Didymodon anserinocapitatus (Musci, Pottiaceae) New to the New World

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The moss Didymodon anserinocapitatus, previously known only from eastern China, is reported from the foothills of the Rocky Mountains in Colorado and New Mexico. Study of the genus Didymodon Hedw. in North America uncovered a distinctive species new to the flora: DIDYMODON ANSERINOCAPITATUS (X.-j. Li) Zand., Bull. Buffalo Soc. Nat. Sci. 32: 162. 1993. Barbula anserinocapitata X.-j. Li, Acta Bot. Yunnan. 3: 103. 1981. Plants green to reddish green. Stems to 1.5 cm long, central strand present, strong, sclerodermis distinct, hyalodermis absent, axillary hairs 3-4 cells long, the basal-most thicker-walled. Stem leaves erect-appressed when dry, spreading when moist, monomorphic, lanceolate, adaxially weakly concave across leaf, 0.7-1.1 mm long without tip, to 2.2 mm long whole, base short-sheathing to long-ovate or scarcely differentiated in shape, margins recurved at midleaf, entire, apex abruptly thickened, long-elliptic to ovate, of many thickwalled cells, usually soon deciduous, absent in mature leaves; costa excurrent, little widened or tapering at midleaf but swollen in excurrency, adaxial costal cells quadrate, 4-6 cells wide at midleaf, epidermis present on both sides, guide cells in 2 layers, dorsal stereid band weak, ventral absent or weak, hydroid strand sometimes present; basal laminal cells differentiated medially, walls thin; upper laminal cells 8-10 pIm wide, 1:1, papillae essentially absent, lumens angular, walls thin, weakly convex on both sides, unistratose except in deciduous apex; basal cells quadrate to rectangular. Sexual features and sporophyte unknown. Upper lamina KOH color reaction reddish orange. Didymodon anserinocapitatus is here reported for the New World from two sites in the foothills of the Rocky Mountains on the eastern edge of the Colorado Plateau. COLORADO. Fremont Co., 4.5 km up lower portion of Phantom Canyon, tributary of lower Arkansas River between Pueblo and Canyon City, red sandstone cliffs, 1,500-2,200 m elev., Weber, Hermann & Feddema B-37528, 1 June 1971 (COLO) and NEW MEXICO: San Miguel Co., Pecos, along Pecos River, (no substrate given), 2,100 m elev., Richards & Drouet 456, 21 Oct. 1939 (DUKE). This species is known otherwise only from the type locality in Tibet. The arctic-northern montane species Didymodon johansenii (Williams) Crum is similar in the swollen, deciduous apex, but differs mainly by its larger upper laminal cells (13-15 pm wide), and guide cells in only a single layer. Didymodon rigidulus var. icmadophilus (C. Mtill.) Zand., a wide-spread montane-grassland species, is similar in appearance but its leaf apices are never swollen (though sometimes fragile). Didymodon rigidulus var. subulatus (Th6r. & Bartr.) Zand. of Arizona and Mexico has bito tri-stratose, longcylindric, very fragile leaf apices, but the apices mostly taper (rarely being barely widened). Through the plane margins of the leaves and the somewhat knotted apex, the latter variety is most closely related to D. rigidulus var. icmadophilus. The Colorado and New Mexican specimens cited above are similar in size and most other respects to material from China (TIBET, Nan Xian, Zang Mu 1704, isotype-NY), but differ in the propagulum usually widest in the middle while that of the Tibetan material is usually widest below the middle and is often slightly larger. In the key to taxa of Pottiaceae with propaguliferous apices (Zander 1978), D. anserinocapitatus would key to D. johansenii. Didymodon anserinocapitatus is very closely related to D. johansenii and D. sinuosus (Mitt.) Delogn. according to a cladistic study (Zander, in prep.). Didymodon anserinocapitatus shares a similar disjunct distribution pattern with many mosses and some lichens. This pattern reflects a relationship between the floras of the Colorado Plateau and central Asia. Mosses with central or central-western North America and central Asia disjunctive distributions (most with outliers elsewhere) include Anacolia laevisphaera (Tayl.) Flow., A. menziesii (Turn.) Par., Grimmia elatior Bals. & De Not., Jaffueliobryum raui (Aust.) Th6r., J. wrightii (Sull.) Th6r., Leptodon smithii (Hedw.) Web. & Mohr, Leptop0007-2745/97/237-238$0.35/0 This content downloaded from 157.55.39.52 on Tue, 12 Jul 2016 06:17:39 UTC All use subject to http://about.jstor.org/terms 238 THE BRYOLOGIST [VOL. 100