Ecological succession of dictyostelid slime molds on the island of Hawai'i

Patterns of ecological succession have been demonstrated for decomposer communi- ties, but the details of such patterns with respect to the role of eumycetozoans have not been addressed. Successional patterns can be inferred from a sequence of closely located sites which dif- fer only in age, but are controlled for other sources of variation. Hawai'i, the largest and youngest of the Hawaiian Islands, offers an ideal site for such studies, consisting of variously-aged land- forms underlain by similar substrates, and influenced by similar climates and biotic communities. Soil/litter samples were collected from nine montane mesic sites of similar elevation and rainfall, but ranging in substrate age from 67 to 10,000 ybp. Samples were processed to recover dictyostelid (cellular) slime molds according to established protocols. Results suggest that slightly different assemblages of dictyostelids occupy the soil/litter derived from different-aged parent materials. The density and species diversity of dictyostelids was higher in soil/litter samples from the youngest sites. The time necessary for dictyostelids to colonize a site is less than 67 years. It is hypothesized that colonization of the soil/litter by dictyostelids is followed by the arrival of predators, particu- larly nematodes, which adversely affect the density and species diversity of soil amoebae in gener- al, and dictyostelids in particular.