Assessment of genetic variation and population differentiation in invasive multiflora rose, Rosa multiflora Thunberg (Rosaceae) in northeastern Ohio

In this study, I examined genetic diversity and levels of population differentiation between eight populations of the invasive plant multiflora rose (Rosa multiflora Thunberg Ex. Murray) located in Portage and Summit Counties, in northeastern Ohio. I used six microsatellite marker loci to determine allelic diversity, percent polymorphic loci, and expected and observed heterozygosity. My results show that multiflora rose populations included have moderate levels of genetic variation. I found a total of twenty five alleles in the six microsatellite loci that were examined. On an average, there were 4.16 alleles per locus, but the average number of alleles per locus observed in each population ranged between 1.66 and 3.33. Effective number of alleles ranged between 1.38 and 2.17, indicating variation in allele frequencies among loci. Average observed heterozygosity (H O = 0.15) was less than expected heterozygosity (HE = 0.43) across all but one population. This trend of heterozygosity deficiency and F statistics results indicate significant level of inbreeding in the studied populations. Most of the loci failed to conform to Hardy-Weinberg expectations in all populations indicating forces of evolution interacting. Analysis of molecular variance revealed significant levels of genetic differentiation between populations. Nei's unbiased estimators of genetic distance range from nearly 0 to 0.59, indicating high genetic differentiation. These findings are then discussed in the light of ecological and historical considerations.