Tradescantia decora W.Bull, Cat. 1892: 3. 1892.
treatment provided by
|Tradescantia decora W.Bull, Cat. 1892: 3. 1892.|
6. Tradescantia decora W.Bull, Cat. 1892: 3. 1892. Figs 18, 19
Tradescantia multibracteata M.Ferrarese et al. in Büneker et al. Phytotaxa 308 (1): 90. 2017. Holotype. BRAZIL. Rio Grande do Sul: Júlio de Castilhos, às margens do rio Toropi, próximo à antiga Usina de Quebra Dentes, fl., 26 Sep 2014, H.M. Büneker et al. 355, (HDCF!; isotype: SMDB n.v.). Syn. nov.
Tradescantia valida G. Brückn., Notizbl. Bot. Gart. Berlin–Dahlem 11: 510. 1932. Holotype. BRAZIL. Without province: s.loc., cult. in Hort. Bot. Münster /W., fl., fr., 28 Apr 1932, s.leg. s.n. (B barcode B100296487!). Syn. nov.
Neotype (designated here). BRAZIL. Rio Grande do Sul: Jaguari, ca. 12.5 km ao norte de Jaguari na BR-287 em direção a Santiago, fl., fr., Dec 2005, L.Y.S. Aona & M.C. Machado 958 (UEC 2ex barcode UEC057324!; isoneotype to be distributed to: RB!).
Herbs ca. 30-70 cm tall, with indefinite base, rupicolous, rarely terrestrial. Stems erect, succulent, little branched only at the base; internodes 1.8-7 cm long at base, distally shorter, green, sometimes with vertical reddish-purple striations, glabrous. Leaves spirally-alternate, sessile; ptyxis convolute; sheaths 0.4-3.8 cm long, light green, sometimes with vertical green or reddish-purple striations, glabrous, margin setose, with long hyaline hairs; blades 2.7-37.5 × 1.1-2.5 cm, linear elliptic to linear lanceolate to lanceolate, rarely ovate, falcate to complicate, succulent, glabrous, adaxially light to medium green, abaxially light green, rarely tinted vinaceous to completely vinaceous, turning olive-green to light brown when dry, base truncate to obtuse, margin green to vinaceous, setose at base or until the middle with long hyaline hairs, slightly revolute, apex acute to acuminate; midvein conspicuous to inconspicuous, secondary veins inconspicuous, becoming more evident on both sides when dry. Synflorescences terminal or axillar in the distal portion of the stems, composed of a solitary main florescence, 1 per leaf axis. Inflorescences (main florescences) consisting of a pedunculate 2 –3(– 5) cincinni fused back to back; peduncles 3.5-6.2 cm long, green, glabrous; basal bract inconspicuous, tubular, hyaline, glabrous; peduncle bracts absent; supernumerary bracts present, 1-3 per inflorescence, similar in shape and size to the cincinni bracts; cincinni bracts 1-3.5 × 0.3-1.2 cm, unequal to each other, lanceolate to ovate, rarely broadly ovate, spathaceous, glabrous, light green, abaxially slightly lighter, base truncate to obtuse, not saccate, margin green, setose at base or until the middle with long hyaline hairs, flat, apex acute; main florescence (4 –)6– 30-flowered; Flowers 1-1.5 cm diam.; floral buds broadly ellipsoid, apex acuminate; pedicels 0.7-2 cm long, green, glabrous, rarely sparsely glandular-pubescent, if present hairs hyaline; sepals 4.8-7.3 × 1.5-3 mm, green, without dorsal keels, glabrous, rarely sparsely pilose at the apex, when present hairs eglandular, hyaline; petals 4-8.6 × 2.7-5.4 mm, flat, white to white with pink apex to light pink; stamens with filaments 2.8-5 mm long, anthers 0.8-1 × 1-1.2 mm; ovary 1-1.7 × 1-1.3 cm, style 4-5.8 cm long; pistil longer than length the stamens. Capsules 2.8-4.2 × 1.8-3 mm. Seeds 1.1-3 × 1-1.8 mm, cleft towards the embryotega, testa grey to greyish-brown, cleft towards the embryotega, costate; hilum longer than ½ the length of the seed.
BRAZIL. Rio Grande do Sul: Jaguari, gruta linha 1, fr., 27 Dec 1985, J.N.C. Marchiori 149 (HDCF); São Martinho da Serra, Salto do Guassupi, fl., 4 Oct 2015, H.M. Büneker et al. 492 (HDCF, SMDB).
Distribution and habitat.
Tradescantia decora is endemic to the central region of Rio Grande do Sul, Brazil; in the Atlantic Forest and Pampa domains (Fig. 19). It can be found growing as rupicolous, rarely as a terrestrial, in rocky walls.
It was found in bloom and fruit in December and April.
The epithet “decora” means decorated, ornamented, making reference to this species beautiful appearance, decorated by its lush foliage.
Tradescantia decora is only known from five collections restricted to the state of Rio Grande do Sul, one of them cultivated in Berlin and without precise locality. Furthermore, its EOO and AOO are considerably narrow (ca. 672.001 km2 and ca. 16.000 km2, respectively). According to Bünecker et al. (2017), this spe cies is known to present small subpopulations, with its distribution range being extremely threatened by the construction of small hydroelectric powerplants in the next few years ( Marchiori et al. 2014). This might cause most or all known subpopulations to become extinct in the near future, since this species grows in rock walls near water bodies. Thus, in accordance with the IUCN recommendations ( IUCN 2001), T. decora should be considered as Critically Endangered [CR, A2ac+B2ab(iii, iv, v)+D1+E].
After analysing the original publication ( Bull 1892), I have concluded that, like most species described in Seed and Nursery Catalogues, T. decora was probably described based on living and cultivated material. Thus, no voucher was ever made for this name. Unfortunately, Bull (1892) does not present any kind of il lustration that might be selected as the lectotype for his name. Thus, according to The Code (McNeill et al. 2012, Art. 9.7), I designate the specimen Aona & Machado 958 (UEC barcode UEC057324) as the neotype of T. decora since it is in complete accordance with the protologue.
After analysing the protologue of T. decora ( Bull 1892), it became clear that that this name was conspecific to T. valida and T. multibracteata , due to its erect stems (Fig. 18A), spirally-alternate leaves (Fig. 18A), linear lanceolate to lanceolate leaf-blades with truncate base (Fig. 18A)) and, most importantly, all being restricted to the state of Rio Grande do Sul, Brazil (Fig. 19). Since T. decora has priority over T. valida and T. multibracteata , it should be treated as the accepted name for this species. Tradescantia decora can be easily differentiated from all remaining species of the T. crassula group by the presence of supernumerary bracts, its spathaceous and unequal cincinni bracts, its main florescence being generally composed by 2 –3(– 5) cincinni (Fig. 18A, E) and sepals not keeled with caducous hairs at the apex (Fig. 18G, H, J). It is similar to T. cerinthoides due to its sepals without dorsal keels (Fig. 18G, H, J). Nonetheless, they can be easily differentiated due to its generally linear elliptic to linear lanceolate to lanceolate leaf-blades (vs. elliptic to broadly elliptic or ovate to broadly ovate or obovate to broadly obovate, in T. cerinthoides ), glabrous with margins setose at the base or until the middle (vs. pubescent on both sides or only abaxially, rarely glabrous on both sides and ciliate margins) and pedicels and sepals glabrous or only sparsely pubescent at apex with eglandular hairs (vs. evenly densely velutine to hispid, sometimes with a mixture of glandular and eglandular hairs). Tradescantia decora is much more similar to T. crassula and T. seubertiana , due to their leaf-blades and sepal pubescence. These species can be easily differentiated by the pubescence of the margin of their leaf-sheaths (ciliate to shortly-setose in T. crassula ; glabrous in T. seubertiana ; and long-setose in T. decora ), the pubescence of their sepals (long-setose along the keels in T. crassula ; glabrous in T. seubertiana ; and glabrous or with few hairs at the apex in T. decora ) and by the shape of their floral buds (broadly ovoid T. crassula ; ellipsoid in T. seubertiana ; and ellipsoid in T. decora ).
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