Evidence for the hybrid origin of Nuphar xrubrodisca (Nymphaeaceae).

Plants intermediate in appearance between Nuphar microphyllaand N. variegata (Nymphaeaceae) have long been assumed to bethe result of hybridization. The evidence for this is based primarilyon field observations of morphology, poor fruit production, closegeographical proximity of presumed parent species, and limited pollensterility data. Fertile populations of the same plants have also beendocumented. We employed multivariate analyses of morphology, pollenfertility studies, and random amplified polymorphic DNA (RAPD) markersto test the hypothesis that Nuphar × rubrodiscarepresents a natural interspecific hybrid between N.microphylla and N. variegata. Examination of 15morphological characters demonstrated the intermediacy of N.× rubrodisca between N. microphylla and N.variegata, and the pollen data revealed a markedly lower meanpollen viability in N. × rubrodisca (23%)compared to the other two species (91 and 86%, respectively). Eight 10-mer primers produced 13 species-specific RAPD markers forN. microphylla and nine for N. variegata, with all 22markers present in N. × rubrodisca. The datafrom RAPDs are concordant with morphology in implicating N.microphylla and N. variegata as parents of N.×rubrodisca.