Some Problems in Fungus Phylogeny

Abstract

Owing to the nature of fungi their fossil remains are mostly limited to hyphae in fossilized wood and to the remains of pycnidia or perithecia in leaves or stems, with a few records of woody sporophores of polypores. These do not reveal much that is of help in phylogenetic studies, except to show us that higher fungi existed as parasites and saprophytes millions of years ago. Failing palaeontological records recourse must then be had to the other resources of the phylogeneticist: comparative morphology and ontogeny, and serum diagnostic studies. Comparison of the morphology of now existing species is useful on the theory that evolution may result in divergences so that the more nearly related species will be those with the greatest similarities and, conversely, those that are less similar will represent greater evolutionary modifications and hence more distant relationship. This is probably true in the main, but there are many opportunities for error. It must be borne in mind that sometimes a single gene difference may produce a very great effect. Some dwarf plants, e.g. the Cupid sweet pea, appear to have arisen from large plants by this method and yet the difference is so striking that we would be inclined to consider the organisms as quite distantly related. So we may, on the basis of comparative morphology, erect a scheme of ascent or descent in which because of some