Spiranthes, Pace, Matthew C. & Cameron, Kenneth M., 2017

Pace, Matthew C. & Cameron, Kenneth M., 2017, The Systematics of the Spiranthes cernua Species Complex (Orchidaceae): Untangling the Gordian Knot, Systematic Botany (Basel, Switzerland) 42 (4), pp. 1-30 : 20-21

Spiranthes 3 kapnosperia M.C. Pace, nothosp. nov. [ Spiranthes cernua 3 Spiranthes ochroleuca ]—TYPE: U. S. A. North Carolina: Transylvania County, Great Smoky Mountains, Pisgah National Forest, ca 7.5 km NW of Balsam Grove, north side of 215, below a steep seeping cliff, growing in moss and lichen hummocks, collected 2 October 2016, Pace 1030 (Holotype: NY; isotypes: NCU, US).

Spiranthes 3 kapnosperia is most similar to S. cernua s. s. and S. ochroleuca . It can be distinguished from S. cernua s. s. by smaller, less widely gapping ivory-colored flowers, and spherical glands on the abaxial labellum surface; it can be distinguished from S. ochroleuca by its pale-yellow colored abaxial labellum surface (vs. deep golden yellow) and sepal apices that are acuminate vs. linear-lanceolate.

Terrestrial, acaulescent, deciduous herb, to ca. 30 cm tall. Roots fasciculate, fleshy, slender. Leaves 1–2, basal, held upright, remaining until after anthesis, withering shortly thereafter, linear-lanceolate to lanceolate, to 133 mm long, 8.5–10.5 mm wide, narrowly acuminate; leaf base narrowly tapered and decurrent. Peduncle glabrous, to 30 cm, 1–2 small leafy cauline bracts occasionally present, quickly reducing to adpressed, clasping, lanceolate, acute bracts; spike a single row of flowers in an open to moderately tightly coiled spiral (appearing as single rank), moderately to densely pubescent with blunt-tipped septate trichomes to 0.5 mm long. Floral bracts pubescent, broadly lanceolate, acuminate, concave around the ovary, 11.4–13.7 mm long. Flowers resupinate, campanulate, only slight gapping, slightly ascending to slightly nodding, pale ivory to white. Sepals free, moderately to densely pubescent with blunt-tipped capitate septate trichomes. Dorsal sepal slightly convex, slightly to moderately recurved near the tip, lanceolate, acuminate, 7.7–10.2 mm long, 1.6–3.3 mm wide when flattened. Lateral sepals lanceolate, acute, straight to just barely falcate, angled slightly outward and upward, the tips often surpassing the dorsal sepal and petals, 7.6–10 mm long, 1–1.9 mm wide. Dorsal petals slightly concave, lanceolate, bluntly acute, slightly to moderately recurved at tips, 7.4–10 mm long, 1.5–2.3 mm wide when flattened. Labellum shortly clawed, free but clasping the column, keeled/concave for its length, recurved strongly downward at about 2/3 the distance from the claw to labellum apex, centrally glabrous, margin entire to very slightly undulating from the base until the area of recurvature, below point of recurvature margin becoming shallowly ruffled, margin white, central area of labellum yellowish, labellum 9–9.5 mm long, 4.7–4.9 mm wide below callosities, 3.6–4 mm wide at the area of recurvature when flattened, 4.4–4.6 mm wide at widest point below recurvature; 2 basal callosities/nectar glands, conical, upright, 0.6–1 mm tall, with long, dense papillae at the base. Column protandrous, slightly rhombic, green, with a fringe of minute glands or papillae in a thin crescent just below the stigmatic surface, with a pair of upright flaps or wings at each side and clasping the column, the wings green basally; column foot glabrous; rostellum well-developed, white to ivory, tapering to thin acute membranes at the apex; stigmatic surface glabrous, shiny; anther brown, triangular-ovoid; pollinium attached to a well-developed viscidium; viscidium linear, immersed in the rostellum, leaving behind a narrow V-shaped rostellar remnant after removal. Ovary moderately to densely pubescent with septate trichomes. Fruit a light brown ovoid capsule. Figures 3 and 16 .

Etymology —From the Greek, ‘ kapnosperia ’ is a combination of ‘ KAPnó§ ’ (smoke) and ‘ SPEίRA ’ (spiral), referring to the greater Smoky Mountain region which is the endemic home of this rare hybrid. The choice of Greek (vs. Latin) is an allusion to the Greek-derived specific epithet of S. ochroleuca . A suggested common name is “Smoky ladies’ tresses”.

Spiranthes cernua s. l. and S. ochroleuca have long been hypothesized to hybridize or engage in some level of geneflow, particularly in New York and New England ( Sheviak 1982; Sheviak and Brown 2002). A binomial for this crossing, however, was never formally proposed. Based on the research we present here, S. cernua s. s. and S. ochroleuca do not share an overlapping distribution in much of New York and New England, and thus hybridization is unlikely. Hybrid plants, now described as S. 3 kapnosperia ( Figs. 3 and 16 ), do occur along creeks, wet roadsides, and wet grassy openings in a small area of their shared range in the Southern Appalachian Highlands and greater Smoky Mountains of North and South Carolina ( Fig. 14 ). The question of why this hybrid is so geographically limited compared to its parental species’ shared distribution is similar to the situation in S. niklasii , and is deserving of continued research. The designation of S. 3 kapnosperia as a nothospecies, indicated by the use of “3”, as opposed to a species of hybrid origin (such as S. incurva or S. niklasii ) is twofold: 1) S. 3 kapnosperia does not possess any unique molecular or morphological features based on the data we have collected vs. S. cernua s. s. or S. ochroleuca ; 2) S. 3 kapnosperia is nearly always found with one or both parental species (primarily S. cernua s. s.), indicating that it may still be continually formed by ongoing hybridization and introgression, and has not yet coalesced into an independent, self-perpetuating lineage (i.e. species).

Figures

FIG. 3. A. Spiranthes casei, Michigan; photo: Aaron Strouse, used with permission. B–C. Spiranthes ochroleuca, Rutland Co., Vermont. C. Characteristic ochroleucous-yellow coloration on abaxial labellum surface. D. Spiranthes ovalis var. erostellata Catling, Waukesha Co., Wisconsin, sample so2. E. Spiranthes niklasii, Yell Co., Arkansas (type location). F. Spiranthes 3kapnosperia, Transylvania Co., North Carolina (type location).

FIG.16. Spiranthes 3kapnosperia. A. Habit. B. Inflorescence. C. Flower and floral bract in profile. D–G. Flower, dissected view. D. Dorsal sepal. E. Dorsal petal. F. Lateral sepal. G. Labellum. H. Labellum, column, and ovary in natural position, with detail of spherical abaxial labellum glands. I–K. Column. I. Dorsal and ventral views. J. Profile. K. Anther. L. Pollinia. Drawn from Pace 1024 and Pace 1030 by Bobbi Angell.

FIG.14. Distribution maps of the S. cernua species complex s. s., based on herbarium specimens and phylogenetic sampling.A.S. arcisepala, S. cernua s. s., S. incurva, S. 3kapnosperia, S. niklasii. B. S. casei and S. ochroleuca. Maps produced by Elizabeth Kiernan, New York Botanical Garden GIS Lab.