in the northern Great Plains—a species which in cultivation varies from 28 to 140 chromosomes.  We used flow cytometry and microsatellite markers to ascertain whether Poa pratensis is continually escaping into the wild. 

Results/Conclusions

Across all tested wild populations, high levels of genetic diversity (H_S = 0.823-0.906) were detected along with moderate levels of structure (Rho_ST=0.1263; p-value =0.000).  Non-significant pairwise Rho_ST values revealed a pattern of gene flow which followed predominant wind directions during pollination.  When we compared the wild individuals to commonly planted commercial varieties, we found virtually no genetic overlap across all tests, which did not support our hypothesis of continual escape of propagules from urban into wild populations.  Furthermore, DNA content tests indicated a narrow range in wild populations compared to commercial varieties further supporting a hypothesis of divergence between wild and commercial varieties.  These results indicate, despite the common planting of Poa pratensis, the wild, invasive variety is a naturalized strain.