RAPD markers reveal diversity within and among clonal and seedling stands of aspen in Yellowstone National Park, U.S.A.

Fire in 1988 created a situation that allowed a rare aspen seedling recruitment event to occur within Yellowstone National Park. Through the use of (i) 194 randomly amplified polymorphic DNA (RAPD) markers from 14 select primers, (ii) measures of population diversity, and (iii) neighbor-joining analysis it was determined that the postfire aspen seedling population contains greater diversity within each of the four sampled stands than that found within all of the 10 sampled mature aspen stands that pre-existed the fire. Unlike previous studies, a large portion of the molecular variation in both the seedling and mature populations was partitioned among stands. Furthermore, variation was unexpectedly detected among ramets within each mature stand. The mature stands appear to be clonally derived, yet individual ramets within stands varied slightly and incrementally in their RAPD profile. These data suggest that somatic mutations may be occurring and accumulating in clonal aspen stands. A proposed scenario of stand establishment and development involving the accumulation of somatic mutations and elimination of genetically related seedlings arising from a rare founder event provides the theoretical basis for the observed differences among and within seedling and mature stands of aspen in Yellowstone National Park.