A revised six-kingdom system of life

Area of Science:

• Systematics and Taxonomy
• Molecular Phylogenetics
• Microbiology
• Zoology
• Botany

Background:

• Existing classification systems require revision to incorporate new phylogenetic data.
• The need for a stable, high-level classification system that avoids excessive splitting of organisms.
• The International Codes of Nomenclature govern the naming of organisms within different kingdoms.

Purpose of the Study:

• To present a revised six-kingdom system of life, detailing classifications down to the infraphylum level.
• To integrate molecular phylogenetic evidence into the higher-level classification of life.
• To propose new groupings and phyla within eukaryotes and bacteria for a more cohesive system.

Main Methods:

• Analysis of protein sequence and molecular phylogenetic evidence.
• Application of principles of megasystematics, focusing on higher taxonomic ranks.
• Revision of existing kingdom and phylum circumscriptions based on new data.

Main Results:

• A revised six-kingdom system with five eukaryotic kingdoms (Protozoa, Animalia, Fungi, Plantae, Chromista) and one bacterial kingdom.
• Expansion of the Fungi kingdom to include Microsporidia and revision of fungal classification.
• Reorganization of Animalia into four subkingdoms and recognition of three new animal phyla (Acanthognatha, Brachiozoa, Lobopoda).
• Restructuring of Protozoa, including renaming Rhizopoda to Cercozoa and reducing protozoan phyla to 13.
• Classification of Bacteria into two subkingdoms (Unibacteria and Negibacteria) with further subdivision into infrakingdoms.

Conclusions:

• The revised six-kingdom system provides a more robust and phylogenetically informed classification of life.
• The integration of molecular data necessitates significant revisions in the higher-level taxonomy of eukaryotes and prokaryotes.
• The proposed system aims for stability and avoids an excessive number of kingdoms and phyla.