THE POPULATION BIOLOGY OF 2 LITTER DECOMPOSING AGARICS ON A SOUTHERN APPALACHIAN MOUNTAIN

Two litter decomposing agarics, Collybia subnuda and Marasmiellus prae acutus, were intensively sampled on permanent plots on a southern Appa lachian mountain. Collybia subnuda is a dominant decomposer of deciduo us tree detritus and M. praeacutus is a dominant decomposer of conifer ous detritus. Tests of somatic incompatibility indicate that the obser ved population densities of C. subnuda and M. praeacutus are not less than 3.9-9.3 genets/100 m2 and 7.1-12.1 genets/100 m2, respectively. S elf-crosses of single spore isolates obtained from both species indica te that C. subnuda has a bipolar mating system and M. praeacutus is te trapolar. This is the first report of a bipolar mating system in the g enus Collybia. Tests of somatic incompatibility between synthesized di karyons and their parent progenitor indicate that somatic incompatibil ity tests can discriminate between closely related genets in some spec ies but cannot in others.