Myxomycetes Associated with the Aerial Litter Microhabitat in Tropical Forests of Northern Queensland, Australia

One surprising result from recent studies carried out in Neotropical moist forests is that myxomycete biodiversity seems to be greatest in microhabitats located above the ground, whereas in temperate and boreal forests it is greatest in microhabitats associated with the forest floor. Myxomycetes appear to be organisms adapted to highly fluctuating conditions of environmental moisture, but continuously high moisture levels apparently do not favor their growth and development. In addition to their apparent displacement from forest floor (relatively moist) to aerial (relatively drier) microhabitats, the majority of the myxomycetes encountered in Neotropical moist forests are characterized by a phaneroplasmodium, which is robust, can achieve considerable size in some species, and appears to tolerate the two extremes of the moisture gradient better than the other types of plasmodia found in myxomycetes. The objective of the present study, which is still ongoing, was to investigate the quantitative ecology and distributional relationships of myxomycetes associated with aerial litter microhabitats in tropical forests of northern Queensland, Australia. More than 90% of the 69 moist chamber cultures prepared with samples of aerial litter collected from two study sites yielded some evidence (either plasmodia or fruiting bodies) of myxomycetes. Didymium squamulosum was the single most abundant species, with Physarum compressum and Physarum pusillum also important. All three of these are among the more characteristic myxomycetes associated with aerial litter in Neotropical forests, which suggests that the aerial litter microhabitat may support compositionally similar assemblages of species in the tropical moist forests of Australia.