Merianthera calyptrata R.Goldenb., Bochorny & Fraga, 2023

Goldenberg, Renato, Bochorny, Thuane, Amorim, André Márcio, Ziemmer, Juliana Klostermann & Fraga, Claudio Nicoletti de, 2023, Merianthera calyptrata sp. nov. (Melastomataceae, Myrtales), a new candelabriform species from Minas Gerais, Brazil, European Journal of Taxonomy 888, pp. 64-76 : 67-71

Merianthera calyptrata R.Goldenb., Bochorny & Fraga sp. nov.

urn:lsid:ipni.org:names:77324801-1

Figs 1–4

Diagnosis

Merianthera calyptrata sp. nov. differs from Merianthera burlemarxii by the acute or slightly cuneate leaf base (vs obtuse to rounded in M. burlemarxii ), rounded to seldom obtuse apex (vs acuminate or abruptly acuminate), the solitary flower on a single, ebracteolate pedicel, borne directly on the stem, i.e., not borne on a peduncle (vs solitary, bibracteolate, pedicellate flower borne on a short peduncle), calyx closed in bud, calyptrate, dehiscing through a transversal, circumscissile slit that releases a single, conical cap (vs open in bud, with five regular sepals), fruits opening regularly through (3–)4 longitudinal slits running from the apex to almost the base of the fruit (vs fruits opening irregularly, with no apparent line of dehiscence, and the seeds are dispersed as the hypanthium and ovary walls decay and open; fide Goldenberg et al. 2012).

Etymology

The epithet refers to the flowers with a calyptrate calyx, a unique feature of M. calyptrata sp. nov., and otherwise unknown in the genus and tribe.

Material examined

Type BRAZIL – Minas Gerais • Jacinto, Comunidade de Medeiros , “ acesso a esquerda na MG-405 sentido Jacinto - Jaguarão , propriedade do Sr. Augusto Chavier de Souza ”; 16°15′25″ S, 40°4′27″ W; 30 Mar. 2022; Claudio N. de Fraga & Dayvid R. Couto 4144; holotype: RB [ RB01463285 ]; isotypes: BHCB, K, MBML, NY, UPCB .

Paratype BRAZIL – Minas Gerais • Jacinto , “ Inselbergs no lado esquerdo da MG 405, em direção sul ”; 16°10′10″ S, 40°17′13″ W; 1 Feb. 2022; A.M. Amorim, F. Cabral & Y. Gouvea 11854; RB, UESC, UPCB .

Description

Shrubs or treelets up to 2.5 m tall. Branches candelabriform, light brown at the very tip, becoming reddish-brown to dark-vinose (blackish in dried specimens) below the leaf line, terete, each segment is basally thin (0.4–0.6 mm diam.), becoming very thick at its apex (8–11 mm diam.), apparently solid (but becoming hollowed in dried material, with fistulae 2–5 mm high), the surface with the distinct leaf scars sometimes topped by flower scars and always flanked by two white lenticels (one at each side), when young moderately to densely granulose-glandulose and glutinous, the minute, sessile, yellowish glands (in dried specimens), partially covered with a layer of a viscous, shiny, yellowish substance. Leaves isomorphic, with petioles 0.6–1 cm long; blade 4–7 × 1.5–3.5 cm, elliptic to spatulate, base acute to slightly cuneate, apex rounded or seldom obtuse, chartaceous, discolorous both in fresh and dried specimens, acrodromous nerves 3, distinctly suprabasal (distant 0.5–1.2 mm from the base), the laterals sometimes joining the main nerve at the apex, but sometimes joining the leaf margins very near the leaf apex before joining the main nerve and leaf apex, with an additional faint submarginal pair originating near the leaf base and fading away about ½ to ⅔ of the blade length, main nerve, laterals, transversals and reticulation plane or impressed on adaxial surface and prominent (main nerves) to plane (transversal and reticulation) on abaxial surface, adaxial surface sparse to moderately granulose-glandulose and glutinous (the sessile glands denser on the nerves and nearby surfaces), abaxial with dense vermiform, usually eglandular trichomes 50–230 µm long (measurements from SEM images), mixed with the same minute, sessile, yellowish glands 20–35 µm long (measurements from SEM images) found in young stems and the adaxial leaf surface, the vermiform trichomes restricted to the areolae and absent on the nerves and reticulation and the sessile glands present on both, the glutinous cover thin, i.e., not immersing the vermiform trichomes. Flowers solitary, axillary or sometimes cauliflorous (then from an axillary bud right above a scar left by a caducous leaf), peduncles absent, ebracteate, ebracteolate; 5-merous, on pedicels 10– 19 mm long (the pedicel apex hard to distinguish from the tapering hypanthium base). Hypanthium 7–10 × 5–7 mm, greenish brown in mature flowers, conical, outside slightly costate-sulcate, strongly glutinous, apparently moderately to densely glandulose-granulose below the glutinous layer, otherwise glabrous, inside almost totally adhered to the ovary, except for a short, up to 1 mm long, glabrous projection, torus glabrous. Calyx closed and yellowish-green in bud (contrasting with the darker hypanthium), dehiscent through a transversal, circumscissile, clean slit that releases a single conical, yellowish-brown calyptra 11–15 × 6–8 mm, solid (i.e., the tip not hollowed as in Michelangeli & Goldenberg 2021), no evident sepals nor external tooth, no tube remaining on the hypanthium, outside with the same indumentum as the hypanthium, inside sparsely to moderately covered with minute, vermiform, both glandular and eglandular trichomes, but the omnipresent sessile glands very sparse. Petals 21–24 × 14–15 mm, purple in recently opened flowers, lighter and pink in older flowers, adaxial surface shortly papillose, otherwise glabrous on both surfaces, deflexed at anthesis, membranaceous, broadly elliptic, apex rounded or obtuse, margins undulate, not revolute. Stamens 10, dimorphic; antesepalous with filaments 16–18 mm long, purple to pinkish (in older flowers), connective purple to reddish, with light yellow to cream extremities, prolonged ca 0.5 mm below the thecae, the ascending appendage 3.5–3.7 mm long, bilobed at the apex, the descending appendage 2–2.3 mm long, narrowly triangular, acute apex, anthers whitish, 4–4.2 mm long, straight; antepetalous with filaments 10–11 mm long, purple to pinkish (in older flowers), connective light yellow to cream, 0.6–0.7 mm prolonged below the thecae, the ascending appendage 4.9–5.2 mm long, straight, bilobed at the apex, the descending appendage ca. 1 mm long, blunt, anthers dark purple, 5–5.7 mm long, straight. Ovary 7–10 mm long, (3–)4-celled, stylar column almost absent, less than 1 mm long, glabrous; style 11–13 mm long, glandular-puberulous on its basal ⅔, straight with a strongly curved apex, stigma punctiform. Fruits 12–20 × 8–15 mm (including pedicels), not constricted at the apex, opening regularly through (3–)4 longitudinal, loculicidal slits running from the apex to near the base of the fruit, these (3–)4 segments encompassing both the ovary wall and hypanthium; placentae persistent. Seeds not seen.

Distribution, habitat and phenology

Merianthera calyptrata sp. nov. has been recorded three times (two collections and one photo), all from the same locality. The municipality of Jacinto lies on the Minas Gerais side of the border with Bahia, to the south (right margin) of the Jequitinhonha River ( Fig. 5 ). These plants grow on granitic inselbergs ( Fig. 4 ), right on the exposed surface, among other herbaceous, climbing, and shrubby species from genera that are very common on inselbergs ( Alcantarea (É.Morren ex Mez) Harms , Mandevilla Lindl. , Piptadenia Benth. , Pseudobombax Dugand , Pleroma D.Don , and Stillingia Garden ) in small vegetation clusters. The climate in this region is highly seasonal, with a strong dry season in winter and a wet summer. The plants were collected with very young flower buds (Amorim et al. 11854) and photographed with flowers (by Mr Reginaldo Vasconcelos) in February, then it was collected with open flowers in March (Fraga & Couto 4144), from the middle to the end of the rainy season; both collections had old, persistent, seedless fruits from the previous season, which indicates that the fruits may be present all year long.

Preliminary conservation assessment

This species has been found in only two close locations at a single locality, both outside protected areas and within private properties where cattle is raised. Vegetation on inselbergs is naturally fragmented, and this fragmentation may be intensified by grazing. On the other hand, rock outcrops usually do not attract much agricultural interest, and consequently, they have frequently been preserved from human impact and have kept their refugial character ( Porembski et al. 1998).

According to Guidelines for Using the IUCN Red List Categories and Criteria ( IUCN 2022), it should be considered Data Deficient (DD) due to poor sampling. However, AOO of Merianthera calyptrata sp. nov. is currently 8 km 2, and its EOO cannot be defined. Although these figures are within limits for Critically Endangered (CR), under the criterion B2 (AOO less than 10 km 2), the number of locations is greater than 1 and falls within the Endangered (EN) category.

We don’t have reliable information about continuing decline or extreme fluctuations of populations of this species, but two of the authors of this article made an intensive evaluation of this species in loco, since they were in this place looking precisely for these plants. Due to its apparent rarity and restricted endemic distribution and the fact that their populations are prone to the effects of stochastic events in the near future, it seems prudent to include this species in the Vulnerable category [VU: D2].

Figures

Fig. 1. Illustration of Merianthera calyptrata R.Goldenb., Bochorny & Fraga sp. nov. A. Fertile branch. B. Detail of the branch showing leaf and flower scars plus two lenticels, each at one side of the leaf scar. C. Branch tip with leaves, flower buds, an open flower and a fruit. D. Flower opening sequence, from left to right: flower bud, with the calyptrate calyx still attached to the hypanthium; flower bud, with a circumscissile dehiscence, but the calyptra still holding the petals together; and young flower, with the calyptrate calyx falling from the petal tips. E. Petal, adaxial surface. F. Flower in longitudinal section (calyx, petals and stamens removed) with detail of trichomes at the base of style. G. Antesepalous stamens, from bud (left) and mature flower (right). H. Antepetalous stamens, from bud (right) and mature flower (left). I. Antepetalous stamen, detail of the pore. From Fraga & Couto 4144 (all drawings). Drawn by Diana Carneiro.

Fig. 2. Field photographs of Merianthera calyptrata R.Goldenb., Bochorny & Fraga sp. nov. A. Fertile branch. B. Branch apex, longitudinal section showing the fistulose structure of the stem, with the chambers filled with parenchyma. C–E. Sequence of flower anthesis, showing the calyptrate calyx with its circumscissile dehiscence.F. Flowers, frontal view. G. Stamens and style, lateral view. H. Old flower, lateral view; this photo shows the single, ebracteolate flower and the absence of a peduncle. I. Mature fruit. From: Fraga & Couto 4144 (A–H), Amorim et al. 11854 (I). Photos by C.N. Fraga (A–H) and Y. Gouvea (I).

Fig. 3. Merianthera calyptrata R.Goldenb., Bochorny & Fraga sp. nov., scanning electron micrographs of the abaxial surface of the leaf. A. General view.B. Detail of the dense vermiform trichomes (arrow) mixed with sessile glands (arrowhead). Scale bars: A = 200 µm; B = 100 µm. From A.M Amorim et al. 11854 (UPCB).

Fig. 4. Merianthera calyptrata R.Goldenb., Bochorny & Fraga sp. nov. in its habitat. A. Inselberg and granitic outcrops where the plant can be found. B. Vegetation cluster growing on a cleft, on a granitic outcrop, with M. calyptrata to the right and front, with flowers. C. Three individuals with spreading crowns, behind some Alcantarea (É.Morren ex Mez) Harms (Bromeliaceae). From Fraga & Couto 4144. Photos by C.N. Fraga.

Fig. 5. Distribution of Merianthera calyptrata R.Goldenb., Bochorny & Fraga sp. nov. and its closest relative, Merianthera burlemarxii Wurdack. BA = Bahia; ES = Espírito Santo; MG = Minas Gerais.