Introducing

Taxonomy

Names and naming

Names are the currency of taxonomy.

The scientific name given to a species or other taxon is the index around which a great deal of information is stored, organised, and can be retrieved. Names are like the card catalogue in the library of life.

For this reason, taxonomists take names very seriously (at times, perhaps, to the point of obsession). For this reason also, the scientific naming of organisms is carefully controlled, although not in the way that many people imagine.

Two Eastern Grey Kangaroos (Macropus giganteus). The scientific name is always in Latin, with a genus followed by a species name. Macropus is from the Latin for 'large foot', giganteus from the Latin for 'very large'. Closely related species of kangaroos and wallabies will share the Macropus genus name, but only this species can be called Macropus giganteus.

 

Many aspects of the naming of organisms are controlled by agreed sets of international rules, the Codes of Nomenclature. One Code covers the naming of algae, fungi and plants, another covers the naming of animals, while others cover the naming of bacteria and their relatives, viruses, and cultivated plants.

It may seem odd that there are separate Codes covering different groups of organisms; indeed, there have been attempts to combine the various Codes into a universal Code covering the naming of all living organisms. However, in the decades and centuries during which naming conventions have developed, the Codes have diverged quite a lot, and attempts to create a universally accepted Biocode have so far not been acceptable to all taxonomists.

The Codes of Nomenclature establish rules around what taxonomists need to do in order to publish names that will be regarded as nomenclaturally correct. For example, every name must be permanently associated with a specimen or other voucher, names must be published in a way that is accessible to other taxonomists (usually by publishing in a peer-reviewed scientific journal), and the earliest validly published name for a species or other taxon is (with a few exceptions) deemed the correct one.

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The type specimen of the bryozoan ('moss animal') Craspedozoum spicatum. Type specimens are especially important in taxonomy, as they permanently fix the meaning of a name. In this case the type specimen is a carefully preserved microscope slide. For a plant species the type specimen will usually be a pressed specimen mounted on a sheet; for a bird it will usually be a skin; for a fish it will usually be a specimen preserved in alcohol.

Importantly, if taxonomists follow the rules established in the relevant Code, they are free to name species and other taxa with no other restrictions. There are no committees that decide what can be named or by whom, or that control 'allowable' or 'disallowed' taxonomies.

This is because taxa are scientific hypotheses. When a taxonomist names a species, they are in essence erecting a hypothesis that the species in question is real and has valid meaning in nature. And like any science, taxonomists must be free to hypothesise without restriction for the science of taxonomy to be robust and healthy.

Of course, other taxonomists (indeed, anyone) may accept or reject a taxonomist's hypotheses. Over time, species that are well-founded and hence are useful and meaningful to others will be accepted by a majority of taxonomists and other scientists, while species that are poorly founded will be rejected and will fall out of use.

An often-heard complaint about taxonomists is that they 'keep changing the names of things'. It's true that names do on occasion need to change. There are two main reasons for this.

For much of its history in Australia, the scientific name for the cane toad was Bufo marinus. However, recent taxonomic research has shown that the large genus Bufo is best regarded as comprising several distinct genera. Because of this growth in our knowledge, the cane toad has been renamed Rhinella marina. While inconvenient for a while, such name changes are important to ensure that the names of organisms reflect the most recent taxonomic knowledge of their evolutionary relationships.


Firstly, one of the foundational rules of nomenclature in all the Codes is that the first valid name for a species is the correct one. Sometimes this leads to a name being changed when a previously obscure but valid earlier name is found. Luckily, this happens relatively infrequently, and there are provisions for reducing its impact for familiar names or cases where the impact of the name change would be large.

A more important reason for changing the names of species is the discovery of new knowledge about their relationships. One aspect of the modern system of naming established by Linnaeus in the 18th Century is a 'double-edged sword'. This is the requirement that every species have a double name (a binomial), comprising a genus name followed by a species name.

 

This convention is extremely useful in many respects. It means that some key information about relationships is captured in the name itself. This helps us remember, for example, that all species of kangaroos and wallabies in the genus Macropus are closely related, and that the black or swamp wallaby (Wallabia bicolor) is more distant (because it's in a different genus).

The downside is that if research indicates that a species must be moved from one genus to another, then its name must necessarily change to reflect its new position. While this may be regarded by some as unfortunate, it's important to remember that it reflects growth in knowledge of the relationships of species.

Indeed, a recent analysis using very sophisticated methods indicates that the swamp wallaby should be moved into the same genus as the kangaroos and other wallabies. If this becomes generally accepted by taxonomists, its name will change from Wallabia bicolor to Macropus bicolor.

 

The most useful taxonomy is one that accurately reflects evolutionary relationships; while this sometimes means names need to change, a static taxonomy that did not grow as understanding grows would not serve the needs of the many users of taxonomy very well.

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