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According to the Code, " for any taxon below the rank of genus, the
correct name is the combination of the final epithet of the earliest
legitimate name of the taxon in the same rank, with the correct name
of the genus or species to which it is assigned" (Article 11.4).
Therefore, the correct species name should be assigned based not only
on the priority, but also on the legitimate name of the genus to
which it belongs. Then, there comes the question: which is the
legitimate species name: Aegilops tauschii or Triticum
tauschii? The answer is: Both.
From objective reality, there are only two absolute units of living
organisms: individuals and species. A species is a group of
individuals which connect to each other as a unit by their
indispensable relationships of breeding. There is no absolute
boundary among genera, families and the taxa above. Taxonomic
treatment above species cannot avoid arbitrariness. It is not
surprised that many genus combinations have been proposed. When
Cosson (1849) published the species name for the D-genome diploid, he
put it in the genus Aegilops, and Aegilops is a
legitimate genus. Hence, Aegilops tauschii should be the
legitimate name if classification of the genus Aegilops is
followed. On the other hand, Triticum is also a legitimate
genus name. The argument is how to define the genus Triticum.
Correct taxonomic nomenclature is very important in plant
sciences. Mis-identifying a taxon may cause unnecessary waste of the
precious time and resources of other scientists. For instance, Jensen
et al. (1986) and Jensen (1990) and Yang et al. (1990) worked on an
accession, PI 314623. This material was collected in 1967 by USDA-ARS
plant explorers Drs. Q. Jones and W. Keller in a mountainous area
about 180 km east of Alma Ata, Kazakhstan and mis-named as
"Agropyron batalinii". When the plants of PI 314623 were
compared with the type specimens (it was designated as Triticum
batalinii Krassn. by the Russian scientist) in herbarium of
Komarov Botanical Institute (LE), St. Pertersburg, Russia, they were
found to be quite different from the type specimens, but similar to
another type specimen named Roegneria carinata Ovcz. et Sidor.
The mistake made by Jones and Keller caused Jensen et al. (1986) and
Jensen (1990) made the wrong conclusion about the genome constitution
of "batalinii", which they worked on, and led Yang et al. (1990) to
wrongly identified taxon "nana" as an independent species,
though it should only be a variety of Kengyilia batalinii
(Krassn.) Yang, Yen et Baum (Yen et al. 1996). Recently, J.
Dvorak and M.C. Luo conducted RFLP analysis of Aegilops tauschii
Cosson from China. They were astonished to observe a distinctive
band shown in some accessions they analyzed. Based on this
observation, they classified these accessions as a new group of this
species. After they checked these materials again, they found these
materials were actually Ae. cylindrica Host. but misclassified
to Ae. tauschii Cosson in Crop Germplasm Institute of
Chinese Academy of Agricultural Sciences. Therefore, plant scientists
are urged to use the correct, legitimate scientific name to call the
plant material they work with.
In conclusion, both Aegilops tauschii Cosson and Triticum
tauschii (Cosson) Schmalh. are both valid scientific names for
the D-genome diploid Triticeae species in accordance with the Rules
of the Code. The name Ae. squarrosa L., if it applied
to the D-genome diploid species, is not a legitimate name in
accordance with the Article 7.4 of the Code, because Linne (1753)
described it on the basis of a type specimen that was actually a form
of Ae. triuncialis L. Trying to make Aegilops
squarrosa a legitimate name, Zeven and Zhukovsky (1975) offered a
compromising proposal: assigning Ae. squarrosa auct.
non L. to the D-genome diploid. However, this name is also not
legitimate according to Article 11.4 of the Code, because the
earliest legitimate name of this taxon is Ae. tauschii Cosson
which was assigned in a valid publication and determined by means of
nomenclature type.
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