Adiantum shastense Huiet & A.R.Sm., 2015

Huiet, Layne, Lenz, Martin, Nelson, Julie K., Pryer, Kathleen M. & Smith, Alan R., 2015, Adiantum shastense, a new species of maidenhair fern from California, PhytoKeys 53, pp. 73-81 : 74-77

Adiantum shastense Huiet & A.R.Sm. sp. nov. Figs 1 , 2

Diagnosis.

Adiantum shastense is similar to Adiantum jordanii in having dark brown to purplish brown rhizome scales and 2-3-pinnate laminae. It differs by being persistent and green throughout the summer, and does not die back as does Adiantum jordanii . Adiantum shastense can be distinguished from Adiantum capillus-veneris by the darker rhizome scales, the rhomboid shape of the pinnulets, and the often, glaucous bluish green color of the laminae.

Type.

UNITED STATES, California: Shasta County, north side of Lake Shasta. McCloud River arm, along Gilman Road, just W of intersection with Old Mill Road where Fall Creek intersects Gilman Road. 40°51.517200'N, 122°18.835800'W, 1222 ft, 14 May 2014, Layne Huiet, Alan Smith, Joan Smith, Ellen Dean & Martin Lenz 162 (holotype: UC2030515!; isotypes: CAS!, DAV!, DUKE!, MO!, NY!, US!)

Description.

Rhizomes short-creeping or ascending, usually buried in loose soil, 2-4 mm in diameter, sometime branching; stipes clustered, up to 10 fronds per 1 cm of rhizome length; rhizome scales (and those at stipe base) castaneous to dark brown, lustrous, concolorous, ovate to lanceolate, attenuate at tips, 1.5-5 × 0.3-0.6 mm, margins entire; fronds clustered, mostly (18-)30-60 cm long, arching, persisting (remaining green) through summer, fall, and into winter; older dead fronds remaining attached to rhizome behind new growth; stipes castaneous to atropurpureous, becoming blackish with age, sublustrous, sometimes slightly glaucous (especially proximally), terete, each with a single vascular bundle at bases, (10-)20-30 cm long, (0.6-)0.8-2.0 mm in diameter, ca. 1/2 the frond length, glabrous except at very bases; laminae ovate to deltate, 2-3 times pinnate (depending on size), mostly (12-)20-35 × (6-)15-20 cm, broadest at or just above the bases, tapering gradually to apices, costae (pinna axes) ascending mostly 30-50 degrees from rachis, pinnae acroscopically branched, basal acroscopic pinnule longer, more dissected, and at a greater angle with respect to costa than basal basiscopic branch (pinnae thus somewhat unequal-sided), laminae bluish green, often slightly glaucous; rachises castaneous to atropurpureous, glabrous, lustrous or slightly glaucous, terete to somewhat angled or obscurely sulcate adaxially (more so distally); pinnae of well developed laminae ca. 6-8 pinnate to bipinnate pairs below the 1-pinnate apical region (which is 3-5 cm long), decidedly alternate, stalked to ca. 2 cm (proximal pinnae); pinnulets (ultimate segments) obovate, flabellate, or rhombic, sometimes semicircular, non-articulate except on very old laminae (stalks not breaking cleanly, not cupule-like at their apex), mostly 1-2 × 1-2 cm (to 2 × 3 cm in sterile segments of juvenile fronds), cuneate at bases ca. 90-135 degrees (more narrowly cuneate bases on distal segments), occasionally pinnulet bases truncate and the pinnulets thus semicircular (especially proximal acroscopic pinnulet on well-developed pinnae), margins often cleft 1-4 mm, sterile pinnulets generally more incised than the fertile, 1-3 clefts per pinnulet, sterile margins thickened, whitish, shallowly crenulate distally, color of stalks gradually diminishing at base of pinnulets and passing slightly into pinnulet lamina; veins free, forking, in sterile laminae ending in small rounded crenulations (not in sharp teeth) of pinnulet margins, usually visible but only slightly raised, if at all, on both sides of laminae; indument lacking on both sides of laminae; idioblasts not apparent either abaxially or adaxially; sori 2-7 per pinnulet, confined to distal margins, sporangia borne on ± parallel veins on the strongly reflexed underside of the indusia (facing laminar tissue), mixed with sessile yellow-orange, cylindrical or clavate glands <0.1 mm long; indusia mostly (1-)2-4 mm long, ca. 1 mm wide, entire or nearly so, oblong to slightly arcuate (not noticeably reniform), lacking hairs. 2n = 30 II.

Distribution and ecology.

Adiantum shastense is currently known only from an area of the Eastern Klamath range ( Miles and Goudy 1997) surrounding Shasta Lake entirely within Shasta County, California. It is found in mesic hardwood-conifer forests, on the forest floor as well as on limestone and metasedimentary rock outcrops, including rocky road cuts, most often in shade and with northern or eastern exposures. It co-occurs with the local endemic Shasta snow wreath, Neviusia cliftonii Shevock, Ertter & D.W.Taylor. In some localities it can be the dominant understory plant (Fig. 1a ). Associated species include Pinus ponderosa P.Lawson & C.Lawson, Quercus chrysolepis Liebm., Acer macrophyllum Pursh, and Toxicodendron diversilobum (Torr. & A.Gray) Greene. Collected from 1100-2740 ft (335-835 m) elevation.

Phenology.

Sporulates mid to late spring and most likely throughout summer.

Etymology.

It seems most appropriate to name this species Adiantum shastense , recognizing its restricted, currently known geographic localization to Shasta Co., California.

Suggested common name.

Shasta maidenhair fern.

Conservation status.

We recommend a California Rare Plant Rank of 4.3, a watch list for plants of limited distribution.

Paratypes.

U.S.A. California: Shasta Co.: 2.6 miles E of Nosoni Mountain on the west side of North Fork Squaw Creek, 2700 ft, 07 Apr 2009, P.J. Alexander 994 (DUKE!, NMC, SP); Waters Gulch Trail ca. 05 mi N of Packers Bay Marina, 1200 ft, 27 Apr 1994, Oswald & Ahart 6148 (CHSC, JEPS!); Bailey Cove Trail, W side of McCloud River arm of Shasta Lake, 1100 ft, 27 Apr 1994, Oswald & Ahart 6121 (CHSC, JEPS!); Oak Run, 21 May 1894, Baker & Nutting s.n. (UC!); on limestone cliffs 0.5 mi E of Squaw Creek fire control station, 1750 ft, 19 Apr 1992, Taylor 12599 (JEPS!); south side of Lake Shasta, Pit River Drainage along Fenders Ferry Rd, 1730 ft, 15 May 2014, Huiet et al. 167 (DAV!, DUKE!, UC!); on arm of McCloud Reservoir across from boat ramp, ca. 8.5 air miles SSE of McCloud, 2740 ft, 27 May 2014, Lenz & Nelson 5350 (DUKE!, UC!); along road to Deep Creek campground, ca. 5.2 air miles SE of Big Bend, 2395 ft, 27 May 2014, Lenz & Nelson 5351 (DUKE!, UC!); along logging road on east side of Sacramento River across from Gibson, 2045 ft, 27 May 2014, Lenz 5352 (DUKE!, UC!); McCandless Gulch ca. 5 miles E of Ingot, 1700 ft, 16 Sept 2014, Taylor, Falscheer & Lindstrand 21512 (DAV!, UC!); Cedar Creek drainage, ca. 6 miles west of Round Mountain on Highway 299, 1450 ft, 6 Sept 2013, Taylor 21418 (UC!); along Fender’s Ferry Rd. ca. 6.5 road miles SE of McCloud Bridge, 1800 ft, 3 Jul 2014, Alverson 2014-10 (OSC, UBC, WTC!); north side of Lake Shasta, McCloud River Arm, Bailey Cove Trail, 1135 ft, Huiet et al. 156A (DUKE! chromosome voucher).

Figures

Figure 1. Photographs of Adiantum shastense. A Plants as dominant understory in one locality B Mature plant C Fronds D Young fertile pinnulets.

Figure 2. Holotype of Adiantum shastense Huiet & A. R. Sm. (Huiet et al. 162, UC)