(proposed)
Taxus calcicola
None are known, but traditionally plants of this species have likely been referred to by vernacular names for other yews of Yunnan, Guizhou, and northern Vietnam.
Type: China, Yunnan, Hekou County, Nanxi town, Longyincong, 1000 m, 22.68333°N, 104.01667°E, 2006.09.20, L.M. Gao & M. Moeller GLM-06239 (Holo KUN, Iso E). Both Taxus chinensis and T. mairei occur within the range of T. calcicola and herbaria likely contain many specimens collected on carbonate substrates and assigned to those taxa, that merit identification as T. calicola. The species was described as an outcome of an extensive molecular and morphological study that considered samples from 79 populations of Taxus wallichiana (sensu latu) across the entire distribution range of the species, and found those samples represented 5 distinct population clusters. Four of the clusters mapped onto the known species T. wallichiana (sensu strictu), T. chinensis, T. mairei, and T. florinii; the fifth cluster mapped onto a new grouping, which the authors assigned to T. calcicola (Möller et al. 2013).
Trees to 20 cm dbh and 10 m tall, typically with a single trunk. Bark not described. Twigs irregularly alternate, slender, round, finely grooved beside decurrent leaf bases, green turning yellowish green to ochre or bronze. Foliage buds ovoid with persistent, abaxially keeled basal scales. Leaves spirally inserted, nearly sessile, base twisted, appearing distichous, spreading at nearly right angles, densely arranged on twigs, 14-23 × 2.6-3.5 mm, linear, slender, straight, upper parts almost as broad as the lower parts, thick and coriaceous, margin ± revolute, lustrous dark green above, yellowish green with two pale yellowish green stomatal bands 0.7–1.2 mm wide below, apex abruptly pointed and mucronate. Midrib on the adaxial (upper) side raised in fresh leaves, 0.2 mm wide, continuous to apex, on the abaxial side elevated, 0.4–0.6 mm wide and continuous to the apex. Pollen cones axillary, solitary, forming rows on both sides of fertile shoots, ovoid, yellowish green to pale brown, with basal bracts. Seed cones axillary, solitary, sessile, with minute triangular scales covering a very small dwarf shoot and the single terminal ovule except the micropyle. Seeds ovoid, ca. 5.2–6.5 × 4.0–5.0 mm, slightly compressed, with slightly obtuse lateral ridges in upper parts, apex obtuse and with a mucro, dark brown, enclosed in a cup-shaped, red succulent aril, with the apical mucro subequalling or slightly protruding from the aril; hilum ellipsoid (Möller et al. 2013).
Taxus calicola has straight leaves with parallel margins, an acute apex, and a low leaf length/width ratio of (4.11-)5.82(-8.12). T. mairei, in contrast, has sigmoid leaves with margins not parallel in the distal 1/4 of the leaf; its apex is acuminate and the leaf length/width ratio is (5.21-)7.75(-11.55). T. chinensis differs in having a densely papillate midrib and a matte surface on the lower leaf (Möller et al. 2013).
China: southeast Yunnan, northeast and southwest Guizhou; northern Vietnam: Laocai, Son La, Hoa Binh and Ha Giang. Occurs at elevations of 810 to 1525 m on karst limestone hills in broadleaf evergreen and mixed angiosperm/conifer forests. Common associates include angiosperm trees such as Clausena excavata Burm. f., Cleidion bracteosum Gagnep., Eurya groffii Merr., Litsea cubeba (Lour.) Pers., Pavieasia anamensis Pierre, Sinosideroxylon pedunculatum (Hemsl.) H. Chuang, Xantolis boniana (Dubard) P. Royen, and Yunnanopilia longistaminea (W.Z. Li) C.Y. Wu & D.Z. Li. Associated conifers include Amentotaxus yunnanensis, Cephalotaxus mannii, and members of the Podocarpus neriifolius species complex (Möller et al. 2013).
The IUCN has not prepared a conservation assessment for this species, but Möller et al. (2013) propose that it should be classified as "Endangered" because, although the species has a fairly large extent of occurrence at ca. 35,000 km², the plants grow only in small and isolated patches of forest in very low densities, with a total number of individuals estimated to be less than 2000. None of the known localities are in protected areas and all are subject to habitat degradation associated with nearby forest clearance that alters the microclimate of the limestone karst habitat.
No data as of 2023.02.23.
No data as of 2023.02.23.
A list of specimens is presented by Möller et al. (2013).
The epithet calciola refers to the species' association with carbonate substrates, especially karst (Möller et al. 2013).
Moeller, M., L. M. Gao, R. R. Mill, J. Liu, D. Q. Zhang, R. C. Poudel, and D. Z. Li. 2013. A multidisciplinary approach reveals hidden taxonomic diversity in the morphologically challenging Taxus wallichiana complex. Taxon 62(6):1161-1177.
The species account at Threatened Conifers of the World, which also includes photographs.
Last Modified 2023-02-26
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