Acyclic polyols and higher taxa of fungi

RAST, D. M. & PFYFFER, G. E., 1989. Acyclic polyols and higher taxa of fungi. Acyclic polyols (sugar alcohols), widely distributed within the fungi, are the fungal secondary metabolites (in the sense of non-ubiquitous constituents) studied most extensively and appear to be physiologically important. An account is given of the systematic distribution of polyols within the Eumycota, and the influence of (1) the carbohydrate nutrient source, (2) the stage of development and (3) the growth form on the polyol pattern in fungi, to obtain additional insights into species constancy is considered. Delimitation of groups based on polyol characters (P, three states: P_0, polyols absent; P_1, polyols, except mannitol, present; P₂, mannitol (and other polyols) present) yields chemotaxa that coincide with Oomycetes (P_0,.), Zygo-and Hemiascomycetes (P₁), and an assemblage of taxa that consists of Chytridiomycetes, Euascomycetes, Basidiomycotina and Deuteromycotina (all P₂) with the conspicuous exception of some of the imperfect yeasts (P₁). Hence, polyol characters appear to be extremely conservative and, therefore, lend themselves to use as markers for the assignment to conventional taxa of species with doubtful systematic affinity. Considering other biochemical features, as well as the model-testing of the classification systems followed in Ainsworth & Bisby's Dictionary of the Fungi (6th and 7th editions) with the P-macrochemotaxa established here, recommendations are made to change the rank of some higher taxa, so as to render them homogeneous with respect to the P_0,., P₁ and P₂ character states. The proposals relate to Mastigomycotina, Blastomyceles and Endomycetales and are, in principle, realized already in some other classification systems.