Tradescantia subg. Mandonia
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Ordo: Commelinales
Familia: Commelinaceae
Name
Tradescantia (D.R.Hunt) M.Pell., comb. et stat. nov. – Wikispecies link – Pensoft Profile
- Tradescantia sect. Mandonia D.R.Hunt, Kew Bull. 35(2): 441. 1980. Type species. Tradescantia ambigua Mart. ex Schult. & Schult.f.
- Mandonia Hassk., Flora 54: 260. 1871., nom. illeg, non Mandonia Wedd., Bull. Soc. Bot. France 11: 50–51, t. 1. 1864.
- Skofitzia Hassk. & Kanitz, Oesterr. Bot. Z. 22: 147. 1872.
- Neomandonia Hutch., Fam. Fl. Pl., Monocot. 2: 57. 1934, Syn. nov. Type species. Mandonia boliviana Hassk. [≡ T. boliviana (Hassk.) J.R.Grant].
- Tradescantia sect. Parasetcreasea D.R.Hunt, Kew Bull. 30(3): 455. 1975, Syn. nov. Type species. Tradescantia andrieuxii C.B.Clarke
Description
Herbs geophytes, base definite, perennial, frequently succulent, terrestrial or rupicolous. Roots thick, tuberous. Stems erect, rarely prostrate with ascending apex, herbaceous to succulent, unbranched to little branched, rarely densely branched, rooting only at the basal nodes. Leaves sessile; spirally-alternate, rarely distichously-alternate, evenly distributed along the stem or congested at the apex of the stems; sheaths closed; blades flat to falcate and/or complicate, base symmetric or slightly asymmetric, midvein conspicuous, rarely inconspicuous, adaxially impressed, abaxially prominent, rounded, secondary veins conspicuous or inconspicuous. Synflorescences mainly axillary in the distal portion of the stems, sometimes exclusively axillary, rarely exclusively terminal, composed of a solitary main florescence. Inflorescences (main florescences) consisting of a sessile double-cincinni fused back to back, when terminal also pedunculate; inflorescence bract hyaline, tubular, inconspicuous; peduncle bracts absent; supernumerary bracts generally present, reduced, the same size as the leaves or the cincinni bracts, rarely leaf-like; cincinni bracts reduced, unequal to each other, non-saccate, conduplicate, free, not overlapping each other; bracteoles expanded, imbricate, linear-triangular to triangular, hyaline. Flowers bisexual, actinomorphic, flat or tubular, when present floral tube infundibuliform to hypocrateriform or campanulate; pedicel gibbous at apex, straight at anthesis and pre-anthesis, deflexed at post-anthesis; sepals equal, free, chartaceous, elliptic to broadly elliptic, not dorsally keeled, apex acute; petals sessile, rarely 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 free from the petals, rarely epipetalous, straight at anthesis, spirally-coiled at post-anthesis, medially sparsely bearded with moniliform hairs, 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 pubescent, locules 2-ovulate, style straight at anthesis, spirally-coiled at post-anthesis, variously colored, cylindrical at base, cylindrical to obconical at the apex, stigma truncate to capitulate or capitate to trilobate, pistil longer than the stamens. Capsules broadly oblongoid to subglobose to globose, light to medium brown when mature, 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, rarely costate, with ridges radiating from the embryotega, embryotega dorsal, conspicuous, with a prominent apicule.
Habitat, distribution and ecology
Tradescantia subg. Mandonia is widely but disjunctively distributed across the American continent, with species occurring in North America, Central America, and South America (Fig. 11). Its species are restricted to Seasonally Dry Forests (STDF) or other dry biomes across the continent, and possess well-developed tuberous roots that allow them to perennate through the dry season. Flowering seems to be triggered by the beginning of the wet season.
Included species
The subgenus includes ca. 20 species, including: Tradescantia ambigua Mart. ex Schult. & Schult.f., T. andrieuxii C.B.Clarke, T. boliviana (Hassk.) J.R.Grant, T. burchii D.R.Hunt, T. crassifolia Cav., T. exaltata D.R.Hunt, T. gentryi D.R.Hunt, T. guiengolensis Matuda, T. iridescens Lindl., T. llamasii Matuda, T. masonii Matuda, T. mcvaughii D.R.Hunt, T. murilloae Zamudio et al., T. nuevoleonensis Matuda, T. peninsularis Brandegee, T. petricola J.R.Grant, T. tepoxtlana Matuda, T. velutina Kunth & C.D.Bouché. A number of still undescribed species are being described, and should help better understand this taxonomically complex group (Pellegrini, Grant & Hunt, in prep.).
Comments
Tradescantia subg. Mandonia can be easily differentiated from the remaining subgenera due to its peculiar general morphology. It is characterized by its mainly axillary inflorescences, producing a raceme-like synflorescence, sessile main florescences (Fig. 12C–E), generally presenting supernumerary bracts, reduced cincinni bracts (rarely leaf-like in the terminal main florescences; Fig. 12F); chartaceous sepals, filaments apically spirally-coiled at post-anthesis (Fig. 12I), and style ½ time longer than the stamens, becoming spirally-coiled at post-anthesis (Fig. 12D, H–K, M). The leaves are commonly spirally-alternate and evenly distributed along the stems (Fig. 12B–D), but in few species the leaves can also be distichously-alternate or congested at the apex of the stems, forming a rosette (Fig. 12E). The architecture of the main florescence is of the double-cincinni type, although mutations seem to be much more frequent than in other subgenera. The main florescence can either be reduced to a solitary cincinnus or present more than two cincinni. Added to that, the number of cincinni bracts seems to vary greatly, although being generally hard to infer, due to great amount of reduction in the group’s inflorescence. Tubular flowers are known for few species (e.g. T. andrieuxii, T. crassifolia, and T. guiengolensis), while sympetaly is only described for T. andrieuxii. The connectives and anther sacs generally match the morphology described for Core Tradescantia (Fig. 12L), but some exceptions can be observed in some species and/or populations where anther morphology seems to be reminiscent of T. subg. Austrotradescantia, with rhomboid connectives and elliptic anther sacs. As expressed by Pellegrini et al. (2017)[1], T. subg. Mandonia is a poorly understood group with species of complex delimitation, which is highlighted by the herein presented results by the poorly resolved relationship between its species. This could be easily explained by the great vegetative plasticity within species, conserved reproductive features, and lack of focused field and taxonomic studies for this subgenus. Currently, species identification greatly relies on the species allopatric distributions, with little morphological differentiation (Pellegrini et al. 2017[1]). Further studies are surely necessary in order to better understand specific boundaries in the subgenus, and its biogeographical history.
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
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Other References
- ↑ 1.0 1.1 Pellegrini M, Forzza R, Sakuragui C (2017) Novelties in Brazilian Tradescantia L. (Commelinaceae). PhytoKeys 80: 1–31. https://doi.org/10.3897/phytokeys.80.12232
