Abstract Sympatric local populations of leptosporangiate ferns found to vary in phenotypic tolerances of environmental variation in the common habitat were surveyed for allozymes as indicators of genetic variation. Each local population was also surveyed for pattern of ramet distribution. The species with the greater phenotypic tolerances, Deparia acrostichoides, was found to be more variable genetically than the species with lower phenotypic tolerances, Diplazium pycnocarpon. Levels of genetic variation among the two species indicated that Deparia acrostichoides is a late-successional species and Diplazium pycnocarpon is an early-successional species, in agreement with a previous prediction. Ramet distribution patterns indicated a greater effect of intraspecific competition among ramets of Diplazium pycnocarpon than among ramets of Deparia acrostichoides.