Sabulina sororia B.S.Legler, 2017

Legler, Ben S. & Dillenberger, Markus S., 2017, Two new species of Sabulina (Caryophyllaceae) from Washington State, U. S. A., PhytoKeys 81, pp. 79-102 : 86-92

Sabulina sororia B.S.Legler sp. nov. Figs 2F -I , 4

Type.

U.S.A. Washington, Whatcom Co.: Mt. Baker-Snoqualmie National Forest, on west side of ridge along Sisters Divide 0.45 air km southeast of outlet of Lake Wiseman , Twin Sisters Range , 1414 m, 48.707131°N, 121.934086°W, 6 Aug 2016, B.S. Legler 14263 (holotype: WTU!; isotypes: MICH!, MO!, NY!, UBC!) .

Diagnosis.

Differs from all other glabrous, perennial Sabulina species in North America by the combination of 1-veined dried leaves, flowers partly in 2-3-flowered cymes, sepals mostly <2.5 mm long, petals conspicuously longer than the sepals, capsules 1.8-2.6 mm long and mostly> sepals, and reddish-black seeds 0.6-0.8 mm long.

Description.

Plants perennial, forming loose to dense mats 2-20 cm in diameter, glabrous throughout. Taproot slender to slightly thickened, 1-3 mm diameter near summit. Stems numerous, radially spreading from the taproot, prolifically branching; older stems decumbent to ascending, 1-10 cm, brown to tan; new shoots arising from axillary fascicles on previous year’s stems, ascending to erect, 1-4 cm, internodes of flowering shoots 0.3-2(-3) times as long as leaves, deep green or purplish. Leaves slightly to strongly overlapping or well-spaced, connate proximally to form a tight, scarious sheath; blade 1.2-3.5(-5) × 0.4-0.7 mm, ascending to spreading-ascending, straight to slightly incurved or slightly recurved, green to deep green, often maroon-tinged, shiny, subulate, rounded abaxially, nearly flat adaxially, veins not visible in life, margins rounded, not scarious, smooth, apex obtuse to rounded, usually maroon; axillary fascicles of leaves usually present; previous year’s leaves loosely marcescent on older stems, with only the midvein visible and persisting (no lateral veins). Inflorescences terminal, 2-3-flowered, open cymes, usually mixed with solitary terminal flowers; bracts 0.7-1.6 mm, lanceolate to ovate-lanceolate, incurved, green or maroon with scarious margins, rounded abaxially, flat to concave adaxially, apex obtuse to bluntly acute. Pedicels (1-)2-8(-15) mm, glabrous. Flowers perfect or functionally male or functionally female, most plants functionally monoecious to nearly dioecious. Hypanthium obscure, disc-shaped. Sepals spreading-ascending at anthesis, deep green, often lightly maroon-tinged, glabrous, broadly ovate to ovate-lanceolate, (1.4-)1.7-2.5(-3) × 0.6-1.1(-1.3) mm, 1.5-2.5(-3.5) times as long as wide, scarious margins ca. 0.05-0.15 mm wide, base cupped, apex green to maroon, acute, outer surface convex, smooth to very weakly 3-veined at anthesis, becoming 3-veined in fruit or when dried. Petals white, spreading, broadly oblong to obovate, 3.2-4(-5.2) × 1.2-2(-2.6) mm, 1.3-2(-2.5) times as long as sepals, base gradually tapered to a short, greenish-yellow claw, apex rounded to weakly truncate. Nectaries 5, at base of outer stamens, greenish-yellow, ca. 0.3-0.4 mm, truncate, alternate with the petals. Stamens 10, in 2 series of 5, either all fertile or all abortive; filaments subulate, whitish-green; anthers orbiculate, pale yellow; fertile stamens with filaments 1.5-2.8 mm and anthers (0.3-)0.4-0.5 mm; abortive stamens with filaments 0.2-0.6 mm and anthers 0.1-0.3 mm. Ovary superior; placentation shortly free-central; ovules usually 12 per ovary. Styles 3, distinct, erect to ascending; functionally male flowers with styles 0.6-0.9 mm and stigmas scarcely developed; functionally female flowers with styles 1.1-2.1 mm and stigmas linear, glandular-puberulent adaxially. Capsules light green to greenish-tan (valve margins tan), on stipe ca. 0.1-0.2 mm, ovoid-conical, 1.8-2.6 × 1.1-1.8 mm slightly longer than (rarely slightly shorter than) and mostly enclosed by the appressed sepals and withering-persistent petals, dehiscing in upper half by 3 valves, these becoming incurved on margins and slightly recurved at tip. Seeds apparently 8 per capsule, 0.7-0.8 mm, reddish-black, obliquely reniform with radicle prolonged into a curved bump, somewhat compressed, surfaces sculpted with low bumps at> 10 × magnification.

Additional specimens examined.

U.S.A. Washington, Whatcom Co.: Twin Sisters Range, 11 Aug 1939, W.C. Muenscher 10281 (WTU); Twin Sisters Range, 12 Aug 1939, W.C. Muenscher 10306 (WTU); Head of Orsina Creek , at west base of Twin Sisters Mountain , 4900 ft, T37N R6E S11, 12 Jul 1961, A.R. Kruckeberg 5225 (WTU); Northwest slope of Twin Sisters , ca. 6200 ft, 28 Jul 1968, R.J. Taylor 2158 (WWB); Crest of ridge along Sisters Divide 0.7 air km southeast of outlet of Lake Wiseman , Twin Sisters Range , 48.704998°N, 121.931408°W; 1508 m, 7 Aug 2016, B.S. Legler 14268 (ID, US, WTU) .

Etymology.

The epithet sororia is from the Latin word sororis, sister, in reference to the Twin Sisters Range.

Vernacular name.

Twin Sisters sandwort.

Distribution and ecology.

Sabulina sororia is known only from the Twin Sisters Range on the western flank of the Cascade Mountains in Whatcom County, Washington, U.S.A. (Fig. 6D ). The Twin Sisters Range consists of a large body of relatively unaltered dunite rock aproximately 16 km long by 6.5 km wide ( Tabor et al. 2003) oriented in a northwest to southeast direction, with a maximum elevation of 2135 meters and sustained ridgeline elevations above 1500 meters. The dunite rock likely formed in the earth’s mantle and was subsequently uplifted along a series of nearly vertical thrust faults ( Ragan 1963); it is a dense, crystalline, ultramafic rock composed mostly of olivine with lesser amounts of chromite and pyroxenite, rich in magnesium, iron, chromium and nickel ( Ragan 1963, Onyeagocha 1978). The rock weathers to a distinctive light reddish-brown color with a coarse-grained surface. Ultramafic rocks display a pronounced effect on the overlying vegetation ( Kruckeberg 2002, and references therein), and the Twin Sisters dunite is no exception with its depressed treeline and sparse vegetation cover above treeline.

Sabulina sororia is apparently restricted to rocky or gravelly, sparsely vegetated, subalpine and alpine slopes. Documented elevations range from 1490 to 1890 meters. Habitat information from older herbarium specimens is sparse, indicating only a "west-facing alpine ridgeline" (Grable 5023), "moist, gravelly, serpentine soil on an alpine slope" (Taylor 2158), "along streambank" (Muenscher 10281), and "olivine in massive fell-fields and talus, with krummholz lodgepole pine and subalpine fir in snow-melt basin" (Kruckeberg 5225). At the two sites visited by B. Legler in August 2016, S. sororia was observed growing most frequently in mesic, coarse, gravelly and rocky soil derived from dunite on erosional surfaces with slopes ranging from flat to ca. 30° (Fig. 5D-F ). A few plants were found in exposed crevices of stable dunite rock outcrops along a narrow ridgeline with slopes of ca. 45-60°. The species apparently avoids areas with late-lying snow. Sabulina sororia occurs as scattered individuals, forming a minor component of the sparse, low vegetation cover. Total vegetation cover of all plant species at these two sites is estimated at 5-20%. Average precipitation for the higher elevations of the Twin Sisters Range is estimated at ca. 180-190 cm per year, with about 30% of the total precipitation falling during May-September ( PRISM 2017).

Directly associated species consist of scattered tufts or mats of Carex spectabilis Dewey, Cassiope mertensiana (Bong.) G. Don, Cerastium arvense L. subsp. strictum Gaudin, Cryptogramma acrostichoides R. Br., Danthonia intermedia Vasey, Erigeron aureus Greene, Polystichum lemmonii Underw., Sabulina rubella (Wahlenb.) Dillenb. & Kadereit, Saxifraga cespitosa L., Sibbaldia procumbens L., Silene acaulis (L.) Jacq., and Smelowskia ovalis Rydb. Trees and taller shrubs are absent from these sites, though adjacent ridgelines and slopes hold patches of Abies lasiocarpa (Hook.) Nutt., Callitropsis nootkatensis (D. Don) D.P. Little, Pinus contorta Douglas ex Loudon var. latifolia Engelm., Tsuga mertensiana (Bong.) Carrière, Juniperus communis L. var. kelleyi R.P. Adams, and Phyllodoce empetriformis (Sm.) D. Don. Crustose lichens are sparse, and bryophytes nearly absent.

The southern terminus of the Twin Sisters Range extends slightly into adjacent Skagit County, and 6 km farther to the southeast of this are two smaller dunite bodies exposed at slightly lower elevation ( Tabor et al. 2003). An examination of aerial imagery suggests marginally suitable habitat for Sabulina sororia may occur in these areas, though no surveys have been conducted to determine its presence. It seems unlikely that S. sororia will be found elsewhere in the Cascades Mountains or over non-dunite rocks; however, small, subalpine exposures of ultramaphic rocks in Skagit and Snohomish counties may warrant investigation.

Phenology.

Specimens indicate the flowering period for Sabulina sororia extends from mid July to mid August, and fruiting period from early to mid August. The full ranges of flowering and fruiting periods likely vary based on timing of snowmelt and site exposure.

Conservation status.

Although apparently restricted to the Twin Sisters Range, Sabulina sororia may occur in suitable microsites throughout the upper elevations of the range within an extent of occurrence estimated at ca. 16 km2. The total number of plants cannot be estimated due to inadequate sampling across the range, possibly preventing assignment of a formal conservation status at this time. The Twin Sisters Range lies almost fully within the Mt. Baker-Snoqualmie National Forest, and the entire northeastern slope of the range lies within the Mt. Baker Wilderness. No roads or trails penetrate the range, resource extraction is absent from the higher elevations, and very few people visit each year due to difficulty of access. Direct anthropogenic impacts are therefore assumed to be very minimal.

Figures

Figure 2. Line drawings of Sabulina basaltica and Sabulina sororia. A-E. Sabulina basaltica. A Habit B Dried leaf with 3 veins C Cymose, bracteate inflorescence with two flowers D Capsule with dried, 3 - veined sepals (with sepals pushed outwards and withered petals removed to reveal capsule) E Seed F-I Sabulina sororia F Habit G Dried leaf with 1 vein H Flower I Capsule with dried, 3 - veined sepals (withered petals removed).

Figure 4. Sabulina sororia. A Plant forming a loose mat (Legler 14263) B Excavated plant with loosely sprawling stems (Legler 14268) C Fresh leaves and persisting, 1 - veined, dead leaves (Legler 14263) D Excavated plant (Legler 14263) E-F Cymose inflorescences (Legler 14263) G Dried, 1 - veined leaves (Legler 14263) H Dead leaves with only midvein persisting (Legler 14263) I Ovate-lanceolate, purple-tinged sepals (Legler 14263) J Sepals and petals, showing shapes and relative lengths (Legler 14263) K-L Flowers with different combinations of stamen and style lengths (Legler 14263) M Dried flower with dehisced capsule longer than sepals (Legler 14263) N Seeds (Legler 14263). Black scale bars are 1 mm.

Figure 5. Representative habitats. A-C Sabulina basaltica habitat A Basalt slope near the type locality (Legler 14177) B-C Plants in crevices of basalt rock faces (Legler 14177, Legler 14183) D-F Sabulina sororia habitat D Reddish-colored dunite slope at the type locality (Legler 14263) E-F Plants among dunite rock and gravel (Legler 14263, Legler 14268).

Figure 6. Distribution of Sabulina basaltica and S. sororia. A-B Reference maps of western North America and Washington State, indicating locations of inset maps C Known locations for Sabulina basaltica (open black circles) within the northeastern Olympic Mountains; gray shading indicates the predicted extent of potential habitat based on exposures of oceanic basalt rocks at subalpine to alpine elevations D Known locations for Sabulina sororia (open black squares) within the Twin Sisters Range; gray shading indicates the predicted extent of potential habitat based on exposures of dunite rock away from large snowfields at subalpine to alpine elevations.