Population genetic study in the Balearic endemic plant species Digitalis minor (Scrophulariaceae) using RAPD markers

Digitalis minor (Scrophulariaceae) is a cardenolide-producing plant endemic to the eastern Balearic Islands (Mallorca, Menorca. and Cabrera) that occu rs in two morphologically distinct varieties: D. minor var. minor (pubescen t) and D. minor var. palaui (glabrous). Levels and patterns of genetic dive rsity in 162 individuals from 17 D. minor populations across the entire geo graphic range were assessed using random amplified polymorphic DNA (RAPD) m arkers. Comigrating RAPD, fragments tested were found to be homologous by S outhern hybridization in both var. minor and var. palaui. To avoid bias in parameter estimation. analyses of population genetic structure were restric ted to those RAPD, bands that fulfilled the 3/N criterion (observed frequen cies were less than 1 - (3/N] in each population) either among or within ea ch island. Analyses of molecular variance (AMOVAs) with distances among ind ividuals corrected for the dominant nature of RAPD (genotypic analysis) sho wed low values (1.57-17.55%) of between-population variability, indicating a relatively restricted population differentiation as expected for an outcr ossing species such as D. minor. Nested AMOVAs demonstrated. however. a not significant partitioning of genetic diversity among Mallorca, Menorca, and Cabrera islands. Estimates of the Wright, Weir, and Cockerham and the Lync h and Milligan F-ST from null allele frequencies corroborated AMOVA partiti oning and provided evidence for population differentiation in D, minor. Our RAPD data did not show significant differences between pubescent and glabr ous populations of D. minor, suggesting a failure to find a correlation bet ween the RAPD loci and this morphological trait.