Tradescantia hertweckii M.Pell.

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

publication ID

http://dx.doi.org/10.3897/phytokeys.104.28484

persistent identifier

http://treatment.plazi.org/id/2743932F-B465-6783-8024-7FF6D26CE658

treatment provided by

PhytoKeys by Pensoft

scientific name

Tradescantia hertweckii M.Pell.
status

sp. nov.

8. Tradescantia hertweckii M.Pell.  LSID  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 Coriscão, 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).

Kingdom

Plantae

Phylum

Tracheophyta

Class

Liliopsida

Order

ORDO

Family

FAMILIA

Genus

Tradescantia