Poa bulbosa L. is a small perennial bunchgrass that possesses a wide distribution throughout Western Europe and the Mediterranean. This grass has been introduced into North America and now occurs throughout much of the western United States, particularly in the Intermountain West. In its native range, P. bulbosa reproduces through both sexual and asexual means; however, in its introduced range in the Intermountain West it primarily reproduces clonally through the production of bulbils. Also, high chromosome numbers are frequently reported, suggesting that this grass is a polyploid. Using enzyme electrophoresis, we analyzed 10 populations of P. bulbosa from Idaho, Oregon and Washington by staining for 14 enzymes that were coded for by 19 putative loci. Our results indicate that P. bulbosa contains higher levels of genetic variation than would be expected for an introduced clonal plant species: 27.9% of loci are polymorphic per population, with an average of 1.54 alleles per locus, and a mean observed heterozygosity of 0.202. The high levels of heterozygosity observed for this grass are consistent with previous reports for autopolyploid plant species. Finally, the complex distribution of multilocus genotypes exhibited by P. bulbosa suggests the possibility of multiple introductions of this species into its new range.

Key words: allozyme variation, clonal reproduction, introduced plant, multilocus genotypes, Poa bulbosa, Poaceae