BOT300 Home Page

Nomenclatural principle II - the type method (25-Feb-03)

Principle II

"The application of names of taxonomic groups is determined by means
  of nomenclatural types."



Sample nomenclatural problem (devised, like those on today's handout, by Prof. J. E. Eckenwalder; commentary on answers by NT and TAD)

The "Willow of Babylon" mentioned in Old Testament accounts was probably a species of poplar, Populus euphratica Oliv., that spans the Old World Tethyan arid zone from Spain and Morocco all the way to China. It, and its closest relatives are such unusual species that they have sometimes been placed in a genus distinct from the cottonwoods, aspens, and other poplars with which we are more familiar. The varied taxonomic treatments that have been applied to these strange trees result in a varied nomenclature.

The following taxa have been described and associated with the corresponding types:

Populus L., 1753

(type: P. alba L.)

Balsamiflua Griff., 1848

(type: B. deltoides Griff.)

Populus L. sect. Turanga Bunge, 1851

(type: P. euphratica Oliv.)

Turanga Kimura, 1938

(type: P. euphratica Oliv.)

Tsavo Jarmol., 1949

(type: Celtis ilicifolia Engler)

Populus alba L., 1753

(type: specimen 'A')

Populus deltoides Marsh., 1785

(type: specimen 'B')

Populus euphratica Oliv., 1807

(type: specimen 'C')

Balsamiflua deltoides Griff., 1854

(type: specimen 'D')

Celtis ilicifolia Engler, 1895

(type: specimen 'E')

Populus euphratica Oliv. subsp. denhardtiorum Engler, 1898

(type: specimen 'F')

In addition, the following relevant combinations have been published:

Solve the following problems:

But first, some "-nyms" and other words to get started:

1) 'A' and 'B' represent distinct species of typical poplars, while 'C' to 'F belong to the Willow of Babylon group. If these two groups represent different sections of the same genus, what are the correct sectional names?



'A' Populus alba L., 1753

Populus § Populus

§Populus is an autonym, a tautonym for the generic name created automatically when §Turanga was described.

'B' Populus deltoides Marsh., 1785


'C' Populus euphratica Oliv., 1807

Populus § Turanga Bunge

The type of the new section is P. euphratica Oliv., 1807.

'D' Balsamiflua deltoides Griff., 1854

'E' Celtis ilicifolia Engler, 1895

'F' Populus euphratica Oliv. subsp. denhardtiorum Engler, 1898

2) If 'D' represents a distinct species of the same genus as 'A' and 'B', what is its correct name?

P. 'your choice' 'Student'

- because Griffith's "deltoides" was described under his new genus Balsamiflua and is not the same thing as Marshall's "deltoides." Since P. deltoides Marsh. has priority, Griffith's species is a homonym (in other words, one of two identical epithets that are based on different types, of which only one can be legitimate). For this reason Griffith's species needs a new name.

3) If 'D' belongs to the same species as 'C', and 'E' and 'F' represent another species, what are the correct names of these two species?



'C' Populus euphratica Oliv., 1807

P. euphratica Oliver

This name has priority

'D' Balsamiflua deltoides Griff., 1854


'E' Celtis ilicifolia Engler, 1895

P. ilicifolia (Engler) Rouleau

P. euphratica can't be used here because that is a different species. Celtis ilicifolia would need to be transferred to Populus, and that is what Rouleau has done.

'F' Populus euphratica Oliv. subsp. denhardtiorum Engler, 1898

4) If 'E' and 'F' represent a species of a genus different from that of all other specimens (but not Celtis, which was simply a mistaken identification), what is the correct name of the species?



'E' Celtis ilicifolia Engler, 1895

Tsavo ilicifolia (Engler) Jarmolenko

Engler's C. ilicifolia is the type of Jarmolenko's new genus.

'F' Populus euphratica Oliv. subsp. denhardtiorum Engler, 1898

The genus Turanga (Turanga ilicifolia (Engler) Kimura) cannot be used because we are no longer including the type of Turanga (P. euphratica Oliv.) in the genus with 'E' and 'F'.

5) If 'C' and 'D' also belong to the same genus as 'E' and 'F', which is different from the genus of 'A', and if each pair of specimens represents a subspecies of a single species, what are the correct subspecies names?

Balsamiflua, the genus for these four specimens, is determined by priority.



'C' Populus euphratica Oliv., 1807

Balsamiflua euphratica (Oliver) Kimura

ssp. euphratica

An autonym; B. deltoides is the type of Griffith's genus Balsamiflua, but Oliver's epithet has priority.

'D' Balsamiflua deltoides Griff., 1854


'E' Celtis ilicifolia Engler, 1895

Balsamiflua euphratica (Oliver) Kimura

ssp. denhardtiorum (Engler) 'Student'

'F' Populus euphratica Oliv.

subsp. denhardtiorum Engler, 1898

The subspecific epithet does have priority as a subspecies. As Nadia pointed out to the class, in P. denhardtiorum (Engler) Dode it was not absolutely required to use Engler's epithet in the new species combination, but it helps enormously (it's "polite") if people do that, as Dode did. Keep this in mind when you come to the Acer problem set.

6) If we return to the idea that 'D' represents a distinct species, but decide that it belongs in a genus together with 'B' that is distinct from the genus of all the other specimens, what are the correct names of the two species containing 'B' and 'D'?


'B' Populus deltoides Marsh., 1785

Balsamiflua 'your choice' (Griffith) 'Student'

Marshall's species is now a homonym.

'D' Balsamiflua deltoides Griff., 1854

Balsamiflua deltoides Griffith

The type of Balsamiflua Griffith, the first genus available since Populus no longer includes these species.

James L. Reveal - Lecture Notes

Summary Comments on the International Code of Botanical Nomenclature

Remember the Kew Rule?

Click HERE for Nadia's explanation...

[Back to TOP] 


Greuter, W. et al. (2000). International Code of Botanical Nomenclature (St. Louis Code) adopted by the Sixteenth International Botanical Congress St Louis, Missouri, July-August 1999. Electronic version of the original English text. [The printed and only official version of the Code has been published as International Code of Botanical Nomenclature (St Louis Code). Regnum Vegetabile 131. Koeltz Scientific Books, Kšnigstein. ISBN 3-904144-22-7]

Radford, A. E., Dickison, W. C., Massey, J. R. & C. R. Bell (1974). Vascular Plant Systematics. New York, Harper & Row. [Chapters 3, 4]

Lawrence, G. H. M. (1951). Taxonomy of vascular plants. New York, Macmillan.

Porter, C. L. (1967). Taxonomy of flowering plants. San Francisco, W. H. Freeman.

|BOT300S Home Page | U of T Botany | University of Toronto |

© 2003 Botany Department, University of Toronto.

Please send your comments to; last updated 2-Mar-2003