VIGOR AND SURVIVAL OF INBRED AND OUTBRED PROGENY OF ATHYRIUM-FILIX-FEMINA

Morphology and mortality of sporophytes resulting from intergametophyt ic and intragametophytic mating were studied in the fern Athyrium fili x-femina. In a long-term experiment, we determined the relevance of he terosis and/or genetic load in this homosporous fern species. Progeny from intergametophytic crossing, probably consisting of heterozygous i ndividuals, exhibited most vigorous growth, small morphological variat ion, and low mortality. Progeny resulting from intergametophytic selfi ng, likely to include individuals with various levels of homozygosity, showed larger morphological variation, higher mortality, and smaller mean leaf length. Progeny from intragametophytic selling (completely h omozygous) had the smallest mean leaf length, highest mortality, and c onsiderable morphological variation. These results for a homosporous f ern species agree with theoretical and empirical studies on heterosis and genetic load in flowering plants.