Siderasis spectabilis M.Pell. & Faden, 2017

Pellegrini, Marco O. O. & Faden, Robert B., 2017, Recircumscription and taxonomic revision of Siderasis, with comments on the systematics of subtribe Dichorisandrinae (Commelinaceae), PhytoKeys 83, pp. 1-41 : 26-28

5. Siderasis spectabilis M.Pell. & Faden sp. nov. Figs 2 , 10 , 11

Diagnosis.

Very distinctive due to its vining habit, distichously-alternate leaves, blades asymmetric at base, main florescence a many-branched thyrse, with alternate cincinni, flowers zygomorphic, bisexual or staminate, stamens unequal, curved upwards, sigmoid filaments, and capsules globose and shallowly foveolate. It can be differentiated from S. zorzanellii by its membranous and velutine leaves, inflorescences always terminal in the secondary branches, petals dark mauve to vinaceous, rarely light pink or white, with margins ciliate with non-moniliform hairs.

Type.

Brazil. Rio de Janeiro: Santa Maria Madalena, morro atrás do Horto Santos Lima (sede do Parque Estadual do Desengano ), fl., 19 Jan 1957, L.E. Mello-Filho 1172 (holotype: R barcode R000103716!; isotypes: RB!, SPF!, US!).

Description.

Vines ca. 0.5-3 m tall, terrestrial. Roots unknown. Rhizomes unknown. Subterraneous stems unknown. Aerial stems twining, primary stem indefinite, densely branched, internodes elongate, 2.2-6.5 cm long, green, minutely velutine on both sides, hairs hyaline to light brown; secondary branches definite, unbranched, ca. 17-25 cm long, internodes elongate, 1.1-2.3 cm long, green, minutely velutine on both sides, hairs hyaline to light brown. Leaves distichously-alternate, evenly distributed along the secondary branches, sessile; sheaths 0.7-2 cm long, green to vinaceous, minutely velutine, with a line of eglandular hairs opposite the leaf above, margins setose, hairs hyaline to light brown; subpetiole 1.1-3.3 mm long to inconspicuous, C-shaped in section, canaliculate, membranous, green to dark green, minutely velutine on both sides, hairs hyaline to light brown; blades 4.6-11.8 × 1.6-2.5 cm, linear elliptic or linear lanceolate or linear oblong, membranous, adaxially dark green to green, becoming dark brown when dry, abaxially light green to green, becoming greyish green to olive-green when dry, minutely velutine on both sides, hairs hyaline to light brown, base slightly asymmetric to asymmetric, cuneate to narrowly rounded, margins vinaceous, flat, minutely velutine, hairs hyaline to light brown, apex acuminate to caudate, straight; midvein conspicuous, impressed adaxially, prominent, obtuse abaxially, secondary veins (3-)4-5 pairs, slightly conspicuous on both sides, becoming more evident when dry. Synflorescence composed of a solitary main florescence. Main florescence (inflorescence) a pedunculate, many-branched thyrse, with alternate cincinni, terminal in the secondary branches; basal bract leaf-like, amplexicaulous to sheathing, sheaths 1.2-4.8 mm long, minutely velutine, margins of the sheaths densely setose, blades 3.9-6.7 × 0.5-1.1 cm, green to dark green, minutely velutine on both sides, base opaque, margins minutely velutine, apex acuminate to caudate, hairs hyaline to light brown; peduncle 1-1.3 cm long, green, minutely velutine, hairs hyaline to light brown; cincinni bract 3.2-10.6 × 0.8-1.2 mm, linear triangular, mauve to vinaceous, minutely velutine on both sides, base truncate, margin sparsely setose, apex acuminate to caudate, hairs hyaline to light brown; cincinni 14-17 per thyrse, 3-8-flowered, peduncles 1.4-7.2 mm long, light green to pink, minutely velutine, hairs hyaline to light brown, erect in fruit; bracteoles 1.8-2.2 × 0.8-1.2 mm, ovate to broadly ovate, flat, cream-colored densely covered with vinaceous to pinkish purple spots to completely mauve to vinaceous, minutely velutine on both sides or only along the midvein, base rounded, margin hyaline, sparsely ciliate, apex hyaline, acute to obtuse, hairs hyaline to light brown. Flowers bisexual or staminate, zygomorphic, 1-1.3 cm diameter, pedicellate; pedicel 0.5-0.7 mm long, medium to dark mauve, sparsely minutely velutine, hairs hyaline to light brown, patent and slightly elongate in fruit; floral buds 3.5-4.4 × 2.4-3.8 mm, broadly ellipsoid to broadly obovoid, vinaceous to dark vinaceous, apex truncate; sepals 4.8-5.2 × 2-2.6 mm, narrowly ovate to elliptic, cymbiform, unequal, the uppermost external, broader and shorter than the others, fleshy, vinaceous to dark vinaceous, externally sparsely minutely velutine, hairs hyaline to light brown, internally glabrous, margin hyaline, glabrous to sparsely minutely velutine, hairs hyaline, apex obtuse, slightly purple; petals 5.1-6.3 × 2.8-3.6 mm, trullate to obovate, the lowermost narrower than the others, dark mauve to vinaceous, rarely light pink or white, base cuneate, margin entire, ciliate with dark mauve, eglandular, non-moniliform, uniseriate hairs, apex obtuse to rounded; stamens 6, unequal, the anterior longer than the posterior ones, curved upwards, filaments 1.8-4.6 mm long, sigmoid, white, terminal third dark mauve, anthers 1.2-1.4 × 0.8-1 mm, anther sacs dark mauve, connectives quadrangular in the shorter stamens and rectangular in the longer, dark mauve to purple; ovary 1.7-1.9 × 1-1.4 mm, ellipsoid to broadly ellipsoid, white, velutine, hairs hyaline, style 3.2-4 mm long, curved upward at the apex, white to pink, terminal third dark mauve; stigma annular-capitate, mauve to pink, papillate. Capsules and Seeds unknown.

Specimens seen (paratypes).

BRAZIL. Rio de Janeiro: Santa Maria Madalena, morro atrás do Horto Santos Lima (sede do Parque Estadual do Desengano), fl., 19 Jan 1957, L.E. Mello-Filho 1162 (R, RB, US); fl., 19 Jan 1957, L.E. Mello-Filho 1171 (R, RB, US).

Etymology.

The epithet means "admirable, remarkable, spectacular", in allusion to its distinctive growth form, small flowers with a peculiar coloration, and the unique petal margins ciliate with non-moniliform hairs.

Distribution and habitat.

Siderasis spectabilis is confined to the type locality, in the native vegetation of the Horto Santos Lima (currently the headquarters of the Desengano State Park), in Santa Maria Madalena, state of Rio de Janeiro (Fig. 2 ). Nothing is known about this species habitat, since the original labels give no information on the area and all field expeditions to recollect this plant have been unsuccessful.

Phenology.

Since all known collections were done on the same day, S. spectabilis is only known to bloom during January. Fruits and seeds are unknown for this species.

Conservation status.

Due to the complete lack of information on the distribution, ecology and lack of any collections aside from the type specimens, according to the criteria proposed by IUCN (2001), S. spectabilis should be considered Data Deficient (DD), until new collections and data become available.

Affinities.

Siderasis spectabilis is morphologically closely related to S. zorzanellii , but S. spectabilis can be easily differentiated due to its inflorescences being always ter minal in the secondary branches (vs. axillary in the primary branches or terminal in the secondary branches, in S. zorzanellii ), and petals dark mauve to vinaceous, rarely light pink or white, and margins ciliate with non-moniliform hairs (vs. white and glabrous margins). All studied specimens were in excellent condition, and color of most organs could be easily described. Regarding color pattern in the androecium and gynoecium, S. spectabilis is similar to S. albofasciata . These are the only two species in the genus to present the upper third of filaments and style, and the anthers in the same color as the petals, contrasting greatly with the white base of filaments and style, and the white ovary of other species. Nevertheless, both species can be easily differentiated using vegetative or reproductive characters. One specimen (L.E. Mello-Filho 1171) is peculiar in being the only specimen with light-colored flowers. In the label, it is described by the collector as possessing white flowers. Nonetheless, while analyzing the duplicates available at R, RB, SPF and US, we noticed that a few flowers possessed pale pink pigment (particularly noticeable in the petals and stamens). We believe that these specimens might represent albino or semialbino individuals, and thus merit no taxonomic status, especially since they were collected at the same place and date as the remaining dark-flowered specimens.

Aona (2008), in her unpublished Ph.D. thesis, lists one of the paratypes of S. spectabilis under Dichorisandra incurva Mart. This is justified by her due to the specimens climbing habit, decumbent apical branches, distichously-alternate and sessile leaves, inflorescence composed of a pedunculate, many-branched thyrse, with alternate cincinni, and “white” [sic] flowers. Nevertheless, S. spectabilis can be easily differentiated by its erect inflorescences (vs. pendant to curved downwards, hence the name, in D. incurva ), flower buds broadly ellipsoid to broadly obovoid, with truncate apex (vs. ellipsoid, with acute apex), sepals fleshy (vs. membranous), petals dark mauve to vinaceous, rarely light pink or white, with margins ciliate with non-moniliform hairs (vs. white with glabrous margins), stamens 6, anthers dorsifixed, 3 to 4 times shorter than the filaments, dehiscent by extrorse slits, and anther sacs divergent, semicircular, and expanded connectives (vs. stamens 6 or 5 + the upper one modified into a staminode, anthers basifixed, 3 to 4 times longer than the filaments, dehiscent by introrse slits, but functionally poricidal, anthers sacs parallel, elongate, and inconspicuous connectives). All these floral characters can be easily observed with the dissection of mature flower buds in herbarium specimens. The floral morphology of D. incurva is illustrated in Fig. 1I .

Figures

Figure 1. Floral morphology of subtribe Dichorisandrinae s. l. A-C Siderasis Raf. emend M. Pell. & Faden: A S. fuscata (Lodd.) H. E. Moore B S. albofasciata M. Pell. C S. zorzanellii M. Pell. & Faden. D-L Dichorisandra J. C. Mikan: D D. acaulis Cogn. E D. hexandra (Aubl.) C. B. Clarke F D. thyrsiflora J. C. Mikan G D. paranaensis D. Maia et al. H D. nana Aona & M. C. E. Amaral I D. incurva Mart. J D. penduliflora Kunth K D. sagittata Aona & M. C. E. Amaral L D. radicalis Nees & Mart. M Cochliostema odoratissimum Lem. N Geogenanthus rhizanthus (Ule) G. Brueckn. O Plowmanianthus panamensis Faden & C. R. Hardy. Photographs A-B, D-G, J by M. O. O. Pellegrini, C by J. P. F. Zorzanelli, H by V. Bittrich, I by G. H. Shimizu, K by J. L. Costa-Lima, L by M. A. N. Coelho, M by R. Moran, N by D. Scherberich, and O by C. R. Hardy.

Figure 2. Distribution map of Siderasis Raf. emend. M. Pell. & Faden. Blue circles - S. albofasciata; Blue triangles - S. almeidae; Red circles - S. fuscata; Red triangles - S. medusoides; Blue square - S. spectabilis; Red Square - S. zorzanellii; BA - state of Bahia; ES - estate of Espirito Santo; RJ - estate of Rio de Janeiro.

Figure 10. Holotype of Siderasis spectabilis M. Pell. & Faden. Image courtesy of the Museu Nacional, Rio de Janeiro, Brazil.

Figure 11. Line drawings of Siderasis spectabilis M. Pell. & Faden. A bracteole B front view of a bisexual flower, showing the petals ciliate with non-moniliform hairs C detail of the petal margin, showing the non-moniliform hairs D lower stamen, showing the rectangular anther connective E upper stamen, showing the quadrangular anther connective F Detail of the gynoecium, showing the velutine ovary and bent style. Line drawings by M. O. O. Pellegrini.