A. Elizabeth ARNOLD1
*, Zuleyka MAYNARD2
and Gregory S. GILBERT3
" Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA.
# Smithsonian Tropical Research Institute, Barro Colorado Island, Apartado 2072, Balboa, RepuT blica de PanamaT.
$ Department of Environmental Studies, University of California, Santa Cruz, CA 95064, USA.
Received 30 September 2000; accepted 12 January 2001.
Fungal endophytes have been found in every plant species examined to date and appear to be important, but largely unquantified,
components of fungal biodiversity. Endophytes are especially little known in tropical forest trees, where their abundance and
diversity are thought to be greatest. Here, we explore the occurrence of endophytes in a broad diversity of woody, angiospermous
taxa in a lowland, moist tropical forest in central Panama! . We use similarity indices to assess host preference and spatial
heterogeneity of endophytes associated with two co-occurring, but distantly related, understorey tree species in two sites of that
forest, and assess the utility of indices based on frequencies of morphospecies occurrence (Morisita-Horn index) and on presence-
absence data (Sørensen's index). We suggest that our understanding of fungal diversity will be enhanced by exploring ecological
patterns underlying endophyte occurrence in host species, and discuss methods for assessing the proportion of fungal biodiversity
represented by tropical endophytes.
The scale of fungal species diversity is an open debate