A new Ranunculus species, Ranunculus basalticus Giblin sp. nov., is described from sagebrush-steppe and low elevation grassland areas of south-central Washington. The species is close in appearance to two sympatric Ranunculus species, the narrow endemic R. triternatus A.Gray and the broadly distributed R. glaberrimus Hook. However, discrete morphological, ecological, and distribution differences easily separate R. basalticus from these other species. The earliest record of R. basalticus dates to 2004 in the form of a digital photo, with subsequent voucher specimens first collected in 2009. Additional field collecting, along with photo submissions to iNaturalist, suggest that R. basalticus is a narrow endemic of Kittitas, Klickitat, and Yakima counties in Washington. It most commonly occurs in soil-stabilized basalt talus, for which the specific epithet refers. Although R. basalticus appears to have a narrow distribution, within its range, population sizes can exceed 100 plants. All currently documented populations are on public lands managed for multiple uses, though there appear to be no direct threats to these populations.
Ranunculus L. is a cosmopolitan genus with more than 600 species occurring in diverse habitats from sea level to the alpine (Tamura 1995). The most recent comprehensive treatment for Ranunculus in North America north of Mexico reports 76 species (Whittemore 1997), although that treatment does not reflect the later segregation of several small genera, such as Arcteranthis Greene, Beckwithia Jeps., Ceratocephala Moench, Ficaria Guett., and Halerpestes Greene to create a monophyletic Ranunculus (Emadzade et al. 2010). Hybridization and polyploidy have contributed to diversification in the genus, with introgression among sympatric taxa well-documented (Liao et al. 2008; Hörandl et al. 2009; Cruzan et al. 2021; Bobrov et al. 2022).
A total of 22 Ranunculus species comprising 40 taxa are currently reported from Washington State in western North America (Legler 2018). With the exception of one narrowly endemic species (R. triternatus A.Gray), these taxa are broadly distributed either regionally or continentally, and none is reported to form hybrid swarms where sympatric in the Pacific Northwest (Legler 2018).
Ranunculus glaberrimus Hook. is broadly distributed across western North America from British Columbia to California, east to the Rocky Mountains and northern Great Plains. In Washington it most frequently occurs east of the Cascades crest in sagebrush desert and ponderosa pine forest openings between 100–800 m, although alpine populations do occur on the eastern edge of the Olympic Mountains in western Washington. The species is easily recognized by its simple leaves with blades that range from narrowly elliptic to reniform with apices that vary from entire to deeply three-lobed.
Ranunculus triternatus is endemic to the eastern Columbia River Gorge area of Klickitat County, Washington, and adjacent Hood River and Wasco counties in Oregon (Legler 2018). Flora of North America reports isolated populations of this taxon in Nevada and Idaho (Whittemore 1997); however, we and other researchers were unable to locate those specimens and consider such occurrences unlikely (Holmgren and Holmgren 2012). As the specific epithet indicates, the leaves are triternate, and the leaflet lobes are linear. Although R. triternatus occurs at elevations between 150–1000 m, similar to that of R. glaberrimus across its range, voucher- and photo-based evidence suggest that these two species seldom if ever occur in close proximity in this area (Consortium of Pacific Northwest Herbaria 2023, iNaturalist 2023). Additional studies are needed to determine potential microsite differences between known occurrences.
In 2009, specimens of Ranunculus were collected in Klickitat County, Washington, in oak savannah habitat with ternate basal leaves that could be interpreted as intermediate in leaf morphology to both R. triternatus and R. glaberrimus. Additional specimens of such plants have since been collected from other locations in Kittitas, Klickitat, and Yakima counties of Washington through 2023, and images of such plants from yet more locations appear on iNaturalist (2023) and the Burke Herbarium Image Gallery (2023) dating as far back as 2004. Subsequent examination of specimens at WTU and additional field work indicate that the plants with ternate basal leaves also have nectary gland and achene beak morphologies that differ from those of either R. glaberrimus or R. triternatus. Field work has also shown that the plants with ternate basal leaves do not form hybrid swarms where they co-occur with R. glaberrimus. Finally, the range of this form is only minimally sympatric with R. triternatus, where they share a southern and northern distribution edge, respectively, but do not co-occur in proximity to one another. Based on distinct leaf, flower, and fruit morphologies (Figs. 1, 2), lack of apparent interbreeding with R. glaberrimus, and discreet distribution differences from R. triternatus (Fig. 3), we believe it is best to recognize those plants with ternate basal leaves at the rank of species, which we describe here as Ranunculus basalticus Giblin. Based on the key for the Flora of North America Ranunculus treatment, this species would belong to the section Epirotes (Whittemore 1997).
Fig. 1.
Ranunculus basalticus. A. Habit. B. Ternate leaf. C. Achene with curved beak and short hairs. D. Petal with notched nectary and adjacent illustration highlighting undulating nature of nectary surface. Illustrations based on type specimens. Illustrations by Crystal Shin.
Fig. 2.
Photos of Ranunculus basalticus habitat, growth habit, and nectary morphology. A. Example of soil-stabilized basalt scree where Ranunculus basalticus often grows. Photo by Peter Zika. B. Ranunculus basalticus growing in basalt talus (Photo by David Giblin). C. Ranunculus basalticus nectary. Photo by David Giblin. D. Ranunculus triternatus illustration highlighting triternate leaves and deeply notched nectary. Illustration by Jeanne R. Janish.
Fig. 3.
Map of study area, with inset showing location of study area in Washington and adjacent Oregon. Geographic distribution of R. basalticus (filled triangles - specimens; open triangles iNaturalist observations) and R. triternatus (filled circles - specimens; open circles - iNaturalist observations). The two species are sympatric only at their known southern and northern ranges, respectively. Map by John Haskins.
Taxonomic Treatment
Ranunculus basalticus Giblin, sp. nov. (Figs. 1, 2). TYPE: USA, Washington, Kittitas Co., Yakima River Canyon. West side of Yakima River, approximately 300 m west along and 200 m south of trail; north-facing soil-stabilized basalt scree slope, 430 m elevation, 46.85392, –120.48814, 25 April 2023, Giblin 8974. (holotype: WTU 433410; isotypes: OSC, US, WS).
Perennial herbs, 5–25 cm, glabrate, cespitose. Roots fibrous-thickened, to 15 cm long, tapering only slightly throughout their length. Stems lax, sometimes arcuate, generally longer than high, red when young, drying brownish, with conspicuous to inconspicuous longitudinal ribs. Leaves basal, 5–15, long-petiolate, petioles to 8 cm; blades ternate, occasionally simple and lobed to base, wider than to as wide as high, 6–22 × 15–32 mm, lightly bluish-green; leaflets mostly sessile, occasionally on flattened petiolules to 4 mm long, usually with three deeply divided lobes; leaflet lobes (0-)3(-5), 2–22 × 1–10 mm, shallowly to fully cleft, broadly oblanceolate to ovate or obovate, margins entire. Inflorescences with 1–2 bracts, bracts ternate, occasionally simple and lobed to base, from wider than high to higher than wide, 2.5 cm × 2.5 cm, bractlets or bractlet lobes oblanceolate to ovate or obovate, margins entire; flowers typically terminal and solitary, occasionally also axillary. Peduncles 3–15 cm at anthesis, mostly glabrate, occasionally short-hairy at base of receptacle, elongating in fruit. Receptacles sparsely hairy with crisped hairs to 0.5 mm; globose at anthesis, elongating to 7 mm in fruit. Flowers bisexual; sepals 5(6), free, often red and gibbous when young, brownish-green at maturity, glabrous, 5–9 × 3–6 mm, ovate-elliptic, with conspicuous, mostly parallel veins; petals 5, free, yellow, sometimes drying white, glabrous, 7–13 × 5–11 mm, obovate with short, broad claw, veins conspicuous, branching distally; nectary to 2 mm, golden, margins adnate with petal nearly entire length, distal margin entire to shallowly bifid, eciliate; stamens clavate, anther sacs to 1.2 mm, confluent with filaments, dehiscing abaxially; filaments flattened at anthesis, to 3 mm in length at maturity; carpels 25–40, glabrous at anthesis with straight, flattened beak; Fruits mature achenes to 2 mm long, sparsely short-hairy, moderately compressed laterally, keeled dorsally, beak strongly curved to uncinate.
Paratypes. USA. Washington, Kittitas Co., Umtanum Creek Recreation Area. West side of Yakima River, approximately 300 m west along trail and 200 m south of trail, 430 m elevation, 46.5392, –120.48814, 28 April 2023, Giblin 8965 (WTU); Klickitat Co., Klickitat State Wildlife Recreation Area west of the Glenwood Highway. Canyon Creek, a tributary of the Little Klickitat River. Volcanic rock outcrop above creek on east side of drainage, elevation 365 m, 45.8653, –121.00915; 1 April 2009, Carolyn Wright 2241 (WTU); Klickitat State Wildlife Recreation Area. Canyon Creek. Middle of west-facing slope on east bank of Canyon Creek. 508 m elevation, 45.8890, –121.0538; 23 April 2009, Paul Slichter, s.n. (WTU); Klickitat State Wildlife Recreation Area west of the Glenwood Highway. East slope above Canyon Creek. Volcanic rock outcrop, elevation 425 m; T5N, R14E, sect. 34; 3 May 2009, Carolyn Wright 2242 (WTU); Klickitat State Wildlife Area, Canyon Creek. Plants in open, steep, rocky basalt swales, slope 30–40°, occasionally less, 1162 ft elevation [352 m], 45.863403, –121.041449; 21 March 2014, Paul Slichter, s.n. (WTU); Klickitat State Wildlife Recreation Area. Canyon Creek. 370 m elevation, 45.8653, –121.0414; 21 March 2014, Paul Slichter, s.n. (WTU); Klickitat State Wildlife Recreation Area. Canyon Creek, elevation 355 m, 45.8634, –121.0414; 21 March 2014. Paul Slichter, s.n. (WTU); Yakima Co., Oak Creek Wildlife Area. Bear Canyon. Approximately 0.75 km from trailhead, west side of trail; elevation 640 m; 46.70875, –120.89615; 25 May 2022, David Giblin 8706 (WTU); Oak Creek Wildlife Area. Bear Canyon. Approximately 0.75 km from trailhead, west side of trail, 50 m elevation higher upslope than David Giblin 8706 site, elevation 690 m, 46.70848, –120.89671; 25 May 2022, David Giblin 8708 (WTU); Oak Creek Wildlife Area. South side of Tieton River, elevation 520 m, 46.72654, –120.80789, 25 April 2023. Giblin 8996 (WTU); Oak Creek Wildlife Area. Bear Canyon. Approximately 50 m north from parking area, elevation 613 m, 46.70669, –120.89127; 25 April 2023. Giblin 9000 (WTU).
Distribution and Habitat
Range. endemic to Kittitas, Klickitat, and Yakima counties in Washington. Habitat: Quercus garryana Douglas ex Hook. savannah, partially vegetated scree and talus of grassy slopes, and basalt ledges; 300–700 m.
Etymology
The specific epithet basalticus refers to the basalt scree and talus slopes where this species is found. On this basis the recommended common name is Basalt Buttercup.
Discussion or Conservation Implications
Within Rabinowitz's (1981) seven forms of rarity framework, R. basalticus is a narrowly distributed habitat specialist. Despite its narrow distribution, specimen and online photo data indicate at least 15 localities for R. basalticus. Field work to date has documented several populations with robust numbers (e.g., more than 100 plants in a population). However, our field observations suggest that the habitat preferences for this species is rather narrow, with it showing almost exclusive preference for thin soils that develop over basalt scree, talus, or ledges. It is not found in adjacent areas lacking exposed basalt or in areas of exposed basalt lacking soil (i.e., it does not grow up through openings in basalt talus).
All documented populations of R. basalticus occur on state and federal public lands managed for multiple uses (e.g., recreation, cattle grazing, hunting). There appear to be no immediate direct threats to the persistence of this species on these lands. Fortunately, it often grows on steep slopes and in rock crevices that are not likely to be impacted by cattle grazing, off-road vehicles, mountain biking, or hiking activities. Perhaps the greatest threats are indirect through the consequences of short wildfire return intervals that tend to increase establishment and cover of introduced grass species such as Bromus tectorum L. (Brooks et al. 2004). We recommend that R. basalticus be placed on the Review List by the Washington Natural Heritage Program to document the abundance and distribution of this species more fully. It is possible that additional populations of R. basalticus occur on tribal and private lands within the known range of this species. Pursuing access to these lands and assessing potential threats to extant populations of R. basalticus should be part of any conservation plan developed.
Key to Sympatric Ranunculus Taxa in South-Central Washington
The key here treats native Ranunculus taxa flowering from late winter to spring that co-occur in sagebrush-steppe, low elevation grassland, and Q. garryana savannah habitats of south-central Washington and adjacent Oregon. Although there are other Ranunculus taxa that can occur in this area, none flower over a similar time period or are close in appearance to the taxa treated in the key.
1. Plants annual; achenes short-hairy on lateral faces; leaves simple, basal and lower cauline blades deeply 3-parted, segments undivided or 2 to 4-lobed, margins entire or 2–4-dentate; Whitman County, Washington, and adjacent west-central Idaho, and east end of Columbia River Gorge in Washington and Oregon, south to Baja California, Mexico R. hebecarpus Hook. & Arn.
1′ Plants perennial; achenes not short-hairy on lateral faces; leaves simple or compound
2. Leaves simple, deeply lobed to undivided; nectary scale generally sparsely ciliate on upper margin; achene beak curved or straight R. glaberrimus
3. Basal leaf blades elliptic to oblanceolate, mostly entire; stem leaves entire to 3-lobed; sagebrush and juniper scrub-land to subalpine meadows; disjunct in Olympic Mountains in Washington, otherwise occurring east of the Cascades crest from central British Columbia to northwestern California, east to the Rocky Mountains and northern Great Plains var. ellipticus (Greene) Greene
3′ Basal leaf blades mostly ovate to obovate, occasionally wider than long, more often shallowly lobed than entire; stem leaves entire or 3-lobed, lobes generally equal in size; sagebrush desert and grasslands generally at low elevations; occurring east of the Cascades crest from southern British Columbia to northwest California, east to Montana, Wyoming, and South Dakota var. glaberrimus
2′ Leaves compound; nectary scale not ciliate on upper margin; achene beak curved or straight
4. Leaves triternately dissected; leaflet lobes narrowly linear to linear, distinctly petiolulate, petiolules 6–15 mm; achene beak straight; nectary scale deeply notched; open slopes with basalt swales, oak savannah; 150–1000 m elevation; Klickitat County, Washington, to Hood River and Wasco counties, Oregon R. triternatus
4′ Leaves ternately dissected; leaflet lobes oblanceolate to ovate or obovate, generally sessile, occasionally on petiolules to 4 mm; achene beak curved to uncinate; nectary scale entire to shallowly bifid; open slopes with basalt swales, oak savannah; 300–700 m elevation; Kittitas, Yakima and Klickitat counties, Washington R. basalticus
Acknowledgments
The authors thank Peter Zika for assistance with field work, insightful discussions, and helpful comments on earlier versions of this manuscript; Ryan Garcia for field work assistance and discussions regarding Ranunculus section Epirotes and Linda Raubeson for discussions of preliminary work on R. basalticus; John Haskins for creating the distribution map; Crystal Shin for creating the botanical illustrations; and two anonymous reviewers, whose comments improved this manuscript. This work was supported by the Nygren Family Endowment for the University of Washington Herbarium at the Burke Museum, Bureau of Land Management Cooperative Agreement L20AC00236 to DEG, and the Washington Natural Heritage Program.
