Tradescantia L., Species Plantarum 1: 288. 1753, emend. M.Pell.

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 : 29-32

2. Tradescantia L., Species Plantarum 1: 288. 1753, emend. M.Pell. Figs 6O-T , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14

Type species.

Tradescantia virginiana L.

Description.

Herbs chamaephytes or geophytes, base definite or indefinite, perennial, frequently succulent, terrestrial, rupicolous or epiphytes. Roots thin and fibrous or thick and tuberous. Rhizomes absent. Stems prostrate with ascending apex or erect, herbaceous to succulent, rarely fibrous, unbranched to branched only at base or little to densely branched, rooting at the basal nodes or at the distal ones when they touch the substrate. Leaves sessile to subpetiolate; distichously or spirally-alternate, evenly distributed along the stem or congested at the apex of the stem; sheaths closed or split open at maturity; ptyxis involute or convolute; blades flat to falcate and/or complicate, base symmetrical or asymmetrical, midvein conspicuous or not, secondary veins conspicuous or not. Synflorescences terminal or axillary in the distal portion of the stems, sometimes exclusively axillary, composed of a solitary main florescence or a main florescence with 1-several coflorescences. Inflorescences (main florescences) consisting of a pedunculate double-cincinni fused back to back, sometimes the main florescence composed of 3(-5) cincinni fused back to back, rarely reduced to a solitary cincinnus in axillary inflorescences; inflorescence bract hyaline, tubular, inconspicuous; peduncle bracts present or not; supernumerary bracts present or not; cincinni bracts leaf-like, spathaceous, sometimes reduced (bracteose), generally differing from the leaves mostly only in size, similar to unequal to each other, saccate or not, free from each other; cincinni sessile, contracted, bracteoles inconspicuous or expanded, imbricate or completely involving the cincinnus, linear-triangular to triangular or flabellate, hyaline. Flowers bisexual, actinomorphic or slightly zygomorphic due to the unequal sepals and geniculate pedicels, chasmogamous, flat or tubular, when present floral tube infundibuliform to hypocra teriform, rarely campanulate; pedicel gibbous at apex or not, upright or geniculate at anthesis and pre-anthesis, deflexed at post-anthesis; sepals equal or unequal, free to conate, membranous or chartaceous, rarely fleshy, cucullate, dorsally keeled or not, margin hyaline, apex acute, persistent in fruit; petals sessile or clawed, equal, free to conate, blade flat or plicate; stamens 6, arranged in two series, equal or subequal, filaments free from each other, free from the petals or epipetalous, straight or spirally-coiled at anthesis and post-anthesis, bearded or not with moniliform hairs, when present hair basal or medial or apical, sparse to dense, much shorter or as long as the stamens, anthers basifixed, rimose, connective rhomboid or cordate to sagittate to linearly-tapered or quadrangular to rectangular, generally yellow, but also white or orange or red or pink or lilac, anther sacs ellipsoid or round or C-shaped, divergent, generally yellow, sometimes also white or pink or lilac, pollen generally yellow, sometimes white; ovary sessile, subglobose, white, glabrous, 3-locular, locules equal, locules (1-)2-ovulate, ovules uniseriate, style straight at anthesis, straight or spirally-coiled at post-anthesis, variously colored, obconical or cylindrical at base, cylindrical at length, conical or cylindrical to obconical at the apex, stigma punctate or truncate to capitulate or capitate to trilobate, pistil shorter or the same length or longer than stamens. Capsules subglobose to globose, light to medium brown when mature, loculicidal, 3-valved, sometimes apiculate due to persistent style base. Seeds exarillate, 1-2 per locule, reniform to ellipsoid to narrowly trigonal, ventrally flattened, cleft or not towards the embryotega, testa smooth to faintly rugose to rugose or scrobiculate or costate with ridges radiating from the embryotega, hilum linear, embryotega dorsal or semilateral, conspicuous or not, generally covered by a cream farina, with a prominent apicule or not.

Habitat, distribution and ecology.

Neotropical, ranging from southern USA to Argentina, having Mexico and Central America as its diversity center (Fig. 7 ). Tradescantia , as evidenced by its wide distribution and morphological variation, grows in a wide range of environments. The main habitat and ecological traits of the genus are discussed below, under each of the five proposed subgenera.

Phylogenetic placement and circumscription.

With the present recircumscription of Tradescantia , the genus seems to be finally monophyletic and easily morphologically characterized. Based on molecular and combined data, Tradescantia is sister to the clade composed by Gibasis + Elasis , with these three genera being sister to the clade composed by Tripogandra s.l. and all lineages of the polyphyletic Callisia (Bergamo 2003; Evans et al. 2003; Wade et al. 2006; Burns et al. 2011; Zuiderveen et al. 2011; Hertweck and Pires 2014; Pellegrini et al. in prep.). This whole clade (see Fig. 4B ) is morphologically supported by the presence of an inconspicuous, hyaline and tubular basal bract, and the main florescence reduced to a double-cincinni fused back to back. As stated in this study and thoroughly discussed by Hunt (1975, 1980, 1983, 1986b), the circumscription of Tradescantia has been the focus of great discussion since its description by Linnaeus (1753). Since the circumscription adopted in the present study does not match any of the previous circumscriptions, I propose an amendment to the description to the genus, to assure taxonomic clarity and aid taxonomists to recognize it.

Growth form and life cycle.

Despite common misconception, almost all species of Tradescantia are perennial herbs, lacking a true rhizome. In some species of Tradescantia , some portions of the stems might become non-chlorophyllate due to shading and produce shortened internodes from being underground. Nonetheless, these stems lack cataphylls and the anatomic characterization needed for them to be correctly classified as rhizomes. Thus, the only perennation structures known for the genus are the well-known tuberous roots, characteristic of T. commelinoides , T. subg, Mandonia (Fig. 12A ), T. subg. Setcreasea , and T. subg. Tradescantia (Fig. 14A ). The only truly annual species are restricted to T. subg. Tradescantia , but this character is not typical of the subgenus as a whole. Species appearing annual lack conspicuously tuberous roots and occur in the northernmost range of the genus in temperate zones, which may not be hardy during harsh and snowy winters.

Key to the subgenera of Tradescantia

1	Stems prostrate with ascending apex or erect; sepals generally all keeled, filaments densely bearded at the base with long moniliform hairs, stigma punctate; embryotega inconspicuous	Tradescantia subg. Austrotradescantia (Figs 6O , 9 )
-	Stems erect, rarely prostrate with ascending apex; sepals rarely keeled, if present keel restricted to the dorsal sepal, filaments glabrous to sparsely bearded at mid-length, rarely at the base or apex with short moniliform hairs, stigma truncate to capitulate or capitate to trilobate; embryotega with a conspicuous apicule	2
2	Roots thin and fibrous, rarely tuberous; inflorescence composed by the main florescence and generally 1-many coflorescences, peduncle bracts commonly present, cincinni bracts spathaceous; stamens subequal, connectives cordate to sagittate to linear-tapered, rarely rhomboid, anther sacs globose, rarely ellipsoid, pollen white; embryotega semilateral	Tradescantia subg. Campelia (Figs 6P-Q , 10 )
-	Roots fleshy to tuberous; inflorescence composed only by the main florescence, peduncle bracts never present, cincinni bracts leaf-like or reduced; stamens equal, connectives quadrangular to rectangular, rarely slightly rhomboid to slightly sagittate, anther sacs elliptic to curved, pollen yellow; embryotega dorsal	3
3	Main florescences sessile, mainly axillary, cincinni bracts reduced; sepals chartaceous, filaments and style spirally-coiled at post-anthesis, style ½ longer than the stamens	Tradescantia subg. Mandonia (Figs 6R , 12 )
-	Main florescences pedunculate, rarely sessile, terminal, cincinni bracts expanded and leaf-like; sepals membranous, filaments and style straight at post-anthesis, style equal or shorter than the stamens	4
4	Leaves lanceolate to ovate to rotund, rarely cylindrical, base obtuse to slightly cordate; pedicel apically gibbous, flowers tubular, stamens epipetalous, filaments glabrous or sparsely bearded, stigmatic papillae evenly distributed in the stigma	Tradescantia subg. Setcreasea (Figs 6S , 13 )
-	Leaves linear to acicular, base truncate to round; pedicels apically non-gibbous, flowers flat, stamens free, filaments densely bearded, stigmatic papillae restricted to the margins of the stigma	Tradescantia subg. Tradescantia (Figs 6T , 14 )

Figures

Figure 4. Congruence between morphological and molecular datasets. A, majority-rule tree showing the sections and series proposed by Hunt (1975, 1980, 1986 b) 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).

Figure 6. Floral morphology of subtribe Tradescantiinae s. l. A Tinantia Scheidw B Thyrsanthemum Pichon C Weldenia Schult. f. D-I Callisia Loefl. s. l.: D Cuthbertia Small E Aploleia Raf. (i. e. C. sect. Leptocallisia s. s.) F Callisia s. s. (i. e. C. sect. Callisia) G Callisia sect. Brachyphylla D. R. Hunt H Hadrodemas H. E. Moore (i. e. C. sect. Hadrodemas) I-J Tripogandra Raf. s. l.: I Callisia sect. Leptocallisia pro parte J Tripogandra s. s. K-L Elasis D. R. Hunt: K E. hirsuta (Kunth) D. R. Hunt L E. guatemalensis C. B. Clarke ex Donn. Sm.) M. Pell M Matudanthus D. R. Hunt N Gibasis Raf. O-T Tradescantia L. emend. M. Pell.: O T. subg. Austrotradescantia P-Q T. subg. Campelia R T. subg. Mandonia S T. subg. Setcreasea T T. subg. Tradescantia. A by E. Barbier, B, L, P by P. Acevedo-Rodriguez, C by S. Cross, D by D. Rankin, E by J. Amith, F, J, N-O, Q-T by M. O. O. Pellegrini, G by S. Eduardo, H by C. Willemsen, I by B. E. Hammel, K by A. Kay, and M by A. Garcia Mendoza.

Figure 7. Distribution of Tradescantia L. emend. M. Pell.

Figure 8. Distribution of Tradescantia subg. Austrotradescantia (D. R. Hunt) M. Pell. in blue, and of T. subg. Campelia (Rich.) M. Pell. in purple.

Figure 9. Tradescantia subg. Austrotradescantia (D. R. Hunt) M. Pell. A-C habit: A prostrate, mat-forming habit of T. cymbispatha C. B. Clarke B detail of a branch of T. cymbispatha, showing the distichously-alternate leaves C young specimen of T. cerinthoides Kunth, showing the rosette habit and spirally-alternate leaves D subpetiolate leaf of T. tenella Kunth E-F inflorescence: E inflorescence of T. fluminensis Vell., showing the leaf-like, saccate cincinni bracts, and deflexed pedicels at post-anthesis F synflorescence of T. umbraculifera Hand. - Mazz., showing two inflorescence per leaf axil, and spathaceous, saccate cincinni bracts G floral bud of T. fluminensis, showing three keeled sepals H-I flowers: H flower of T. fluminensis, showing the white, plicate petals I flower of T. cerinthoides, showing the pink, flat petals J anther of T. fluminensis, showing the rhomboid connective and elliptic anther sacs K style of T. fluminensis, showing the punctate stigma L seed of T. cerinthoides, showing the costate testa cleft towards the embryotega, and the inconspicuous embryotega. All photos by M. O. O. Pellegrini.

Figure 10. Tradescantia subg. Campelia (Rich.) M. Pell. A-B habit: A prostrate habit of T. zebrina Heyhn. ex Bosse, also showing the distichously-alternate, subpetiolate, striped leaves B rosette habit of T. spathacea Sw., also showing the spirally-alternate and sessile leaves C-E inflorescence: C synflorescence showing the presence of a coflorescence, also showing the berry-like fruits of T. zanonia (L.) Sw. D main florescence of T. polliae D. R. Hunt, showing the basally fused, folded, non-saccate, not overlapping, cincinni bracts and flat flower E main florescence of T. zanonia, showing the basally free, not folded, saccate, overlapping cincinni bracts, geniculate pedicels at anthesis and pre-anthesis, and the infundibuliform flower F-H flowers: F oblique view of a flower of T. zebrina G cluster of flowers of T. spathacea, showing the orange to red anther sacs H oblique view of a flower of T. commelinoides Schult. & Schult. f., showing the linearly-tapered connectives I anther of T. zanonia, showing the sagittate connective and round anther sac. J style of T. zanonia, showing the capitate stigma. A, C, E, F, I, J by M. O. O. Pellegrini, B by L. Gutierrez, D by F. A. Michelangeli, G by S. Neuwirth, and H by P. Acevedo-Rodriguez.

Figure 11. Distribution of Tradescantia subg. Mandonia (D. R. Hunt) M. Pell. in yellow, of T. subg. Setcreasea (K. Schum. & Sydow) M. Pell. in green, and Tradescantia L. subg. Tradescantia in pink.

Figure 12. Tradescantia subg. Mandonia (D. R. Hunt) M. Pell. A thick tuberous roots on T. boliviana (Hassk.) J. R. Grant. B-E habit: B vegetative shoot of T. ambigua Mart. ex Schult. & Schult. f., showing the spirally-alternate leaves C flowering shoot of T. crassifolia Cav., showing the sessile and axillary inflorescences restricted to the apex of the branch D flowering shoot of T. ambigua Mart. ex Schult. & Schult. f., showing the sessile and axillary inflorescences evenly distributed along the stem E rosette habit of T. iridescens Lindl., showing the inflorescences restricted to the apex of the stem or in lateral shoots F detail of an inflorescence of T. ambigua, with arrows indicating the reduced cincinni bracts G post-anthesis flower of T. boliviana, showing glandular-pubescent sepals and hispid immature capsule H-K flowers: H flower of T. ambigua at anthesis I flower of T. ambigua at post-anthesis, showing the spirally-coiled filaments J flower of T. boliviana at anthesis, showing the peculiarly long filaments and style; K flower of T. crassioflia at anthesis, showing the campanulate perianth L anther of T. ambigua, showing the C-shaped anther sacs and quadrangular and slightly curved connective M style of T. ambigua, showing the capitulate stigma. A, J by P. Christian (RarePlants. co. uk), B by E. O. Moura, C, K by T. R. Van Devender, D, I by L. J. Leitao, E by J. C. Garcia Morales, F, H, L-M by M. O. O. Pellegrini, and G by Instituto Darwinion.

Figure 13. Tradescantia subg. Setcreasea (K. Schum. & Sydow) M. Pell. A-D habit: A prostrate habit with ascending apex to T. buckleyi (I. M. Johnst.) D. R. Hunt B the dwarf habit of T. pygmaea D. R. Hunt C erect habit of T. hirta D. R. Hunt D habit of T. rozynskii Matuda, showing the spirally-alternate and strongly complicate leaves E-F leaves: E young leaf of T. pallida (Rose) D. R. Hunt cv. Purpurea, showing the glabrous leaves with lanate hairs at the margin F branch of T. sillamontana Matuda, showing the distichously-alternate leaves, densely covered by lanate hairs G-H inflorescence: G main florescence of T. brevifolia H inflorescence of T. hirta I post-anthesis flower of T. sillamontana, showing the hyaline sepals. J-K flowers: J front view of a flower of T. sillamonata K front view of a flower of T. pallida L anther of T. pallida, showing the quadrangular connective and C-shaped anther sacs M style of T. pallida, showing the trilobate stigma. A by J. M. Jenkins, B by M. Egger, C by J. - P. Piquet, D by J. Vich, E, I-M by M. O. O. Pellegrini, F by D. Stang, G by K. Yatskievych, and H by O. Peri.

Figure 14. Tradescantia L. subg. Tradescantia. A tuberous roots of T. ohiensis Raf. B-D habit: B erect robust habit of T. ohiensis C erect delicate habit of T. pinetorum Greene D rosette habit of T. longipes E. S. Anderson & Woodson. E, leaf-sheath split at maturity of T. ohiensis F detail of the leaf-blade of T. ohiensis, showing the conspicuous secondary veins G-H inflorescence: G inflorescence of T. ohiensis, showing the saccate cincinni bracts H inflorescence of T. virginiana L., showing the non-saccate cincinni bracts and densely pubescent bracts, pedicels and sepals I floral bud of T. ohiensis, showing the non-gibbous pedicel apex J-L flowers: J front view of a flower of T. ohiensis K front view of a flower of T. pinetorum L oblique view of a flower of T. virginiana M anther of T. ohiensis, showing the quadrangular and slightly curved connective, and the C-shaped anther sacs. N, style of T. ohiensis, showing the capitate stigma. A-B, E-F, H-I, L by G. Davidse, C, K by R. W. Van Devender, D by B. Nellums, and G, J, M-N by M. O. O. Pellegrini.