The recent study of Willyard et
al (2017) on lineages of Ponderosa Pine (Pinus
ponderosa) is important and at the same time highly problematic. The study strongly demonstrates that Pinus ponderosa is a complex lineage
containing several distinct taxa which merit taxonomic treatment.
Willyard et al (2017) suggest treatment
of the taxa in the lineage as full species:
Pinus ponderosa, P. benthamiana,
P. scophulorum and P. brachyptera.
This will not find wide acceptance in the
non-botanical world of commerce. A long
history of practical use, common understanding, and governmental inertia will result
in default back to a broadly circumscribed, single species model. Unfortunately, the single taxon model fails
to account for geographic and evolutionary distinct units within this clade,
and is not a scientifically supported, proper classification. Put crudely, the guy at the lumber yard is not going to care...!
The principal purpose of any
classification is utility. Treatment of
the taxa of the Pinus ponderosa
lineage as subspecies would have a much higher probability of gaining wide
application. Without reference to
geography, the identification of individual trees is not easy, even with mature
cones and bud-color features at hand, because the overall morphogical
similarity between the individual taxa is substantial (Callaham 2013). Users of a classification which employs
infrataxa can refer only to Pinus
ponderosa generally in instances where their determination of subspecies is
unimportant (i.e. this timber is ponderosa pine) or in geographic areas where
the taxa overlap (i.e. in the KR-CaRH region of California, where both P. ponderosa and P. benthamiana haplotypes are present).
The five validly published taxa treated as subspecies are:
Pinus ponderosa P. Lawson & C. Lawson
ssp. ponderosa, Agric. Man. 354
(-355). 1836
P. ponderosa ssp. ssp. benthamiana (Hartw.) Silba -- J. Int. Conifer
Preserv. Soc. 16(1): 30. 2009
P. ponderosa ssp. brachyptera (Engelm.) Silba -- J. Int. Conifer Preserv. Soc.
18(1): 16. 2011.
P. ponderosa
ssp. scopulorum (Engelm.) A. E. Murray
-- Kalmia 12: 23. 1982
P. ponderosa
ssp. washoensis (H. Mason &
Stockw.) A. E. Murray, Kalmia 12: 23. 1982.
The treatment of the taxa of Pinus ponderosa as subspecies is
consistent with broad practice for many higher plants. Treatment of the clade as varieties (where
not all of the required names are valid) is not consistent with treatment
models which have survived the test of time (Simpson 1945, Clausen 1951 Dobzhansky
1951, Stebbins 1966, Mayr 1982) and is inconsistent with common practice in the
larger portions as applied to higher plants (Briggs & Walters 1971) worldwide.
In plant taxonomy, my opinion is that we devalue the worth of our effort when we do not defer to the practical needs of society at large whom consume our names.
The five ponderosa pines are subspecies.
References:
Briggs, D., & S. M. Walters. 1971
Plant Variation and Evolution. White & Gilbert, U.K.
Callaham , R. Z. 2013 . Pinus
ponderosa : Geographic races and subspecies based on morphological variation.
USDA Forest Service, Pacific Southwest Research Station PSW-RP-265. Washington,
D.C.
Clausen J. 1961.
Stages in the evolution of plant species. Cornell Univ. Press, Ithaca, N.Y.
Dobzhansky, T. 1951.
Genetics and the origin of species.
Columbia Univ. Press, New York, N.Y.
Mayr, E. 1982. Growth of Biological Thought: Diversity, Evolution,
and Inheritance. Harvard Univ. Press Cambridge, M.A.
Simpson, G. G. 1945. The
Principles of Classification and a Classification of Mammals. Bull. American
Museum Nat. Hist. 85: 1-23.
Stebbins, G. L. 1966. Processes of organic evolution. Prentice Hall, Engelwood Cliffs, N.J.
Willyard, A. W. et al. 2017. Pinus
ponderosa: A checkered past obscured four species. Amer. J. Bot. 104(1):1-21.
