Molecular methods rebuild fungal systematics

Until the end of the twentieth century, the systematics of fungi rested above all on the shape of fruiting bodies and microscopic structures, the manner of spore production and chemical reactions. Those characters are still needed, but a similar shape can arise independently in distant lineages, and close relatives can look entirely different. Sequences of ribosomal DNA and then of further genes supplied a new, comparable set of characters.

From the 1990s, molecular trees began to break up large traditional genera and to order the deep branches of the kingdom. Species known from older atlases were moved into new combinations, because a genus name should encompass a single evolutionary lineage. Later multi-gene analyses and phylogenomics reduced the errors arising from the history of a single marker, though they did not remove every uncertainty.

An important stage was the broad classification published by David Hibbett's team in 2007. The authors brought together the results of many studies and proposed names for higher groups corresponding to the phylogeny. That system too was later updated as genomes and previously omitted lineages were added. That is a feature of a working classification, not evidence of its failure.

The significance of the molecular revolution can be seen in the atlas: one species may have a modern name as well as synonyms used in the older literature. A change of label does not change the edibility of a specimen, but it improves the information about relatedness and allows characters to be compared more accurately. DNA has not replaced observation of the fruiting body; it has connected it to a testable evolutionary tree and revealed where resemblance had been misleading researchers.

1990 opens a process; it does not close a new classification

Hibbett and colleagues’ 2007 synthesis itself dates the “molecular revolution” to the early 1990s, when analyses of PCR-amplified ribosomal RNA genes began. Its result was not a single tree but a consulted classification: 195 taxa down to order, including 16 described or validated in the paper. Its most visible revisions created subkingdom Dikarya for Ascomycota plus Basidiomycota, restricted Chytridiomycota, and distributed the former “Zygomycota” among Glomeromycota and several subphyla of uncertain placement. The authors also left some genera, including Olpidium and Rozella, without assignment to higher taxa. That is an important feature of scientific reconstruction: molecular evidence can dissolve inherited groupings while explicitly retaining unresolved relationships.