Tradescantia seubertiana M.Pell., 2016

Pellegrini, Marco Octávio De Oliveira, 2016, A new species of Tradescantia L. sect. Austrotradescantia D. R. Hunt (Commelinaceae) from Southern Brazil, Phytotaxa 265 (1), pp. 79-84 : 80-83

Tradescantia seubertiana M.Pell. , sp. nov. ( Fig. 1–2 )

Tradescantia crassulae Link & Otto (1828: 13) affinis, sed planta montana, omnino glabrata, basi foliorum obtusa vel cordata ad amplexicaule, et petalis roseis.

Type: — BRAZIL. Santa Catarina: Grão-Pará, Serra do Corvo Branco , 4 October 2014, fl., M. O. O.Pellegrini et al. 436 (holotype: RB!; isotypes: SPF!, US!).

Herbs rupicolous, ca. 20–40 cm tall. Roots thin, fibrous. Stem erect, succulent, little branched, branching at the base, rarely branching at the upper half; internodes 3.1–6.3 cm long at base, distally shorter, green to reddish-purple to vinous, glaucous, glabrous. Leaves distichously-alternate, sessile; sheaths 0.4–1.3 cm long, green to green with vinous striations to vinous, glaucous, glabrous, margin glabrous; blades ovate to broadly ovate, 2.8–7.7 × 0.9–3.2 cm, falcate to conduplicate, succulent, glabrous, adaxially light-green, glaucous, abaxially slightly lighter to reddish-purple to vinous, glaucous, turning olive-green to light-brown when dry, base obtuse to cordate to slightly amplexicaulous, rarely cuneate, margin green, entire, slightly revolute, apex acute; midvein conspicuous to inconspicuous, adaxially impressed to inconspicuous, secondary veins inconspicuous on both sides, becoming more evident on both sides when dry. Inflorescences terminal or axillar in the distal portion of the stems, composed of a solitary main florescence, 1 per leaf axis; main florescence a pedunculate double-cincinni fused back to back; peduncles 1.6–3.7 cm long, green to reddish-purple to vinous, glaucous, glabrous; cincinni bracts similar to each other, ovate to broadly ovate, 0.7–3.3 × 0.4–1.2 cm, leaf-like, glabrous, adaxially light-green, glaucous, abaxially slightly lighter to reddish-purple to vinous, glaucous, base obtuse to cordate, not saccate, margin entire, apex acute; double cincinni ca. 6–14-flowered; bracteoles inconspicuous, imbricate, linear-triangular to triangular, hyaline. Flowers bisexual, actinomorphic, flat (not forming a floral tube), ca. 0.8–1 cm diam., pedicels upright at anthesis and pre-anthesis, reflexed at post-anthesis, 0.7–1.4 cm long, green to reddish-purple to vinous, glaucous, glabrous; floral buds ellipsoid, apex acute; sepals equal, free, ovate, cucullate, margin hyaline, apex acute, persistent in fruit, 4.8–5.9 × 2.4–4.6 mm, dorsally keeled, green to reddish-purple to vinous, glaucous, glabrous; petals equal, free, elliptic to ovate, rarely broadly ovate, not-clawed (sessile), flat, 6.3–7 × 3.2–4.4 mm, light-pink to pink; stamens 6, arranged in two series, equal, filaments free from the petals and from each other, filaments 2.8–3.2 mm long, basally densely bearded with moniliform hairs, hairs as long as the stamens, white, anthers basifixed, rimose, ca. 0.5–0.8 × 1.3–1.5 mm, connective expanded, rhomboid, yellow, anther sacs ellipsoid, divergent, yellow, pollen yellow; ovary sessile, sub-globose, 1–1.3 × 0.9–1.2 cm, white, glabrous, 3- locular, locules equal, locule 2-ovulate, ovule uniseriate, style straight, white, cylindrical, conical at the apex, 4.3–8.5 cm long, pistil longer than the stamens, stigma punctate. Capsules globose, 1.8–2.6 × 1.8–2.2 cm, light-brown to brown when mature, loculicidal, 3-valved, sometimes apiculate due to persistent style base. Seeds exarillate, 1–2 per locule, 1–1.2 × 0.8–1 mm, ellipsoid to narrowly trigonal, ventrally flattened, testa grey, costate arranged in radiated ridges, hilum linear, longer than ½ the length of the seed, embryotega dorsal.

Examined material (paratypes): — BRAZIL. Paraná: Urubici , Rio dos Bugres, 11 November 2001, fl., fr., Hatschbach et al. 72640 ( MBM) ; loc. cit., Comunidade de São Pedro, 15 November 2008, fl., Silva et al. 7171 ( MBM). Rio Grande do Sul: Bagé. Km 82 da rodovia Caçapava do Sul / Bagé , 30 September 1982, fl., fr., Mattos 25637 ( HAS) ; Bento Gonçalves, na descida da Serra do Vale do Rio das Antas , 17 October 1988, fl., fr., Silveira & Mansan 6066 ( HAS) ; Pelotas , Instituto Agronômico do Sul, March 1955, fl., fr., Boeira 1188 ( HAS) ; Rio Pelotas , BR-116, km 270, 23 November 1980, fl., Krapovickas & Vanni 36870 ( CTES) ; São Francisco de Paula, Barragem Passo do Inferno , 28 November 1996, fl., fr., Mansan & Neves s.n. ( HAS 36560 ) ; loc. cit., 27 October 1997, fl., Mansan 65 ( HAS) ; Santa Maria do Herval , 1 November 1989, fl., fr., Silveira 9271 ( HAS) ; Vacaria, entre Vacaria e Caxias do Sul , 26 December 1961, fl., fr., Pereira 6527 ( RB) ; loc. cit., a 8km do Rio Pelotas , na rodovia para Lajes, s.dat., fl., fr., Mattos & Mattos 24682 ( HAS) ; loc. cit., 29 November 1986, fl., fr., Mattos & Mattos 30378 ( HAS) ; Veranópolis , 10 km S de the pink color of the petals. Photographs by M. O. O. Pellegrini .

Veranópolis, 16 September 1971, fl., Lindeman & Irgang s.n. ( CTES 202947, HAS 4953, ICN 8107); loc. cit., Estação Experimental Fitotécnica, 4 November 1982, fl., fr., Mattos & Bassan 28557 ( HAS); loc. cit., no vale do Rio das Antas, 27 September 1985, fl., Mattos & Bassan 28542 ( HAS); loc. cit., no vale do Rio das Antas, 27 September 1985, fl., Mattos & Mattos s.n. ( HAS 67967); loc. cit., no vale do Rio das Antas, na rodovia para Veranópolis, 27 October 1987, fl., fr., Mattos & Silveira 31228 ( HAS).

Etymology: —This species is named after the prominent German botanist Moritz August Seubert (1818–1878), in appreciation for his extensive contribution to Commelinaceae systematics, especially for his contributions to the knowledge of the Brazilian Commelinaceae ( Seubert 1855) and Tradescantia sect. Austrotradescantia .

Distribution, habitat and ecology: — Tradescantia seubertiana occurs in montane rainforests within the Planalto Central region, along Serra do Mar ridge, in the states of Santa Catarina and Rio Grande do Sul, Brazil ( Fig. 2 ). It can be found growing on wet rocky cliffs, from ca. 700 to 1,800 meters above the sea level, or in southern grasslands in Rio Grande do Sul, near the border to Uruguay.

Phenology: — Tradescantia seubertiana was found in bloom and in fruit from September to March.

Conservation status: — Tradescantia seubertiana is known from few localities and very small populations, none of which are inside any conservation unit. Also, this species is directly threatened by habitat loss, since all known collections are found along roads and high roads currently being enlarged. In a near future, most known subpopulations might go extinct. Thus, following the IUCN recommendations ( IUCN 2001), this species should be considered Critically Endangered [CR, A3cd;C2a(i)].

Affinities and Morphological notes: — Tradescantia seubertiana is morphologically similar to T. crassula due to its erect habit, conduplicate to falcate, succulent leaves, with inconspicuous secondary veins, cincinni bracts non-saccate, pistil longer than the stamens and hilum longer than ½ the length of the seed. It can be differentiated by its glabrous stems (vs. stems sometimes with a leaf-opposed longitudinal line of short, uniseriate, light-brown to hyaline hairs in the terminal portion of the stems), glabrous leaf-sheath margin—a very uncommon character in Commelinaceae —(vs. leaf-sheath margin ciliate to setose in T. crassula ), leaf base obtuse to cordate to slightly amplexicaulous (vs. obtuse to truncate), ellipsoid flower buds (vs. broadly ovoid), sepals glabrous (vs. setose to sparsely setose, with sparse hyaline hairs restricted to the keel), and by its light-pink to pink petals (vs. white). Additionally, T. seubertiana is found growing exclusively at wet rocky cliffs, while T. crassula is commonly found growing in open fields, sand dunes near the shore, dry rocky outcrops, in the understory as a terrestrial or, sometimes, as an epiphyte.

Tradescantia seubertiana is only superficially similar to T. certinhoides Kunth (1843: 83) due to its erect habit, succulent, conduplicate to falcate leaves, non-saccate cincinni bracts and pink petals (which can vary in T. certinhoides from white to light-pink to pink to lilac). Tradescantia certinhoides varies greatly inside the same population and most of its phenotypic plasticity has been observed at my live collection and throughout natural populations across this species’ distribution range. Tradescantia certinhoides is the only species from Tradescantia section Austrotradescantia to possess spirally-arranged leaves (that may remain spirally-arranged throughout the plant’s adult life or may become distichously-arranged with age, like the remaining species of the group), blades variously covered with velutine to hispid to glandular indumenta (normally all types of indumenta can be found in the same individual or in the same population), sepals without keels, and sepals homogeneously covered by velutine to hispid to glandular indumenta.

Tradescantia seubertiana is a member of the well-supported T. crassula morphological group recovered in the recent phylogeny for Tradescantia sect. Austrotradescantia (Pellegrini 2015) . The species from this group are characterized by possessing erect habit, conduplicate to falcate, succulent leaves, with inconspicuous secondary veins, cincinni bracts non-saccate, and for preferentially inhabiting open areas and rocky outcrops (Pellegrini 2015). I present below an identification key for the species from this group.

Figures

FIGURE 1. Tradescantia seubertiana M.Pell. A. Serra do Corvo Branco, Santa Catarina, Brazil. B. habit, showing an individual growing on a wet rocky cliff. C. habit, showing the erect stem position. D. detail of the stem, leaf-sheath and the abaxial side of the leaf-blade, showing the reddish-purple coloration and the complete absence of indumenta. E. detail of the floral buds and flowers at post-anthesis, showing the reddish-purple coloration of the pedicels and sepals, and the complete absence of indumenta. F. detail of the inflorescence, showing the not saccate cincinni bract base, and side view of the flower, showing the pistil longer than the androecium. G. flower, showing

FIGURE 2. Distribution map of Tradescantia seubertiana M.Pell.