Tradescantia hertweckii M.Pell., 2018

Pellegrini, Marco O. O., 2018, Wandering throughout South America: Taxonomic revision of Tradescantia subg. Austrotradescantia (D. R. Hunt) M. Pell. (Commelinaceae), PhytoKeys 104, pp. 1-97 : 29-32

8. Tradescantia hertweckii M.Pell. sp. nov. Figs 22 , 23

Diagnosis.

Similar to T. fluminensis due to its indefinite base, stems prostrate with ascending apex, involute ptyxis, leaf-blades with conspicuous secondary veins, saccate cincinni bracts, ovoid floral buds, keeled sepals, pistil the same length as the stamens and seeds with costate testa. It can be differentiated by its sessile leaves, blades hispid, margins ciliate, but setose at base, sepals setose along the keel, petals flat and hilum longer than ½ the length of the seed.

Type.

BRAZIL. Rio de Janeiro: Paraty, estrada para o Pico do Coriscao , próximo a um rio, 222 m. s.m., 23°14'99"S, 44°47'68"W, fl., fr., 18 Dec 2007, M.G. Bovini et al. 2694 (holotype: RB barcode RB00537845!; isotypes to be distributed to: R!, SPF!, US!).

Description.

Herbs ca. 30-60 cm tall, with an indefinite base, terrestrial. Stems prostrate with ascending apex, delicate to slightly succulent, branched to densely branched; internodes 1.8-4.5 cm long at base, distally shorter, medium to dark green, glabrous, with a leaf-opposed dense longitudinal line of short, uniseriate, brown to light brown hairs. Leaves distichously-alternate, sessile; ptyxis involute; sheaths 4.1-7.6 mm long, medium green, glabrous, with a dense setose line of uniseriate hairs opposed to the blade, margin densely setose, hairs light to medium brown; blades 6.4-13.6 × 1.9-3.8 cm, lanceolate to elliptic to linear oblong, flat, membranous, adaxially sparsely hispid to hispid, abaxially hispid, adaxially dark to medium green, abaxially light to medium green, turning olive-green or medium brown when dry, base rounded to cordate, margins green, ciliate, setose at base, flat, apex acuminate; midvein conspicuous, adaxially impressed, secondary veins conspicuous, adaxially impressed, abaxially inconspicuous, becoming more evident on both sides when dry. Synflorescences terminal or axillar in the distal portion of the stems, composed of a solitary main florescence, 1 per leaf axis. Inflorescences (main florescences) consisting of a pedunculate double-cincinni fused back to back; peduncles 1.9-3.8 cm long, medium to dark green, glabrous, with a dense longitudinal line of short, uniseriate, light to medium brown hairs; cincinni bracts 3.8-7.7 × 1-2.6 cm, unequal to strongly unequal to each other, lanceolate to ovate, leaf-like, adaxially sparsely hispid to hispid, abaxially hispid, adaxially dark to medium green, abaxially light to medium green, base cordate to obtuse, saccate, margin ciliate, setose at base, flat, apex acuminate; double-cincinni 6-12-flowered. Flowers 1.2-1.5 cm diam., pedicels 0.5-1.3 cm long, medium to dark green, distally sparsely glandular-pubescent, hairs hyaline; floral buds ovoid; sepals 4.6-6.5 × 3-4.8 mm, dorsally keeled, medium green, setose along the keel, hairs hyaline; petals 5.9-7.5 × 3-4.3 mm, flat, white; filaments 4.9-5.8 mm long, anthers 0.4-0.6 × 0.6-0.9 mm; ovary 1.3-1.7 × 1.1-1.3 cm, style 4-5.1 mm long; pistil the same length as the stamens. Capsules 4.2-5 × 3.4-4.3 cm. Seeds 1.5-1.8 × 1.2-1.4 mm, testa light to medium grey, not cleft towards the embryotega, costate; hilum longer than ½ the length of the seed.

Distribution and habitat.

Tradescantia hertweckii is endemic to Brazil, more precisely to the state of Rio de Janeiro, municipality of Paraty; in the Atlantic Forest domains (Fig. 23 ). It can be found growing as a terrestrial, understorey in shaded and moist forests, near river margins.

Phenology.

It was found in bloom and fruit in December, during the rainy season.

Etymology.

This species is named after Dr. Kate Hertweck, dear colleague and specialist in subtribe Tradescantiinae , in appreciation for her contributions to the systematics and evolution of Monocots and Commelinaceae , especially regarding the evolution of Tradescantia .

Conservation status.

Tradescantia hertweckii is known solely from the type collection and, following the IUCN recommendations ( IUCN 2001), it should be considered Data Deficient (DD), until further collections and information becomes available.

Comments.

Tradescantia hertweckii was considered by me a doubtful specimen related to T. fluminensis and, for this reason, not included in my Master thesis in the initial account for T. subg. Austrotradescantia (at the time T. sect. Austrotradescantia ; Pellegrini 2015). It was thought by me to putatively represent a natural hybrid between T. fluminensis and T. umbraculifera , but it differed greatly from the other putative hybrids. Added to that, the inflorescence morphology of T. hertweckii is very similar to the one of T. fluminensis and does not show the very peculiar inflorescence of T. umbraculifera (Fig. 5I ). Finally, T. umbraculifera is not known to occur in the same locality as T. hertweckii , with the only other species in the subgenus known to occur in Paraty being T. fluminensis . For these reasons, I have decided to recognise T. hertweckii as a new species, instead of a natural hybrid.

Tradescantia hertweckii is the only species from T. subg. Austrotradescantia not included by Pellegrini (2017) in his morphological phylogeny for the genus. However, it is a member of the T. fluminensis group, due to its indefinite base, stems prostrate with ascending apex, involute ptyxis, leaf-blades with conspicuous secondary veins (Fig. 22A ), saccate cincinni bracts (Fig. 22A ), pistil the same length as the stamens Fig. 22G ) and seeds with costate testa not cleft towards the embryotega (Figs 7C , 22O ). It is morphologically similar to T. fluminensis and T. umbraculifera . Tradescantia hertweckii is morphologically similar to T. umbraculifera due to its robust habit, sessile leaves, acuminate to caudate leaf-blades (Fig. 22A ) and hilum longer than ½ the length of the seed (Figs 7C , 22O ). Nonetheless, it can be easily differentiated from T. umbraculifera by its membranous to slightly fleshy leaf-blades covered by hispid indumentum (vs. chartaceous and glabrous or pilose in T. umbraculifera ), 1 inflorescence per leaf axil (vs. 1-4), cincinni bracts leaf-like and unequal to strongly unequal (vs. spathaceous and equal), pedicels green at pre-anthesis and anthesis (vs. white) and pistil as long as the stamens (vs. longer than the stamens). On the other hand, T. hertweckii might be more easily confused with T. fluminensis s.s., due to its glabrous stems (Fig. 22A ), membranous to slightly fleshy leaf-blades, 1 inflorescence per leaf axil, leaf-like cincinni bracts (Fig. 22A ), sepals with eglandular hairs restricted to the keels (Fig. 22H, N ) and pistil as long as the stamens (Fig. 22 G ). However, both species can be differentiated based on leaf morphology (leaves sessile, blades hispid, margins ciliate with densely setose base in T. hertweckii vs. subpetiolate, glabrous, evenly ciliolate in T. fluminensis ), inflorescence morphology (cincinni bracts unequal to strongly unequal vs. equal), sepal pubescence (setose vs. pilose), petal posture (flat vs. plicate) and hilum relative length (longer than ½ the length of the seed vs. equal).

Figures

Figure 5. Inflorescence architecture in Tradescantia subg. Austrotradescantia A malformed main florescence of T. cymbispatha, showing the subopposite cincinni B detail of the synflorescence of T. crassula, showing an axillary inflorescence composed of solitary cincinnus and a terminal with the typical double-cincinni with non-saccate cincinni bracts C-D inflorescence in T. decora (removed) C inflorescence composed of 4 - cincinni, showing the spathaceous and supernumerary bracts (removed) D synflorescence, showing main florescences and coflorescences ranging from regular double-cincinni to 3 - 5 - cincinni (removed) E front view of the main florescence of T. fluminensis, showing the saccate cincinni bracts F dorsal view of the main florescence of T. mundula, showing the saccate cincinni bracts G main florescence of T. seubertiana, showing the unequal and non-saccate cincinni bracts H main florescence of T. tenella, showing the strongly unequal cincinni bracts I inflorescence of T. umbraculifera, showing the main florescence and a coflorescence emerging from the same leaf axil. Photos by M. O. O. Pellegrini. See the Erratum note.

Figure 7. Fruit and seed morphology in Tradescantia subg. Austrotradescantia. A mature and dehisced capsule of T. cerinthoides B dorsal and ventral views of the seed of T. crassula, showing the costate testa cleft towards the embryotega and the hilum longer than 1 / 2 the length of the seed C dorsal and ventral views of the seed of T. hertweckii, showing the costate testa not cleft towards the embryotega and the hilum equal to 1 / 2 the length of the seed D dorsal and ventral views of the seed of T. atlantica, showing the rugose testa not cleft towards the embryotega and hilum shorter than 1 / 2 the length of the seed. Photos by M. O. O. Pellegrini.

Figure 22. Tradescantia hertweckii M. Pell. A habit B detail of the leaf-sheaths, showing the setose margins C hair from the margin of the leaf-sheath D-E leaves D detail of the abaxial side of the apex of the blade, showing the hispid indumentum E detail of the adaxial side of the apex of the blade, showing the hispid indumentum F-G flowers F front view of a flower G oblique view of a flower H sepals, showing the setose indumentum restricted to the dorsal keels I petal J-K androecium J stamen K detail of the anther L-M gynoecium L pistil M detail of the stigma N open mature capsule O seeds, showing the costate testa not cleft towards the embryotega and the hilum longer than 1 / 2 the length of the seed. Line drawings by M. A. Rezende.

Figure 23. Distribution of Tradescantia hertweckii M. Pell. Orange- Cerrado; Olive-green- Pampa; Dark green- Atlantic Forest.