ABSTRACT

This chapter introduces the argument that the persistent furor over species is based on real biology and real differences among organisms. The units traditionally called species in different groups of organisms are different kinds of things; there is no way to fix this and make the species rank comparable across life. The author and colleagues in the past attempted to define a phylogenetic species concept, but the lack of common criteria to distinguish the species rank from other levels became clear. Species and other taxonomic ranks like genera are not comparable between groups, however, clades are. All named taxa should be hypothesized clades, and rankless phylogenetic taxonomy in the PhyloCode style needs to be extended to the former species level. Biodiversity is not just species; it is the entire hierarchy of nested clades representing phylogenetic relationships among all organisms, together with their genetic and functional characteristics, spatial distributions, and ecological relationships.