About Species Descriptions
Many published descriptions of species are difficult to use in defining existing or new species from morphological characters for a number of reasons, most of which are unintentional. Structure consists of discrete elements within a single multinucleate cell which often are hard to visualize after the cell is crushed. Spore phenotypes also are subject to change from natural senescence or from action by a range of biotic or abiotic factors. The natural propensity for mycologists to collect and identify field-collected material just doesn’t work that well for arbuscular fungi, unless of course the healthy phenotype is well understood.
Because of some disparity between information in descriptions and that obtained from healthy specimens in collection pot cultures, INVAM has assigned a reference culture for each unique morphotype. If the morphotype can be linked confidently to a type specimen, the culture may be considered an ex-type if necessary. Otherwise, it may be linked to a description or to verification by a protologue author, in which case the accession is assigned the Latin name. A diagnoses from a reference culture then is summarized in the “species information pages” below. The format of each page is standardized for ease of comparison among species. Some species need to be synonymized (e.g., R. clarus and R. manihotis), but they still remain separate here until formal taxonomic changes occur. The exception is Ambispora leptoticha, which here is a synonymization of five separate species. Please note that not all species have a page on-line. Some of them we have never seen ourselves. Other species are listed in the table, but there are no links to a species page—they are in the works. Some species are described from voucher specimens obtained by the collection.
These pages are meant to allow the viewer to gain familiarity with important morphological characters that are relevant diagnostically for each species. Viewers who have published descriptions in their files will notice that often there may be some disparity between protologue details and those in these web pages. It is a useful exercise to examine (i) if the specimens used to classify the fungus were collected from field soils or pot cultures, (ii) date of the publication (relative to definition of new characters), and (iii) taxonomic experience and expertise of the authors. This information will provide some insights into the taxonomic problems associated with defining species. Fungal species in the species description table are ordered alphabetically rather than phylogenetically to find them easily.