THE FUNGUS ARMILLARIA-BULBOSA IS AMONG THE LARGEST AND OLDEST LIVING ORGANISMS

ASEXUALLY reproducing organisms occur in a variety of taxa in all biological kingdoms 1 and distinguishing asexually propagated genotypes is essential for the understanding of their population biology. Among the higher fungi, however, the clonal 'individual' is especially difficult to define 2 because most of the fungal thallus consists of a network of anastamosing hyphae embedded in the substratum. Whether fruit-bodies, the most recognizable part of a fungus, are produced by a single supporting mycelium can only be determined by establishing direct physiological continuity or genetic identity. We report a means by which individual fungi can be unambiguously identified within local populations and identify an individual of Armillaria bulbosa that occupies a minimum of 15 hectares, weighs in excess of 10,000 kg, and has remained genetically stable for more than 1,500 years.