Tradescantia subg. Setcreasea
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Ordo: Commelinales
Familia: Commelinaceae
Name
Tradescantia (K.Schum. & Sydow) M.Pell., comb. et stat. nov. – Wikispecies link – Pensoft Profile
- Tradescantia sect. Setcreasea (K.Schum. & Sydow) D.R.Hunt, Kew Bull. 30(3): 448. 1975.
- Neotreleasea Rose, Contr. U.S. Natl. Herb. 8: 5. 1903, nom. superfluous.
- Setcreasea K.Schum. & Sydow, Just’s Bot. Jahresber. 27(1): 452. 1901.
- Treleasea Rose, Contr. U.S. Natl. Herb. 5: 207. 1899, nom. illeg., non Treleasia Speg., Revista Fac. Agron. Univ. Nac. La Plata 2: 235. 1896. Type species. Tradescantia leiandra var. brevifolia Torr. [≡ T. brevifolia (Torr.) Rose]
- Tradescantia sect. Separotheca (Waterf.) D.R.Hunt, Kew Bull. 30(3): 454. 1975.
- Separotheca Waterf., Rhodora 61: 138. 1959, Syn. nov. Type species. Zebrina pumila Greene (≡ T. pygmaea D.R.Hunt).
- Tradescantia sect. Tradescantia ser. Sillamontanae D.R.Hunt, Kew Bull. 35(2): 440. 1980, Syn. nov. Type species. Tradescantia sillamontana Matuda
- Tradescantia sect. Tradescantia ser. Orchidophyllae D.R.Hunt, Kew Bull. 35(2): 441. 1980, Syn. nov. Type species. Tradescantia orchidophylla Rose & Hemsl.
Description
Herbs geophytes, base definite, perennial, succulent, terrestrial or rupicolous. Roots thick, tuberous. Stems erect, sometimes prostrate with ascending apex, succulent, little branched to densely branched, rarely unbranched, rooting at the basal nodes, sometimes rooting at the distal ones when they touch the substrate. Leaves sessile; spirally-alternate, rarely distichously-alternate, evenly distributed along the stem or congested at the apex of the stems; sheaths closed; blades falcate and/or complicate, base symmetric, midvein conspicuous to inconspicuous, adaxially impressed, abaxially prominent, rounded, secondary veins conspicuous or inconspicuous. Synflorescences terminal in the distal portion of the stems, composed of a solitary main florescence. Inflorescences (main florescences) consisting of a pedunculate double-cincinni fused back to back; inflorescence bract hyaline, tubular, inconspicuous; peduncle bracts absent; supernumerary bracts absent; cincinni bracts leaf-like, unequal to each other, saccate, conduplicate, free, overlapping each other; bracteoles expanded, imbricate or completely involving the cincinnus, linear-triangular to triangular or flabellate, hyaline. Flowers bisexual, actinomorphic, tubular, floral tube infundibuliform to hypocrateriform or campanulate; pedicel gibbous at apex, straight at anthesis and pre-anthesis, deflexed at post-anthesis; sepals equal, free, membranous, elliptic to broadly elliptic, not dorsally keeled, apex acute; petals sessile or clawed, equal, free to conate, blade elliptic to ovate to broadly ovate or rhomboid to broadly obovoid to obovoid, flat, base cuneate to obtuse, margin entire, apex acute to obtuse; stamens 6, arranged in two series, equal, filaments epipetalous, straight at anthesis and post-anthesis, glabrous to medially sparsely bearded with moniliform hairs, when present hairs shorter than the stamens, variously colored, anthers with connective quadrangular to rectangular, rarely rhomboid, yellow, anther sacs C-shaped, rarely ellipsoid, yellow, pollen yellow; ovary glabrous or pubescent, locules 2-ovulate, style straight at anthesis and post-anthesis, variously colored, cylindrical at base, cylindrical to obconical at the apex, stigma capitate to trilobate, pistil the same length as the stamens. Capsules subglobose to globose, light to medium brown when mature, glabrous or pubescent, loculicidal, 3-valved, sometimes apiculate due to persistent style base. Seeds exarillate, 1–2 per locule, ellipsoid to narrowly trigonal, ventrally flattened, not cleft towards the embryotega, testa scrobiculate to rugose, with ridges radiating from the embryotega, embryotega dorsal, conspicuous, with a prominent apicule.
Habitat, distribution and ecology
Tradescantia subg. Setcreasea is restricted to southern USA and Mexico (Fig. 11). Its species are generally related to rocky outcrops and open dry areas. This is reflected in its species with tuberous roots and succulent vegetative organs.
Included species
This subgenus is composed by 10 species: Tradescantia brevifolia (Torr.) Rose, T. buckleyi (I.M.Johnst.) D.R.Hunt, T. hirta D.R.Hunt, T. leiandra Torr., T. mirandae Matuda, T. orchidophylla Rose & Hemsl., T. pallida (Rose) D.R.Hunt, T. pygmaea D.R.Hunt, T. rozynskii Matuda, and T. sillamontana Matuda.
Comments
Tradescantia subg. Setcreasea comprises succulent plants with complicate leaves (Fig. 13A–F), tubular flowers (generally sympetalous and epipetalous; Fig13D, G–H, J–K) and filaments that range from glabrous to sparsely barbate with short moniliform hairs (Fig. 13H, J, K). This group was thoroughly studied and almost completely monographed by Hunt (1975)[1], with only four of its currently accepted species not included in the key. Its morphology is considerably homogeneous, with species related with the commonly cultivated T. pallida forming a species complex (Fig. 13A, E, G, K). Tradescantia sect. Tradescantia ser. Sillamontanae was differentiated from T. sect. Setcreasea by Hunt (1980)[2] by the free petals and stamens (Fig. 13J), and densely lanate leaves (Fig. 13D, F); while T. sect. Tradescantia ser. Orchidophyllae was differentiated by its free petals and stamens, and generally rotund leaves congested in a rosette. Nevertheless, these two groups share all the diagnostic features of T. subg. Setcreasea (i.e. tubular flowers, pedicel the same length as the floral buds, hyaline sepals, fused and clawed petals, and epipetalous stamens), and there seems to be no good reason for treating them as separate groups inside T. subg. Setcreasea. Furthermore, in the majority rule topology (Fig. 4A), these species are nested deep within T. subg. Setcreasea and there is no way to recognize them as separate groups, without creating other non-monophyletic groups inside the subgenus. The peculiar-looking T. hirta (Fig. 13C, H), was originally included by Hunt (1975)[1] in his T. sect. Setcreasea, and is morphologically very similar to T. mirandae, differing primarily in leaf shape and androecium morphology. Furthermore, T. rozynskii (Fig. 13D) and T. sillamontana (Fig. 13F, I, J) can only be differentiated from the T. pallida species complex due to their lanate indumentum covering the entire leaf-blade, and lack of clawed petals. Aside from that, these plants are morphologically very similar (see Fig. 13). Tradescantia orchidophylla is the morphologically most discrepant species in the subgenus, due to its wide leaf-blades and very long pedicels. Nonetheless, this morphology could be easily explained as a return to understory environments. Despite being placed by Hunt (1975)[1] in a separate section, T. pygmaea is undeniably similar to the species from the T. pallida species complex. Besides the obvious stature difference (hence the species’ name; Fig. 13B), and the thicker tuberous roots, the only marking morphological difference between it and the species from the T. pallida complex is the shape of the connectives and anthers sacs that are sagittate and elliptic, similar to the ones of T. mirandae.
Taxon Treatment
- Pellegrini, M; 2017: Morphological phylogeny of Tradescantia L. (Commelinaceae) sheds light on a new infrageneric classification for the genus and novelties on the systematics of subtribe Tradescantiinae PhytoKeys, (89): 11-72. doi
Images
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![Figure 4. Congruence between morphological and molecular datasets. A, majority-rule tree showing the sections and series proposed by Hunt (1975[1], 1980[2], 1986b[3]) color-coded; the five newly proposed subgenera are represented by the black bars; Tradescantia guatemalensis C.B.Clarke ex Donn.Sm. is depicted in red, to highlight its placement as sister to Elasis hirsuta (Kunth) D.R.Hunt; the ● represents Tradescantia s.s.; Bremer Index support values are depicted over the branches, while bootstrap support values are depicted under the branches B simplification of the current hypothesis for phylogenetic relationships in tribe Tradescantieae, based on molecular data. Thyrsanthemum Pichon and Weldenia Schult.f. are depicted in red since they were not sampled in the present study. Modified from Hertweck and Pires (2014)[4].](/wiki/File:Phytokeys-89-011-g004.jpg)
Other References
- ↑ 1.0 1.1 1.2 1.3 Hunt D (1975) The reunion of Setcreasea and Separotheca with Tradescantia. In: American Commelinaceae, Vol. I. Kew Bull. 30(3): 443–458. https://doi.org/10.2307/4103068
- ↑ 2.0 2.1 Hunt D (1980) Sections and series in Tradescantia. In: American Commelinaceae, vol. IX. Kew Bull. 35(2): 437–422. https://doi.org/10.2307/4114596
- ↑ Hunt D (1986b) Campelia, Rhoeo and Zebrina united with Tradescantia. In: American Commelinaceae, vol. XIII. Kew Bull. 41(2): 401–405. https://doi.org/10.2307/4102948
- ↑ Hertweck K, Pires J (2014) Systematics and evolution of inflorescence structure in the Tradescantia alliance (Commelinaceae). Systematic Botany 39(1): 105–116. https://doi.org/10.1600/036364414X677991
