Tautonymy
Tautonymy in nomenclature refers to the genus name and species epithet having exactly the same spelling.
Examples
- Natrix natrix (Linnaeus, 1758)
- Larix larix (L.) H. Karsten
The first, a snake, is ruled by the International Code of Zoological Nomenclature for animals, where this is allowed.
The second, a published name for the European Larch, is ruled by the International Code of Botanical Nomenclature for plants, where tautonymy is not allowed. If a species (in this example, originally Pinus larix L.) is transferred to another genus (here, to the new genus Larix), and this move creates a tautonym, one must find the next earliest validly published name, or propose a new name (in this case Larix decidua Miller).
It is allowed for the genus and species of a plant to mean the same, without being identical in spelling. For instance, Arctostaphylos uva-ursi means bearberry, in Greek and Latin respectively. There are also a few instances of modification of the genus name in the species, such as the fern Polypodium polypodioides, which means "a polypodium that is like a polypodium". Differences as small as a single letter are permissible, as in the Jujube shrub, Ziziphus zizyphus.