A compilation of studies using RAPD

A compilation of studies using RAPD markers for evaluating population differentiationresulted in 78 estimates of AMOVA-derived ΦST and 31 estimates of Nei's GST, as wellas in 41 estimates of Nei's within-population diversity. In outcrossing taxa, estimatesof between-population diversity were closely correlated with maximum geographicdistance between sampled populations. A corresponding association was not found inselfing taxa. These results suggest that RAPD can be a sensitive method for detection of genetic structuring according to the isolation-by-distance model. However, italso means that sampling strategies, as applied in individual studies, can seriously influence the resulting estimates of between-population diversity. Other samplingstrategies, like number of plants per population and number of scored polymorphicmarkers, do not seem to impart any serious artefacts. As previously verified with allozyme data, RAPD markers showed that long-lived, outcrossing, late successionaltaxa retain most of their genetic variability within populations. By contrast, annual,selfing and/or early successional taxa allocate most of the genetic variability amongpopulations. Estimates for between- and within-population diversity, respectively,proved to be negatively correlated, as previously reported for allozyme data. The onlymajor discrepancy between allozymes and RAPD markers concerns geographicrange; within-population diversity was strongly affected by distributional range of theinvestigated species in the allozyme data but not in the RAPD data. Moreover, RAPDbased values for between-population diversity increased with increasing distributionalrange whereas the opposite has been reported in a large allozyme data compilation.Contrary to allozymes, RAPD marker-derived within-population diversity is probablytherefore not a very good predictor of total species genetic diversity.