Inflorescences of Neotropical herbs as a newly discovered microhabitat for myxomycetes

Abstract

An assemblage of myxomycetes associated with inflorescences of large Neotropical herbs, a microhabitat not previously known to support these organisms, is described and characterized ecologically from a number of study sites in Costa Rica, Ecuador, and Puerto Rico. Thirty-one different taxa were found among 652 specimens of myxomycetes recorded in the field or obtained from 358 moist chamber cultures prepared with decaying floral parts. A comparison with the results of 696 moist chamber cultures prepared with various other litter substrates showed that thirteen myxomycete taxa occurred more often on inflorescences. Six taxa had a strong preference for this microhabitat, and three of those seem to be new for the Neotropics. Correspondence analysis of the data set compiled for inflorescences indicated that the assemblage of myxomycetes was relatively consistent across all of the various study sites. The actual myxomycete substrates were the rapidly decaying floral parts enclosed by the massive, still living bracts. Richest in myxomycetes were species of Heliconia and Costus. Here, nectar residuals probably promoted a rapidly developing community of yeasts and bacteria. A high density of these organisms was indicated by the frequent occurrence of myxobacteria in the moist chamber cultures prepared with floral parts. Results from canonical correspondence analysis suggested that a substrate pH between 8 and 9 and the presence of massive, compact inflorescences on plants occurring at lower elevations in localities with moderate annual rainfall provide optimal conditions for inflorescence-inhabiting myxomycetes. An incidental dispersal of myxomycete spores by birds that pollinate the flowers or feed upon the fruits seems possible and may have accounted for the high degree of preference exhibited by some of the inflorescence-inhabiting myxomycetes, for which the term “floricolous” is proposed.

• dispersal
• ecology
• inflorescence
• Neotropics
• slime molds

We are indebted to Mike Dilger, the resident biologist of the Maquipucuna Cloud Forest Reserve, for identifying the bird species visiting Costus guanaiensis, and the staff of the herbarium of the Pontifical Catholic University of Ecuador in Quito (QCA) for providing comparison material for identification of some of the species of Heliconia investigated. For help in organizing field work in Puerto Rico, we wish to thank Dr. D. Jean Lodge (USDA Forest Service, Sabana work station). This research was supported by a grant from the National Science Foundation (DEB-9705464), with additional funding from the National Geographic Society (Grant #6050–97).