Pseudotsuga menziesii, the Queets fir, for 70 years one of the largest known Douglas-firs [C.J. Earle].
Pseudotsuga brevifolia in habitat on the Maolan Karst, Libo County, Guizhou, China iNaturalist observation 18388661 [Mazus Jan, 2018.08.27].
This cross-section displayed at the Seaport Museum in Raymond, Washington shows how an old-growth log of Ps. menziesii harvested in the 20th Century might typically be cut to render commercial timber [C.J. Earle, 2008.07.25].
Pseudotsuga
Douglas-fir (Lipscomb 1993), Abeto de Douglas [Spanish].
The genus was first described by Carrière with the grand Douglas-fir of North America, Pseudotsuga menziesii, as the type species (it had formerly been placed in Pinus and Abies). Some 22 species and 3 varieties have been described, but many of these were discriminated by Flous (1937) on the basis of subtle distinctions in leaf anatomy and largely have not been upheld (Farjon 1990). The existence of two North American species (one with two or more infraspecific taxa) is well established. In Asia, there is a fair agreement on the number of taxa, as they are geographically and morphologically distinct; however, there is little agreement on the number of species.
Farjon (2010) finds two species, with one on Japan and one with three varieties in China, and this is the most conservative taxonomy at this time. Hermann (1982) finds seven Asian species, while Debreczy and Rácz (2011) find five, one having three varieties. There has really been only one molecular study to throw light on this problem. Wei et al. (2010) examined five cpDNA regions, two mtDNA fragments and one nuclear gene (LEAFY) in a study that considered all taxa in the genus. They found two clades, one North American and one Asian, with the North American clade resolving all three taxa (P. macrocarpa and two subspecies of P. menziesii) and the Asian clade clearly supporting P. forrestii as a good species. The cpDNA evidence placed P. japonica sister to the other Asian species, but the nuclear gene placed it sister to P. sinensis and P. sinensis var. gaussenii, and placed P. brevifolia sister to P. forrestii. The Taiwan species, P. wilsoniana, had two distinct nuclear DNA sequences, one aligned with P. brevifolia and the other with the P. gaussenii-japonica-sinensis clade, suggesting a hybrid origin for this taxon (or, I would suggest, two separate introductions of Pseudotsuga into Taiwan, first from one clade and then from the other, with subsequent introgression). Although these results are preliminary, they do suggest that P. forrestii is a good species, that it is inappropriate to treat P. brevifolia as a variety of P. sinensis, but that P. sinensis var. gaussenii is appropriately treated as a variety, and that P. wilsoniana warrants treatment as a species pending further study.
Thus this treatment presents seven species:
Molecular clock analysis shows that it has been 14.4 to 26.0 million years since the Asian and North American species shared a common ancestor, suggesting that "Pseudotsuga might have originated from North America and then migrated to eastern Asia by the Bering land bridge during the early Miocene" (Wei et al. 2010); this dating agrees with the oldest Asian fossil of Pseudotsuga, Pseudotsuga tanaii Huzioka from the early Miocene Shichiku Flora of northeast Japan (Yabe 2011). Origin in North America with Miocene dispersal to Asia via Beringia is remarkably common in the Pinaceae, also being observed in Abies section Amabilis, Picea, and Pinus subsection Strobus (Wen et al. 2016).
Evergreen trees. Bark initially smooth with transverse resin blisters, with age becoming reddish brown, thick and corky, deeply fissured into scaly ridges or flaking. Branches often pendulous, irregularly whorled; epicormic branching common on late successional trees. Short (spur) shoots absent; leaf scars transversely elliptic, slightly raised proximally but essentially flush with twig distally. Buds elongate, not or slightly resinous, apex acute. Leaves borne singly, persisting 6-8 years, alternate, short-stalked, linear, flat, green and grooved above, with 2 white stomatal bands each containing 5-8 lines of stomata beneath; 2 marginal resin ducts and 1 vascular bundle. Cones borne on year-old twigs. Pollen cones axillary, cylindric. Seed cones maturing first season, terminal on short branchlets, consisting of numerous spirally arranged scales, each scale 2-ovuled. Mature cones shed whole, deflexed or pendent from a 2-10 mm long peduncle, ellipsoid, ovoid, or cylindric, lacking apophysis and umbo; scales persistent, apex rounded; bracts ± exserted, apex 3-lobed with the middle lobe long and narrow. Seeds winged; cotyledons 2-12. x=12, 13 (Lipscomb 1993, Li 1975, and pers. obs.).
Canada, China, Japan, Mexico, Taiwan, Tibet, United States, and Viet Nam, in subtropical to cool-temperate forest.
Native distribution of Pseudotsuga; click on icons for species identification. Distribution data from GBIF, 2021.02.22.
The largest, tallest, and oldest trees are in P. menziesii subsp. menziesii.
See the species accounts.
P. menziesii is one of commonest trees in western North America, an agroforestry species and invasive weed in New Zealand, a common ornamental and agroforestry species in Europe, and easily found in most of the rest of the world's temperate climate zones. The other species are of relatively limited occurrence, are seldom used as ornamentals, and are typically seen only in the largest arboreta.
The genus name is derived from the Greek pseudo, false, and the Japanese tsuga, hemlock (Lipscomb 1993).
Farjon, Aljos. 1990. Pinaceae: drawings and descriptions of the genera Abies, Cedrus, Pseudolarix, Keteleeria, Nothotsuga, Tsuga, Cathaya, Pseudotsuga, Larix and Picea. Königstein: Koeltz Scientific Books.
Flous, F. 1937. Révision du genre Pseudotsuga. Bull. Soc. Hist. Nat. Toulouse 71: 33-164.
Hermann, R. K. 1982. The genus Pseudotsuga: historical records and nomenclature. Special Publication 2a, Forest Research Laboratory, Oregon State University, Corvallis. 34pp.
Wei, X.-X., Z.-Y. Yang, Y. Li, and X.-Q. Wang. 2010. Molecular phylogeny and biogeography of Pseudotsuga (Pinaceae): insights into the floristic relationship between Taiwan and its adjacent areas. Molecular Phylogenetics and Evolution 55:776–785.
Wen, J., Z.-L. Nie, and S. M. Ickert‐Bond. 2016. Intercontinental disjunctions between eastern Asia and western North America in vascular plants highlight the biogeographic importance of the Bering land bridge from late Cretaceous to Neogene. Journal of Systematics and Evolution 54:469–490.
Yabe, A. 2011. Pseudotsuga tanaii Huzioka from the earliest Miocene Shichiku Flora of northeast Japan: Systematics and ecological conditions. Paleontological Research 15:1–11.
Little, E.L. Jr. 1952. The genus Pseudotsuga (Douglas-fir) in North America. Leafl. W. Bot. 6: 181-198.
Last Modified 2024-12-12
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