Microlicia pithyoides (Cham.) Versiane & R.Romero, Bot. J. Linn. Soc. 197: 54. 2021.

Pacifico, Ricardo, Almeda, Frank, Penneys, Darin S. & Fidanza, Karina, 2022, Systematics of the Trembleya sensu stricto clade of Microlicia (Melastomataceae, Lavoisiereae), PhytoKeys 216, pp. 1-101 : 1

8. Microlicia pithyoides (Cham.) Versiane & R.Romero, Bot. J. Linn. Soc. 197: 54. 2021.

Fig. 27

Trembleya pithyoides Cham., Linnaea 9(4): 428. 1835. basionym. Type: Brazil. “Caraça” [Minas Gerais, Serra do Caraça], 20 December 1830, F. Sellow 1316 (lectotype, designated here: K [K00530665]!; isolectotypes: F-BN016638-photo]!, P [P00723396]!, P [P00723397]!; image of isolectotype at P is available at http://coldb.mnhn.fr/catalognumber/mnhn/p/p00723396).

Trembleya pithyoides var. major Cogn. in Martius et al., Fl. Bras. 14(4): 594. 1888. syn. nov. Type: Brazil. "Minas, Serra de Capanema" [Minas Gerais, Santa Bárbara], 21 February 1884, A.F.M. Glaziou 14746 (lectotype, designated here: P [P00723395]!; isolectotypes: BR [BR0000005223930]!, BR [BR0000005520169]!, C [C10015114-online image]!, C [C10015113-online image]!, K [K00530666]!, P [P00723394]!, P [P00723393]!; image of lectotype is available at http://coldb.mnhn.fr/catalognumber/mnhn/p/p00723395).

Description.

Erect, densely-branched shrubs 0.3-0.6 m tall. Branchlets quadrangular, glandular-punctate, vinaceous (when fresh). Internodes 0.2-0.5 cm long, angles with narrow wings ca. 0.2 mm wide. Petioles 0.7-1.5 mm long. Leaf blades 4-15 mm long, 0.5-1.4 mm wide, chartaceous (when dry), linear, both surfaces green (when fresh), adaxial surface blackened and abaxial surface pale green to pale brown (when dry), discoloured (when dry), base cuneate, apex rounded to acute, margin flat, entire and glandular-punctate, 1-nerved from the base, tertiaries not evident on the abaxial surface, adaxial surface glandular-punctate, abaxial surface glandular-punctate. Inflorescences reduced to solitary flowers apically on the branches. Bracts absent. Bracteoles (at anthesis) with petioles 0.6-0.9 mm long, blades 3.0-3.9 mm long, 0.3-0.5 mm wide, lanceolate, base cuneate, apex acute to obtuse, margin entire, 1-nerved, indumentum like that of the principal leaves. Flowers 5-merous, pedicels (at anthesis) 0.3-0.6 mm long. Hypanthia (at anthesis) 1.7-2.0 mm long, 1.9-2.1 mm wide at the torus, campanulate, light green or reddish (when fresh), externally glandular-punctate. Calyx tubes 0.3-0.4 mm long. Calyx lobes (at anthesis) 2.5-3.0 mm long, 0.4-0.7 mm wide at the base, subulate, apex acute, margin entire, (when fresh) light green or reddish externally like the hypanthia. Petals 5.0-5.7 mm long, 3.7-4.2 mm wide, magenta, obovate, apex acuminate, margin entire and glabrous, adaxial surface glabrous or sparsely glandular-punctate, abaxial surface glabrous. Stamens 10, strongly dimorphic. Larger (antesepalous) stamens 5, filaments 2.6-2.9 mm long, pink, pedoconnectives 2.9-3.2 mm long, pink, appendages 0.7-0.9 mm long, yellow, apex emarginate to bilobate, thecae (excluding rostra) 1.8-2.0 mm long, vinaceous, oblong, rostra 0.2-0.4 mm long, the circular pores ca. 0.2 mm wide. Smaller (antepetalous) stamens 5, filaments 1.9-2.1 mm long, pink, pedoconnectives 0.6-0.9 mm long, yellow, inconspicuous appendages ca. 0.1 mm long, yellow, apex emarginate, thecae (excluding rostra) 1.4-1.6 mm long, yellow, oblong, rostra 0.2-0.3 mm long, the circular pores ca. 0.2 mm wide. Ovary 1.3-1.5 mm long, 1.0-1.2 mm wide, globose, (4-)5-locular. Style 4.0-4.5 mm long, pink. Capsules (at maturity) 2.7-3.1 mm long, 2.9-3.3 mm wide, globose, initially enveloped by the hypanthium, torus constricted at the apex, fruiting calyx tubes 0.4-0.6 mm long, fruiting calyx lobes 3.2-3.7 mm long, not thickened. Seeds 0.7-0.8 mm long, reniform.

Specimens examined.

Brazil. Minas Gerais: Catas Altas Municipality, Serra do Caraça, Oliveira 382 (BHCB, RB), Pacifico 295 (CAS, HUEM, SPF); Unknown municipality in Minas Gerais State , Serra do Caraca . Glaziou 14746 (BR, C, K, P, R), Glaziou 19239 (K, P), Sellow 1316 (lectotype: K [K00530665; isolectotypes: F-BN016638-photo, P [P00723396], P [P00723397]), Sellow s.n. (K [K00957781, K [K00957783]), Weddell s.n. (P [P005317975]) .

Distribution, habitat and elevation range.

Known only from Minas Gerais State (Fig. 25B ), where it is probably endemic to the Serra do Caraça. Microlicia pithyoides grows on quartzitic campo rupestre exposed to full sun at elevations between 1827 and 2072 m. It is the only species in the clade that reaches the highest peak in Cadeia do Espinhaço, the Pico do Sol in Catas Altas Municipality (elev. 2,072 m) (personal observation by R. Pacifico).

Conservation.

Microlicia pithyoides species is the least collected species of the Trembleya s.s. clade and apparently has the narrowest distribution. Less than 10 collections of this species are housed in herbaria. It had not been collected for more than a hundred years until it was re-discovered in 2009 (Oliveira 382). As all coordinates available for M. pithyoides refer to the same population, we were unable to calculate its EOO. The AOO is 4 km2. The only population known of this species occurs inside a private protected area, the RPPN Serra do Caraça (Natural Heritage Private Reserve). The type material was probably collected at the Serra de Capanema in Santa Bárbara Municipality. Currently, this locality is also part of a private property. We are not aware of recent collections of M. pithyoides from the Serra de Capanema. Overall, the vegetation of Serra do Caraça is largely intact and affords a good measure of protection for the populations of M. pithyoides . This species is considered Critically Endangered by the Brazilian Government ( Brasília 2014). Based on criterion B of the IUCN (2019), we concur with this assessment: (CR): B1ab(iii).

Recognition and affinities.

Microlicia pithyoides can be recognised by its narrow leaves that are 0.5-1.4 mm wide, 1-nerved from the base, inflorescences reduced to solitary flowers, magenta petals and stamens with bicoloured anthers. In morphology, it is most like M. rosmarinoides , the only congener with leaves that are 1-nerved from the base. Microlicia rosmarinoides also shares with M. pithyoides the solitary flowers with subulate calyx lobes and the overall shape of its stamens. Microlicia pithyoides differs from M. rosmarinoides by the leaves with the mid-vein thickened (vs. not thickened), magenta petals (vs. yellow) and stamens with anthers vinaceous and yellow (vs. all anthers yellow to orange). Both species occur in central Minas Gerais State, but their distributions do not overlap; M. rosmarinoides has never been collected on the Serra do Caraça.

Microlicia calycina is also morphologically similar. It shares with M. pithyoides the narrow leaves, solitary flowers (sometimes simple dichasia only in M. calycina ), magenta petals and stamens with bicoloured anthers. Microlicia pithyoides may be differentiated by its leaf blades (oblong to lanceolate) 0.5-1.4 mm wide (vs. 2-9 mm wide), 1-nerved from the base (vs. 3-nerved) with tertiaries not evident (vs. evident) and shorter calyx lobes 2.5-3.0 mm long (vs. 3.5-4.2 mm long). Both M. calycina and M. pithyoides occur sympatrically on the Serra do Caraça, but only M. pithyoides occurs on the highest peak in that mountain range. In fact, M. pithyoides apparently prefers slightly higher elevations since it has only been collected between 1827 and 2072 m (vs. 1692-1920 m for M. calycina ).

Notes.

Recent collections of M. pithyoides (Oliveira 382, Pacifico 295) have leaves with blades that are 8-12 mm long. These measurements bridge those given in the protologues of varieties Trembleya pithyoides (8-10 mm long) and Trembleya major (12-20 mm long). We consider these size differences to represent a continuum and here relegate Trembleya pithyoides var. major to synonymy.

Figures

Figure 25. Geographic distribution of species of the Trembleya s. s. clade of Microlicia A distributions of M. parviflora and M. tridentata B distributions of M. pentagona, M. pithyoides and M. rosmarinoides.

Figure 27. Microlicia pithyoides A habit B detail of nodes and internodes C leaf abaxial surface D bracteole abaxial surface E floral bud F flower in lateral view G petal adaxial surface H antesepalous stamen I antepetalous stamen J capsule enveloped by the hypanthium K capsule in cross section. Drawn from Pacifico 295 (CAS).