PATTERNS OF GENETIC-VARIATION DETECTED BY RAPD SUGGEST A SINGLE ORIGIN WITH SUBSEQUENT MUTATIONS AND LONG-DISTANCE DISPERSAL IN THE APOMICTIC FERN DRYOPTERIS-REMOTA (DRYOPTERIDACEAE)

Debates on speciation processes in pteridophytes have revived. In orde r to study the evolutionary origin of an apomictic fern species, we in vestigated the genetic variation in the strictly agamosporous Dryopter is remota. We determined the genotypes of 22 individuals from many dif ferent locations within the species' European distribution and of 20 i ndividuals from a Swiss population. A previous study on isozyme variat ion showed no intraspecific genetic variation in a similar sample set (Schneller and Holderegger, 1994, America Fern Journal 84: 94-98). In contrast to this, four out of 12 random amplified polymorphic DNA (RAP D) primers tested revealed low genetic diversity among individuals of D. remota from different locations. Intrapopulational genetic variatio n was also very low, but in the single population studied, a unique mu ltiband genotype could be detected. The geographic distribution of gen etic Variation found in D. remota was best explained by the assumption of a single origin, the accumulation of somatic mutations during spre ad, and occasional, but effective, events of dispersal over large dist ances. The present study thus stresses the importance of long-distance dispersal in evolutionary processes and biogeography of ferns.