Tradescantia subg. Mandonia (D.R.Hunt) 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: 34

publication ID

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

persistent identifier

http://treatment.plazi.org/id/010E88DF-3ADE-C884-4DF7-0296E9B884B7

treatment provided by

PhytoKeys by Pensoft

scientific name

Tradescantia subg. Mandonia (D.R.Hunt) M.Pell., comb. et
status

stat. nov.

2.3. Tradescantia subg. Mandonia (D.R.Hunt) M.Pell., comb. et  stat. nov. Figs 6RView Figure 6, 11View Figure 11, 12View Figure 12

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. 11View Figure 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. 12 C–EView Figure 12), generally presenting supernumerary bracts, reduced cincinni bracts (rarely leaf-like in the terminal main florescences; Fig. 12FView Figure 12); chartaceous sepals, filaments apically spirally-coiled at post-anthesis (Fig. 12IView Figure 12), and style ½ time longer than the stamens, becoming spirally-coiled at post-anthesis (Fig. 12D, H–K, MView Figure 12). The leaves are commonly spirally-alternate and evenly distributed along the stems (Fig. 12 B–DView Figure 12), but in few species the leaves can also be distichously-alternate or congested at the apex of the stems, forming a rosette (Fig. 12EView Figure 12). 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. 12LView Figure 12), 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), 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). Further studies are surely necessary in order to better understand specific boundaries in the subgenus, and its biogeographical history.

Kingdom

Plantae

Phylum

Tracheophyta

Class

Liliopsida

Order

Commelinales

Family

Commelinaceae

Genus

Tradescantia

Loc

Tradescantia subg. Mandonia (D.R.Hunt) M.Pell., comb. et

Pellegrini, Marco O. O. 2017
2017
Loc

Neomandonia

Hutchinson 1934
1934
Loc

Tradescantia andrieuxii

C. B. Clarke 1881
1881
Loc

Skofitzia

Hasskarl & Kanitz 1872
1872