Variation in a Natural Population of Schizophyllum commune

Abstract

When a sample of 77 wild dikaryotic isolates from an extremely local population (ca. 1,000 fruit bodies in less than 100 sq yards) was examined by biometrical methods, considerable variation was present in growth rates (at 20⚬, 25⚬, 30⚬ C) and fruiting characteristics (fruiting time and number of fruit bodies) of the isolates, and in their cultural and fruit-body morphology. This evidence, together with the identification of 12 distinct dikaryotic combinations of six A and six B incompatibility factors in 12 isolates, indicates a highly variable population consisting of a large number of genetically unique dikaryons. The growth rate distributions of the isolates support the view that this character is subject to stabilizing selection in nature (Simchen 1966b). The distributions for fruiting time and number of fruit bodies are suggestive of directional selection, with a stabilizing component, toward early fruiting and small numbers of fruit bodies. Correlations were demonstrated between two fruiting characters (fruiting time and number of fruit bodies) and growth rate at 20⚬, but not with growth rate at 25⚬ or 30⚬. Fruiting time was correlated with number of fruit bodies; the distributions of these two characters also appeared to be related to fruit-body morphology.