Eriogonum domitum Grady & Reveal, 2011

Grady, Ben R. & Reveal, James L., 2011, New combinations and a new species of Eriogonum (Polygonaceae: Eriogonoideae) from the Great Basin Desert, United States, Phytotaxa 24, pp. 33-38 : 37-38

Eriogonum domitum Grady & Reveal , sp. nov.

A Eriogono manco foliis ellipticis ad orbiculatis (nec oblanceolatis ad spatulatis) et involucris rigidis (nec membranaceis) differt.

Type: — U.S.A.: Utah: Millard County, House Range, NE slope of Notch Peak ca. 100 m below summit, exposed limestone cliff edges in thin, silty, limy soil, associated with Cercocarpus and Ephedra , 39°08′35.6″N, 113°24′25.7″W, T 19 S, R 14 W, Sec. 22, 2832 m (9293 ft) elev., 6 July 2010, Grady & Heyduk 638 (holotype NY, isotypes BH, BRY, US, UTC, WIS, and elsewhere).

Plants low, pulvinate perennial herbs forming mats to 1 dm across from underground branching caudex; leaves basal, semi-erect, fasciculate in terminal tufts, the petioles (1–) 3–6 mm long, tomentose, the leaf-blades elliptic to orbicular, (5–)6–12 × (3–) 5–9 mm, densely grayish tomentose abaxially, less so and greenish adaxially, the apex and leaf base rounded, the margins plane; flowering stems scape-like, erect to semi-erect, 2–5(–5.5) cm, tomentose, grayish; inflorescences capitate, (0.8–) 1–1.5 cm wide; bracts 5–6, scale-like, 1–2.5 mm long, narrowly triangular; peduncles lacking; involucres congested, 4–7, campanulate, rigid, (1.5–)2–3 × 1.5–2(–2.5) mm, tomentose, the teeth 5, 0.6–1.0(–1.2) mm long; flowers 2.5–3.5 mm long on pedicels 2–3 mm long, the perianth white to pink to rose or magenta with red midvein, glabrous, the hypanthium 1/3–1/2 length of perianth, the tepals monomorphic; stamens exserted, 2–3 mm long, the filaments usually sparsely pilose basally; achenes trigonous, light brown, 2–2.5(–3) mm long, glabrous except for a minutely papillate beak.

Distribution and habitat:— Like many other capitate members of Eriogonum subg. Eucycla , E. domitum is a narrowly distributed edaphic endemic species. As such, E. domitum is known only from high limestone ridges in the House Range of west-central Utah. The House Range wild buckwheat occurs in a fairly narrow elevation band of 2760–2900 m, higher than the pinyon-juniper woodland. Individuals are found most often in a thin limy soil that accumulates in fractures of Notch Peak limestone. This species has only been observed by the authors flowering in July, but presumably produces flowers in June, continuing into August.

Etymology:— The specific epithet, domitum , means “of the house”, referring to the House Range, to which this species is endemic.

Observations:— Morphologically, Eriogonum domitum resembles E. mancum , the former previously considered to be a relict population of that more northerly species ( Reveal 2005). Ongoing molecular studies indicate that E. domitum has a distinct evolutionary history from that of E. mancum (Grady & Sytsma, unpublished data). In the field, these species can be distinguished by the leaf blade shape and the appearance of the involucres. The leaves of E. domitum are elliptic to orbicular on a well-defined petiole, while those of E. mancum are oblanceolate to spatulate with the blade grading into the petiole. The involucres of E. domitum are distinctly rigid and turbinate in shape, as compared to the membranous, open-campanulate involucres of E. mancum . Geographically, these two species are separated by nearly 500 km.

Eriogonum holmgrenii Reveal (1965: 184) , another capitate member of subg. Eucycla , also occurs on high-elevation calcareous substrates in the eastern portion of the Great Basin Desert. Although E. holmgrenii and E. domitum are separated by only ca. 80 km, much of the intervening area is low-elevation basin, with a drastically different moisture regime and geology than either species currently occupies. Though similar ecologically, these two species are easy to distinguish based on pubescence. Glandular trichomes cover the flowering stems, leaves and the perianth of E. holmgrenii . All trichomes on the vegetative and floral structures of E. domitum are simple and non-glandular.

The species will be illustrated in a forth-coming volume of the Intermountain Flora.

Additional specimens examined (paratypes):— U.S.A. Utah: Millard Co.: House Range, summit of Pine Peak ca. 1.5 air mi N of Notch Peak , limestone outcrops and gravel, gray silty-limy soil, 39°09′59.3″N, 113°24′33.3″W, T19 S, R14 W , Sec. 10, 2820 m (9250 ft) elev., 22 July 2009, Grady 575 ( NY, WIS); ca. halfway between Pine Peak and Notch Peak , steep ridgeline of limestone gravel, gray silty-limy soil, 39°09′23.2″N, 113°24′38.5″W, T19 S, R14 W , Sec. 15, 2830 m (9285 ft) elev., 22 July 2009, Grady 578 ( WIS); House Range , limestone ridge ca. ½ mi ESE of Notch Peak, silty, limy soil and limestone gravel and cobbles, 39°08′29.2″N, 113°24′06.1″W, T19 S, R14 W , Sec. 22, 2765 m (9072 ft) elev., 6 July 2010, Grady & Heyduk 636 ( WIS) .