RAPD VARIATION IN RELATION TO POPULATION-SIZE AND PLANT FITNESS IN THE RARE GENTIANELLA-GERMANICA (GENTIANACEAE)

We investigated the distribution of genetic variation and the relation ship between population size and genetic variation in the rare plant G entianella germanica using RAPD (random amplified polymorphic DNA) pro files. Plants for the analysis were grown from seeds sampled from 72 p arent plants in II G. germanica populations of different size (40-5000 fruiting individuals). In large populations, seeds were sampled from parents in two spatially distinct subpopulations comparable in area to the total area covered by small populations. Analysis of molecular va riance revealed significant genetic variation among populations (P < 0 .001), while genetic variation among subpopulations was marginally sig nificant (P < 0.06). Average molecular variance within subpopulations in large populations did not differ significantly from whole-populatio n values. There was a positive correlation between genetic variation a nd population size (P < 0.01). Genetic variation was also positively c orrelated with the number of seeds per plant in the field (P < 0.02) a nd the number of flowers per planted seed in a common garden experimen t (P < 0.051). We conclude that gene Row among natural populations is very limited and that reduced plant fitness in small populations of G. germanica most likely has genetic causes. Management should aim to in crease the size of small populations to minimize further loss of genet ic variation. Because a large proportion of genetic variation is among populations, even small populations are worth preserving.