**1. Genus Overview:**
– Etymology: Term ‘genus’ originates from Latin ‘genus,’ related to ‘gignere’ (to bear; to give birth to).
– Founders: Carl Linnaeus popularized ‘genus’ in ‘Species Plantarum’; Joseph Pitton de Tournefort founded modern genera concepts.
– Role: Essential in taxonomy for distinguishing organisms.
– Nomenclature: Scientific name is generic, capitalized, and combined with species name.
– Type Concept: Each genus has a designated type species in zoology.
– Categories: Zoology classifies names as available/unavailable based on nomenclature codes.
– Homonyms: Names with multiple meanings discouraged by nomenclature codes.
– Higher Classifications: Type genus forms basis for higher taxonomic ranks.
**2. Genus Naming Conventions:**
– Rules: International Code of Zoological Nomenclature governs naming.
– Codes: Melbourne Code for algae, fungi, plants; IRMNG for marine/nonmarine genera.
– Registers: WoRMS for marine species; IRMNG for generic homonyms.
**3. Genus Statistics:**
– Accepted Genera: Approx. 310,000 out of c. 520,000 published names.
– Kingdom Estimates: Animalia, Plantae, Fungi, Chromista, Protozoa, Bacteria, Archaea, Viruses.
– Registers: Official registers for viruses, prokaryotes, compendia for other groups.
– Genus Size: Varies significantly among taxonomic groups; debates on maintaining large genera.
**4. Taxonomic Classification Ranks:**
– Ranks: Domain, kingdom, phylum, class, order, family, genus, species.
– Additional Ranks: Subphylum, subclass, subfamily, tribe, superphylum, infratribe.
– Purpose: Organize organisms based on evolutionary relationships.
**5. Taxonomic Publications and Resources:**
– Index Fungorum: Lists fungal names.
– Algaebase: Information on algae species.
– LPSN: Catalogs prokaryotic names.
– Index Nominum Genericorum: Compiles botanical generic names.
– Catalogue of Life: Annual species checklist.
Genus (/ˈdʒiːnəs/ pl.: genera /ˈdʒɛnərə/) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.
- E.g. Panthera leo (lion) and Panthera onca (jaguar) are two species within the genus Panthera. Panthera is a genus within the family Felidae.
The composition of a genus is determined by taxonomists. The standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera. There are some general practices used, however, including the idea that a newly defined genus should fulfill these three criteria to be descriptively useful:
- monophyly – all descendants of an ancestral taxon are grouped together (i.e. phylogenetic analysis should clearly demonstrate both monophyly and validity as a separate lineage).
- reasonable compactness – a genus should not be expanded needlessly.
- distinctness – with respect to evolutionarily relevant criteria, i.e. ecology, morphology, or biogeography; DNA sequences are a consequence rather than a condition of diverging evolutionary lineages except in cases where they directly inhibit gene flow (e.g. postzygotic barriers).
Moreover, genera should be composed of phylogenetic units of the same kind as other (analogous) genera.