Diversity of wood-inhabiting fungi in Panamanian tropical rain forest

Wood-inhabiting ascomycetes and basidiomycetes represent a diverse group of taxa which play an important role in decomposition and nutrient cycling. Relatively little is known about how communities of these organisms are organized or how the diversity or abundance of host species influences community structure. In this study, the composition of ascomycetes and basidiomycetes was examined on known host tree species in seasonally moist and seasonally inundated lowland tropical forests in central and eastern Panama. To examine the effect of host identity, tree data from a permanent plot on Barro Colorado Island (BCI) were used to examine fungal communities on three host species: Prioria copaifera, Quararibea asterolepis, and Trichilia tuberculata . Fungal diversity was high. Sampling of 181 trees and branches yielded a total of 75 ascomycete and 112 basidiomycete species. Total diversity on these hosts is substantially higher as the asymptote of species accumulation curves was not reached. Ordination revealed some consistent differences in fungal communities among hosts, and randomization tests showed that there were significantly fewer generalist ascomycete fungi than expected at random, indicating some host preference exists. The most abundant fungal species however were generalists found on all hosts. To examine the effect of host abundance and forest type, fungal communities were compared on a single host ( Prioria copaifera) occurring at low and high abundance in five forest stands. Highest fungal diversity was found on the host where it occurred at low density in high diversity forest. However, communities of both fungal groups at every site were dominated by a few abundant species that were widely distributed across forest stands. Community composition also varied according to the size of the host resource. A positive correlation was found between resource size and fungal diversity for basidiomycetes at all sites and for ascomycetes at three of five sites. This effect was corroborated by results from an experiment in which resource size was varied using wood blocks. While common basidiomycetes fruited on both small and large blocks, rare species were restricted to large block sizes.; These results reveal that host identity, tree diversity, and forest architecture (influencing resource size) are all important determinants in community structure of wood-inhabiting fungi.