Townsendia lemhiensis C.Lee, Bjoerk & Whitton, 2022

Lee, Christopher, Bjoerk, Curtis R. & Whitton, Jeannette, 2022, Townsendia lemhiensis (Asteraceae, Astereae): A narrowly endemic new species from Idaho, USA, PhytoKeys 193, pp. 67-75 : 67

Townsendia lemhiensis C.Lee, Bjoerk & Whitton sp. nov.

Holotype.

Björk 29248 (UBC V252324) 20 May 2012. USA, Idaho, Lemhi County, 18 Mile Wilderness Area, ca. 24 km SSE of Leadore, 44.44806°N, 113.17222°W, on dry ashy white soil on slope (7368 ft) in sagebrush steppe (Fig. 1A ). Paratypes: Björk 30627 (UBC V252325) 14 May 2013. USA, Idaho, Lemhi County, 18 Mile Wilderness Area, on a ridge crest near the middle road, 44.46707°N, 113.22570°W, on ashy white slope, sparsely vegetated, soil derived from tuff conglomerates, in upper elevation (6968 ft) sagebrush steppe in intermontane valley; Björk 30772 (UBC V252326) 21 May 2013. USA, Idaho, Lemhi County, 18 Mile Wilderness Area, south of McFarland Road, 44.48000°N, 113.20333°W, on ashy white flats and slopes, sparsely vegetated, in upper elevation (6857 ft) sagebrush steppe in intermontane valley; Whitton 252 (UBC V252322) 13 May 2018. USA, Idaho, Lemhi County, 18 Mile Wilderness Area, 44.47293°N, 113.20670°W, on open hillside (7355 ft) with sparse sagebrush and antelope brush on grey-brown rocky substrate; Whitton 256 (UBC V252323) 14 May 2018. USA, Idaho, Lemhi County, 18 Mile Wilderness Area, 44.44530°N, 113.17541°W, on exposed rocky slope (7371 ft), in areas of grey-white substrate, with bunchgrass, and antelope brush.

Ab Townsendia spathulata pappi ad maturitatem persistens, series phyllariorum pauciores, pilis caulibus sericeus non villosus, folia non carnosa differt.

Description.

Plants perennial, 25-30 mm tall, rosette forming, rosettes 8-17 mm wide, solitary or (more often) arising from a few-branched caudex; stems essentially absent, or when visible, then villosulous; leaves 4-14 × 2 mm, narrowly oblanceolate to narrowly elliptic-oblanceolate, silvery, moderately sericeous but not villous, apex acute; capitula one per fertile rosette, sessile or nearly so; involucre campanulate, 9-10 mm wide, phyllaries appressed, narrowly elliptic-lanceolate, 6-7 × 1 mm, graduated, in 2-3 series, reddish brown, sericeous, apex acute to acuminate; ray florets 15-24, pistillate; ray corollas true ray, 7-8 mm long, surpassing pappus bristles, light brownish pink or whitish and tipped in pink, slightly darker abaxially, aglandular; disc florets 24-30, functionally pistillate; disc corollas tubular, 4 mm long, shortly surpassed by the pappus bristles, yellow, aglandular; stamens reduced to strap-like staminodes, anthers and pollen absent; cypselae 3 × 1 mm, oblanceolate and compressed, with glochidiate hairs; pappus bristles 23-26 in disc florets, 14-20 in ray florets, 6-7 mm long, white, barbellate, persistent. (Figs 1B-D , 2A-F ).

Etymology.

Townsendia lemhiensis is named after the Lemhi Valley, Idaho, where individuals of this species were first noticed by Curtis Björk.

Distribution and habitat.

Townsendia lemhiensis is known only from the Lemhi Valley in east-central Idaho, which is situated within a region known for its numerous geographically endemic plants ( Moseley and Conley 1989; Moseley et al. 1990; Ertter and Moseley 1992). The species has been found in three populations, within an area of 4.9 km2.

Townsendia lemhiensis grows on ashy white slopes of eroded rhyolite tuff. These slopes of powdery soils and friable rock are sparsely vegetated, forming edaphic islands of open ground within a more densely vegetated surrounding matrix of sagebrush steppe. Numerous other plants having narrow geographical ranges occupy similar ashy slopes elsewhere in dry interior regions of western North America ( Grimes 1984; Reveal and Björk 2004; Brown and Mansfield 2017). The Lemhi Valley is lined on the east and west by alpine ridges, and the valley floor sits at a high elevation, making it cooler than the sagebrush steppes both further south on the adjacent Snake River Plains and further north in the Salmon-Challis Valleys region.

Associated species growing with Townsendia lemhiensis on the ashy slopes include: Artemisia frigida Willd., 1838, Artemisia tridentata subsp. wyomingensis Beetle & A.L.Young, 1965, Chaenactis douglasii Hook. & Arn., 1839, Comandra pallida A.DC., 1857, Cymopterus bipinnatus S.Wats., 1885, Elymus lanceolatus (Scribn. and J.G.Sm.) Gould, 1949, Eriogonum mancum Rydb., 1917, Eriogonum soliceps Reveal & Björk, 2004, Ipomopsis spicata subsp. orchidacea (Brand) D.Wilken & R.L.Hartm., 1991, Linum lewisii var. alpicola Jeps., 1936, Oreocarya humilis Greene, 1896, Packera cana (Hook.) W.A.Weber & Á.Löve, 1981, Penstemon humilis Nutt. ex A.Gray, 1862, Phlox muscoides Nutt., 1831, Stenotus acaulis (Nutt.) Nutt., 1840, Townsendia hookeri Beaman, 1957, T. leptotes (A.Gray) Osterh., 1908, and T. parryi D.C.Eaton, 1874.

Phenology.

We observed T. lemhiensis in flower in mid-May over three years (2012, 2013, 2018). At this time, some individuals had some capitula in bud, and others had mature seeds or open flowers. On this basis, we describe flowering as likely occurring throughout May, and seedset through late May or possibly into June. Further studies are needed to document the timing of bud formation, and potential variation in flowering and fruiting phenology. Another early-flowering species, Townsendia hookeri , co-occurs with T. lemhiensis , and has been observed to set buds in fall that open soon after snow melt (Lee and Whitton, personal observation). Given the early flowering of T. lemhiensis and the presence of snow patches persisting in surrounding areas, we suspect fall bud set may also occur in this species. Co-occurring species of Townsendia were found on site in bud ( T. parryi ) and late-bud ( T. leptotes and T. hookeri ).

Figures

Figure 1. A habitat of the type locality of Townsendia lemhiensis B habit of Townsendia lemhiensis at the type locality C close-up of Townsendia lemhiensis capitulum D close-up of Townsendia lemhiensis phyllaries. Photos A-B by Bjoerk; Photos C-D by Whitton.

Figure 2. A capitulum B outer involucral bract C inner involucral bract D ray floret E disc floret F mature disc cypsela. Photos by Spencer Goyette (UBC Herbarium).