Taxonomy versus evolution

Four major taxonomical issues are commented briefly in view of evolutionary biology: classification, hierarchy, trees and nomenclature. It is argued that distinction between diachronous and synchronous classification schemes is of primary importance in taxonomy. The currently adopted classification of life is meant to be diachronous and Linnaean at the same time. This is problematic, because morphological and genetic gaps between higher taxa are the result of evolution; they are apparent only at a horizontal cross section of the phylogenetic tree and cannot be observed in time along the spatio­temporal continuum of populations. On the other hand, synchronous classifications would be consistent with the sharp boundaries necessary to set up a meaningful Linnaean hierarchy. Distinguishing Darwinian phylogenetic trees from Hennigian cladograms is just as well important. Monophyly­paraphyly­polyphyly concern the status of a group in a diachronous classification with respect to the phylogenetic tree, while cladograms can be logically contrasted with synchronous classifications. This necessitates introduction of new terms, monoclady, paraclady and polyclady, all referring to the respective conditions of groups of organisms in a cladogram. The existence of different and independent nomenclatural codes conserves an exceedingly obsolete view on the living world—harmonization of the codes with one another as well as with evolutionary theory is inevitable.