Tradescantia subg. Setcreasea (K.Schum. & Sydow) M.Pell., comb. et

Pellegrini, Marco O. O., 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, pp. 11-72: 35-38

publication ID

http://dx.doi.org/10.3897/phytokeys.89.20388

persistent identifier

http://treatment.plazi.org/id/8AE7CE4A-4E9D-B4D3-ADB8-A4836DE34552

treatment provided by

PhytoKeys by Pensoft

scientific name

Tradescantia subg. Setcreasea (K.Schum. & Sydow) M.Pell., comb. et
status

stat. nov.

2.4. Tradescantia subg. Setcreasea (K.Schum. & Sydow) M.Pell., comb. et  stat. nov. Figs 6SView Figure 6, 11View Figure 11, 13View Figure 13

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. 11View Figure 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. 13 A–FView Figure 13), 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, KView Figure 13). This group was thoroughly studied and almost completely monographed by Hunt (1975), 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, KView Figure 13). Tradescantia sect. Tradescantia ser. Sillamontanae  was differentiated from T. sect. Setcreasea  by Hunt (1980) by the free petals and stamens (Fig. 13JView Figure 13), and densely lanate leaves (Fig. 13D, FView Figure 13); 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. 4AView Figure 4), 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, HView Figure 13), was originally included by Hunt (1975) 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. 13DView Figure 13) and T. sillamontana  (Fig. 13F, I, JView Figure 13) 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. 13View Figure 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) 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. 13BView Figure 13), 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  .

Kingdom

Plantae

Phylum

Tracheophyta

Class

Liliopsida

Order

Commelinales

Family

Commelinaceae

Genus

Tradescantia

Loc

Tradescantia subg. Setcreasea (K.Schum. & Sydow) M.Pell., comb. et

Pellegrini, Marco O. O. 2017
2017
Loc

Tradescantia sillamontana

Matuda 1955
1955
Loc

Neotreleasea

J.N.Rose 1903
1903
Loc

Treleasea

J.N.Rose 1899
1899
Loc

Tradescantia orchidophylla

Rose & Hemsl 1897
1897
Loc

Treleasia

Spegazzini 1896
1896
Loc

Zebrina pumila

Greene 1888
1888