Taxonomic notes on Lyroglossa and Pteroglossa ( Orchidaceae : Spiranthinae ) : two new generic records for the flora of Rio Grande do Sul

Lyroglossa and Pteroglossa (Orchidaceae: Spiranthinae) are first recorded for Rio Grande do Sul. Descriptions, illustrations, taxonomic notes and distribution are presented. We also provide an artificial key to distinguish the genera of the “Stenorrhynchos Clade” reported so far in Rio Grande do Sul.


INTRODUCTION
Spiranthinae Lindl.ex Meisner comprises about 42 genera and 470 species (Chase et al. 2003, Salazar 2003) of predominantly terrestrial orchids (Salazar et al. 2003).This subtribe has two main biodiversity centers, one in Mexico and Central America and the other in Southern andSoutheastern Brazil (Dressler 1993, Balogh 1982).
During fieldwork and the revision of some herbaria we verified the occurrence of two Spiranthinae genera: Lyroglossa Schltr.and Pteroglossa Schltr., currently included within the so-called "Stenorrhynchos Clade", sensu Salazar et al. (2003).To date, these taxa have not been formally cited for the orchid flora of Rio Grande do Sul (Rambo 1965, Pabst andDungs 1975).The purpose of the present contribution is thus to present descriptions, diagnostic features, illustrations, geographical and taxonomic notes for these taxa.In addition, an artificial key of the genera currently placed into the "Stenorrhynchos Clade" that are native to Rio Grande do Sul Brazilian State is provided.This paper is part of a series of taxonomic studies on the Orchidaceae native to Rio Grande do Sul (Buzatto et al. 2012(Buzatto et al. , 2014)).
Notes: Lyroglossa grisebachii is the typespecies of the genus (Salazar 2003).Lyroglossa shares some floral features with Pteroglossa, such as the short, ventrally channelled column, narrowly triangular rostellum, concave anther and marginal, completely adnate nectar glands (Salazar 2003).Based on morphological features, Salazar (2003) tentatively placed it in the so-called "Stenorrhynchos Clade".However, its relationships are still not sustained by a molecular phylogeny (Chase et al. 2003, Salazar 2003).
Distribution: Lyroglossa grisebachii is currently known in the Atlantic Rain Forest and Cerrado Biomes, in Minas Gerais, Paraná, São Paulo, Goiás, Distrito Federal and Mato Grosso.
In Rio Grande do Sul, this species dwells in wet grassy formations ("campos") surrounding TAXONOMIC NOTES FOR Lyroglossa AND Pteroglossa Herb to 45 cm high, including the inflorescence.Roots fleshy, cylindrical, often stipitate, lanuginose.Leaves ca.20-25 × 5-8 cm, 7-8, forming a basal rosette, usually present during anthesis sometimes withered, sessile, acute, coriaceous, margin translucent, light green, lanceolate, external leaves slightly attenuate at base, the inner leaves more attenuate.Inflorescence ca. 14 cm long, with ca. 15 flowers, pubescent, scape terete, partially covered by 6-7 tubular, acute bracts; raceme congested, most of them opened simultaneously; floral bracts ca.4.5-6 cm long, prominent, green, glabrous, loosely concave, ovate, acuminate.Flowers resupinate, fleshy, greenish-white with yellow veins.Sepals densely pubescent outside.Dorsal sepal ca.26 × 4 mm, slightly spreading, adherent to the lateral sepals on its proximal one-thirds, densely pubescent outside, lanceolate, acuminate, the margins entire.Lateral sepals 36 × 6 mm, forming a shortly conical, rounded, prominent spur of ca. 15 mm long, densely pubescent outside, elliptic-lanceolate, falciform, acuminate, margins entire.Petals ca.29 × 5 mm, glabrous, bearing 3 conspicuous veins, fusiform, acuminate, margins entire.Labellum ca. 30 × 9 cm, three-lobed, blade pubescent outside, glabrous near the apex, adnate at base with the lateral sepals in the spur, long-clawed and narrowly channelled below the middle; the lateral lobes semi-orbicular, the mid-lobe ovate to obovate-spatulate, acute to rounded.Column ca. 15 × 10 mm, 5 mm height, hemi-terete, stout, pubescent, the base extended into a long column foot, the membranaceous clinandrium margins are enclosed with basal portion of the anther; the anther is thick, massive, ovate, long-acute, with filament completely adnate; pollinarium 2 × 3-4 mm, 3 mm height, formed by 2 deeply bipartite, granular pollinia, narrowly clavate, with ventral-apical, oval, grey TAXONOMIC NOTES FOR Lyroglossa AND Pteroglossa  Notes: Pteroglossa macrantha is the typespecies of the genus (Salazar 2003).It is worth noticing here that leaf morphology of the specimens examined do not agree with the description provided by Salazar (2003), who described the leaves of this species as being oblanceolate and long petiolate.The specimens we studied have leaves.Salazar's description of leaves fits very well the description of two other species, namely P. roseoalba (Rchb.f)Salazar & M.W.Chase and P. glazoviana (Cogn.)Garay.However, the attenuated leaves of P. macrantha (Figure 3A-B) are considerably different from this description (see species description) and are remarkably similar to those of robust specimens of Skeptrostachys Garay.
Pteroglossa comprises about ten species distributed from Mexico to Costa Rica and from Colombia to Argentina (Salazar 2003).In Brazil, Pteroglossa occurs mainly in the Atlantic Rain Forest Biome, in the states of Minas Gerais, Paraná, São Paulo, Rio de Janeiro and Espírito Santo (Salazar 2003).It shares a number of morphological features (e.g.labellum and column shape; Figure 3D) with other members of the "Stenorrhynchos Clade", mainly with Eltroplectris Raf., and this seems to indicate a closer relationship between these and other genera in this clade.Recent molecular studies (Salazar et al. 2011) support such a relationship and have indicated that Pteroglossa is inserted within the "Stenorrhynchos Clade", and is closely related to Sacoila Raf., Mesadenella Pabst & Garay and Eltroplectris.
Distribution: Pteroglossa macrantha occurs mainly at the Cerrado Biome (especially, Goiás, Distrito Federal and Mato Grosso).After an extensive revision of the literature and the herbarium material available, this species is recorded for the first time to the State of Rio Grande do Sul.This new record makes Rio Grande do Sul the austral limit of this genus.