Didymodon californicus J. A. Jimenez, Toren & Shevock 2014, sp. nov.
Creators: name: Jiménez, Juan A.
name: Toren, David
name: Shevock, James R.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Plantae
Bryophyta
Bryopsida
Pottiales
Pottiaceae
Didymodon
Didymodon californicus

description: Didymodon californicus J. A. Jiménez, Toren & Shevock sp. nov. (Figs. 1, 2)
Diagnosis: Didymodon californicus differs from the otherwise similar Didymodon vinealis Bridel (1827: 830) Zander (1978: 25) in its obtuse or widely acute leaf apex not ending in a conical cell, plane leaf margins throughout and costa ending below the apex.
TYPE:— U.S.A. California: Fresno County, Sierra National Forest along road 8S05 above the San Joaquin River Canyon, 2.2 miles NE of Stevenson Creek. T8S, R24E, section 33, 37º12'15''N, 119º19'55''W, 731 m, 21 Apr 2001, Shevock & Norris 20632 (holotype: CAS; isotype: MUB).
Plants 2–5.3 cm high, growing in dense turfs, green or green-brown to red-brown; stems erect, irregularly branched, not radiculose, without hyalodermis, sclerodermis differentiated, central strand weakly developed; axillary hairs filiform, 3–4 cells long, with 1(–2) brown basal cell and hyaline upper cells. Rhizoidal tubers absent. Leaves appressed to strongly incurved, seldom slightly twisted when dry, erect-patent or more rarely spreading when moist, often rather distant, lanceolate to widely-lanceolate, base sometimes ovate, 1.7–3.1 × 0.6–0.95 mm, channelled ventrally in the upper part, lamina unistratose, sometimes juxtacostal lamina cells bistratose in several rows, red to reddish orange with KOH; apex obtuse or widely acute, not cucullate; margins plane, unistratose, very seldom irregularly bistratose in 1(–2) rows of cells in distal part, often decurrent on stem; costa strong, 70–150 µm wide at base, ending 2–5 cells below the apex, sometimes sinuose above midleaf, not spurred; ventral surface cells of the costa subquadrate to oblate, smooth, vanishing near the apex, and replaced by a hyaline area of widely rectangular cells, dorsal surface cells of the costa subquadrate to oblate, smooth, in cross-section below midleaf semicircular, with 2–3 layers of guide cells, with 4–6 cells in each layer, without ventral stereids, 1–2 layers of dorsal stereids present, lunulate in shape, without hydroids, ventral surface cells differentiated, smooth, dorsal surface cells differentiated, smooth; upper and middle lamina cells subquadrate, rounded or oblate, 3.2–8(–9.6) × 3.2–8(–9.6) µm, essentially smooth, sometimes with low papillae, not bulging, thick-walled; juxtacostal basal cells quadrate to shortly rectangular, 7.5–30(–35) × 0.5–12.5 µm, smooth, not bulging, slightly and evenly thick-walled; marginal basal cells mostly oblate, some subquadrate, 3.2–9.6 × 6.4–16 µm, smooth, not bulging, transversely thick-walled, forming a differentiated area. Gemmae absent. Perigonia, perichaetia and sporophytes unknown.
Additional specimens examined: — U.S.A. CALIFORNIA: Glenn County, Mendocino National Forest, along forest highway M-3, 4.9 miles southeast of Ivory Mill Saddle and 3.9 miles northeast of Sheetiron Mountain, 39º31'30''N, 122º41'00''W, 1509 m, 2 Jul 1997, Shevock 15818 (CAS, MO, MUB, NY). Lake County, Mendocino National Forest, east of Crockett Peak along old un-numbered logging road south of Forest Road M3 and southwest of Waters Camp, 39º26'00''N, 122º45'25''W, 1646 m, 12 Jul 2012, Toren & Dearing 9926 (CAS, MUB). Madera County, Sierra National Forest along Minarets Road, 1.8 miles north of Fish Creek and 1.5 miles south of Slide Creek, 37º16'30''N, 119º21'30''W, 1372 m, 29 Jul 2000, Shevock & Norris 19786 (CAS, MUB).
Etymology: —The epithet californicus refers to the State of California where this species appears to be a regional endemic.
Habitat and distribution: — Didymodon californicus, based on the known occurrences, is viewed as a semirheophytic species where it is seasonally submerged or inundated during snowmelt and peak rain events along perennial and intermittent streams. However, during most of the year the plants are dry. This ecological partition of habitat along the high water zone of stream and river banks is also similar to that displayed by Didymodon insulanus De Notaris (1838: 320) Hill (1981: 599) and D. nicholsonii Culmann (1907: 100). Both of these species are frequently encountered along streams and rivers where they too are seasonally submerged. Even some California populations of Didymodon vinealis can be viewed ecologically as being rheophytic where the plants form flat mat-like colonies, over rock slabs with seasonal water flow, more reminiscent of the growth pattern of Schistidium cinclidodonteum (Müll. Hal. in Röll 1890: 387) Bremer (108: 1980) populations. This may explain why this new species of Didymodon has been overlooked and under-collected. Many bryologists defer collecting these common species, especially when sporophytes are lacking.
Didymodon californicus occurs in the central Sierra Nevada and the northern Coast Ranges of California (Fig. 3). All known occurrences are on public land providing various opportunities for long-term conservation.
description: Published as part of Jiménez, Juan A., Toren, David & Shevock, James R., 2014, Didymodon californicus (Pottiaceae), a new species from California, U. S. A., pp. 105-110 in Phytotaxa 158 (1) on pages 105-108, DOI: 10.11646/phytotaxa.158.1.9, http://zenodo.org/record/5128216