Abstract:
Fungi are believed to be diverse in the tropics, but because many groups are
only known from their DNA sequences this hampers comparative diversity studies. We
investigated mycorrhizal Sebacinales (Basidiomycota) of 67 individuals of Ericaceae and
Orchidaceae in a tropical mountain ecosystem in Southern Ecuador to provide a ?rst
estimate of whether these fungi are particularly diverse in the Northern Andes. We par-
tially sequenced the internal transcribed spacer (ITS) and large subunit (LSU) regions of
the nuclear ribosomal DNA and analyzed them together with all Sebacinales sequences
available from GenBank. The clustering optimization technique was used to determine
clustering parameters that maximize the comparability between molecular operational
taxonomic units (MOTUs) obtained from the distinct loci. Sampling effort and species
richness were estimated with rarefaction-accumulation curves and non-parametric esti-
mation using Chao2 and compared between Southern Ecuador and France. Clustering
optimization indicated that a 1% LSU distance threshold corresponds to the commonly
used 3% dissimilarity threshold for ITS, and that a clustering algorithm close to single-
linkage clustering is optimal. The resulting clusters show that about 8?9% of observed Sebacinales MOTUs occur in the study area and that most of these MOTUs are endemic
(74%). The widespread MOTUs from Southern Ecuador were also found in Panama, North
America and Europe. The estimation of species richness revealed unsaturated sampling of
Sebacinales in general and also in our study area. Our results suggest a high diversity of
Sebacinales associated with Ericaceae and Orchidaceae at the study site in Southern
Ecuador, but no hotspot of Sebacinales in comparison with other areas.
