Taxonomy is the practice and science of classification, or naming things. It is derived from two Greek words: taxis meaning 'order' and nomos meaning 'law' or 'science'.

Generally, the term is used when describing the classification of living organisms, but any group of related things can have their own taxonomy (e.g. rocks, cars, kitchen appliances). The 'things' that comprise the group being considered are called 'taxa' ('taxon' in singular).

In the taxonomy of living things there are various ranks of taxa. Commonly used ranks (in descending sequence from most inclusive) include: kingdom, phylum, order, family, genus and species. Ranks below species include subspecies and variety.

Much of the taxonomy of Victoria's plants and fungi is carried out by botanists at Royal Botanic Gardens (RBG) Melbourne. The National Herbarium of Victoria houses the more than one million specimens upon which this research is based. Royal Botanic Gardens Melbourne also maintains approved lists of names for Victoria's plants and fungi.

The origins of taxonomy

The Swedish scientist, Carl (or Carolus) Linnaeus is generally regarded as the originator of the system on which current taxonomy is based. His Systema Naturae published in 1735 established basic divisions within the natural world where naturally occurring things were regarded as plants, animals or minerals.

Species Plantarum, the baseline treatise on botanical nomenclature, was published by Linnaeus in 1753 and provided the foundation for modern plant and fungal taxonomy. This work outlined all the organisms known to Linnaeus with a concise description and a binomial (a two-word name) consisting of a genus name and a species name. Binomials were initially used by Linnaeus as a shorthand, but have since been adopted as the standard way to refer to all living organisms. In the binomial Banksia integrifolia, Banksia is the genus name and integrifolia is the species epithet.

In Linnaeus' eyes, species were seen as definable, unchanging entities (it was to be more than 100 years until Darwin proposed his theory of evolution). Nowadays, taxonomists often differ about where the boundaries between taxa exist. The recent advent of DNA analysis has contributed to the way that species may be defined, but there is still 'reworking' of the taxonomy of many groups of organisms.

Taxonomy at Royal Botanic Gardens Melbourne

Taxonomists at RBG Melbourne use a range of techniques for investigating the boundaries of taxa and the relationships between them (the branch of science that attempts to understand how plants are related is called systematics). Traditional taxonomy relies on comparing specimens either in the wild or in the herbarium and grouping common entities as a single taxon. This approach is still utilised but, increasingly, techniques employing DNA analysis are used to test these conventional approaches.

It is fair to say that a concise definition of a species is yet to be agreed upon by biologists. Although the conventional notion of organisms that can interbreed to produce fertile offspring remains popular, it is accepted that many plant species may hybridise to produce offspring that are capable of reproduction.

Royal Botanic Gardens Melbourne scientists publish their taxonomic findings in journals such as Muelleria and Australian Systematic Botany. Formal publication, including a Latin description or diagnosis, in a peer-reviewed journal is a prerequisite for a new species of plant or fungus to be recognised. The rules for naming plants and fungi are laid out in the International Code of Botanical Nomenclature for algae, fungi and plants.