In the modern period of a more pragmatic molecular classification, the term “kingdom” appears all the time less often. Large groups of eukaryotes are referred to as “supergroups”, and often the rank of taxa is marked in the outline of the system with a fixed number of indents. The described trend of “disappearance” of kingdoms from the current eukaryotic systems has two main causes:
1. Firsts of the identified kingdoms united the multicellular organisms, i.e. animals, plants, fungi. These are widely diversified groups, divided into phyla (types, divisions) occurred on grounds different from the bases on which the phyla were distinguished by protozoologists. The phylogenetic approach forces us to reconsider the rank of the pools of multicellular animals, plants, and fungi, but tradition still does not allow mycologists, zoologists and taxonomists of higher plants to denominate the rank of types and diviisions. However, while maintaining the unshakable rank of the kingdom of the terminal branches eukaryotic phyla, we inevitably come to inflation of the clade ranks of its medial and basal parts.
2. Modern authors intuitively avoid designating ranks, since the ranking of even the taxa of the molecular cladogram has not yet been clearly formalized. The concept of rank itself refers to the taxonomic hierarchy developed during the Linnaean period. The hierarchical subordination of categories is didactically convenient and for formal logical division, which is the reason for the preservation of the "Linnean hierarchy" to this day. However, between a logical division of the "Linnean hierarchy" and the order of branching of the phylogenetic tree, revealed by molecular methods, there is no one-to-one correspondence, since the real phylogenetic tree (according to real native arbores analogy) is the result of random elimination of branches, as a result of which the structure the crown region is not strictly dichotomous. The understanding of this discrepancy by some taxonomists led them to call for the abandonment of the "Linnean hierarchy" as a whole. But such a refusal does not sufficient dissemination both for pragmatic as well as for didactic reasons. Therefore, the taxonomic community is trying to work in a situation "Linnean hierarchy" even after this hierarchy revealed its poverty.