The most geographically limited and perhaps most unusual plant communities in Great Smoky Mountains National Park (GRSM) are the high-elevation “beech gap” forests. Beech gaps are dominated by Fagus grandifolia (American beech) and occur as “deciduous islands” in spruce-fir forests above 1370 m. The beech gaps appear to be morphologically and ecologically distinct from beech stands at lower elevations in GRSM. Because of their morphological appearance, clonal reproduction in response to harsh environmental conditions has been assumed to be the driving force in maintaining these populations. Recent work on this subject using inter-simple sequence repeat (ISSR) molecular markers revealed a potentially more complex system than was previously assumed. The frequency of clonal reproduction varied across sites and was not consistently more frequent in the higher elevation beech gap populations. The results of this previous work indicate that disturbance appears to be the factor driving variation in the frequency of clonality in this woody species. Here we revisit this question with the goal of forming a regional focus to be included in a larger range-wide phylogeographic study of the species. Using amplified fragment length polymorphisms (AFLPs), we investigated clonal structure within and among six populations of F. grandifolia in GRSM. These populations were selected based on site aspect, canopy cover, elevation, and intensity of disturbance induced by beech bark disease. In addition, we used AFLPs to assess the rate of somatic mutation in this species as a way to address concerns regarding our ability to identify clonal genotypes in a long-lived species.

Key words: AFLPs, clonal reproduction, Fagus grandifolia, somatic mutation