Introducing DOTUR, a computer program for defining operational taxonomic units and estimating species richness. DOTUR is a freely available computer program that uses a distance matrix to assign sequences to operational taxonomic units (OTUs) using either the nearest, average, or furthest neighbor clustering algorithms for all possible distances and then constructs rarefaction and collector’s curves for a variety of ecological parameters [30]. These curves can be used to compare the relative richness, the number of different OTUs in a community, of two samples and to estimate the overall richness within a sample.