Genetic variation in running buffalo clover (Trifolium stoloniferum: Fabaceae) using random amplified polymorphic DNA markers (RAPDs)

Trifolium stoloniferum Muhl. es Eaten (Fabaceae), a perennial, stoloniferous herb commonly known as running buffalo clover, once occurred over a large area in the Midwest (U.S.A.) but is currently restricted to five states and is federally endangered. The purpose of this study was to examine genetic variation within and among populations of T. stoloniferum throughout its known geographic distribution using Random Amplified Polymorphic DNAs (RAPDs) as markers. The average within-population banding similarity values for 390 individuals from 21 populations are high, ranging from 0.920 to 0.984 (mean = 0.952). The mean banding similarities for comparisons between populations range from 0.856 to 0.902 (mean = 0.884), implying that much of the diversity resides among populations in this species. There are also differences in average similarities within and between patches at the population level, suggesting substructuring within populations. A large proportion of plants sampled within populations have different banding patterns, indicating that populations do not consist of one to several genets perpetuated vegetatively by stolons. Our results agree with those of previous workers using allozymes in showing relatively low levels of diversity within populations and in the species as a whole. However, in the present study RAPD-marker variation was detected in all populations, with levels of diversity in several smaller populations equal to those in larger ones; no allozyme variation was detected in half of the populations sampled, and smaller populations were often monomorphic. Two bands are unique to Missouri populations and one band was found only in Ohio populations. Allozyme data were used to suggest that conserving smaller populations could be of lower priority because they lack diversity; certain ones are identical to each other, and thus they may consist of single genets. By contrast, RAPDs show that even the smallest populations have a high proportion of different genets and thus are worthy of further consideration for conservation.