Marcetia unguiculata R. B. Pacifico & Almeda 2022, sp. nov.
Creators: name: Pacifico, Ricardo
name: Almeda, Frank
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Myrtales
Melastomataceae
Marcetia
Marcetia unguiculata

description: Marcetia unguiculata R.B.Pacifico & Almeda, sp. nov. (Figs. 8–9).
Type:— BRAZIL. Bahia: Mucugê. Distrito de Guiné, na trilha que sobe para a Serra do Esbarrancado, 12°45’22”S, 41°30’42”W, 1167 m, 1 December 2019, fl., R.M. Harley 58555, A.M. Giulietti, L.T. Carneiro, S.A. Lima & O. Domingo (holotype: HUEFS!).
Diagnosis:— Differs from Marcetia alba Ule (1908: 236) by the elliptic leaf blades (vs. deltoid to cordiform) that are eciliate (vs. ciliate with glandular trichomes), calyx lobes triangular (vs. linear), petals with conspicuous claws 1–1.3 mm long (vs. base attenuate, claws absent), stamens with shorter filaments 0.8–1.2 mm long (vs. 2.8–3.2 mm long), and anthers 1–1.5 mm long (vs. 2–3 mm long).
Erect rupicolous shrub up to 0.5 tall, dichotomously branched. Upper cauline internodes 2–7 mm long, light green (when fresh) becoming pale green (when dry), quadrangular, not sulcate, glabrous or with sparse inconspicuous hyaline trichomes up to 0.2 mm long. Leaves decussate, spreading, not concealing the uppermost internodes, papyraceous, discolored (when fresh), adaxial surface shiny green, abaxial surface pale green, both leaf surfaces becoming pale brown (when dry); petioles 0.7–1 mm long; blades 3.5–6.5 × 2–3 mm, flat, elliptic, apex rounded to acute, base rounded to attenuate, margins entire, eciliate, adaxial surface glabrous, abaxial surface densely covered with inconspicuous hyaline trichomes ca. 0.2 mm long, 5–7-nerved from the base (basal acrodromous), venation prominent on the abaxial surface and impressed on the adaxial surface, secondary venation not evident. Flowers 4-merous on pedicels 2–4 mm long (lengthening to 6 mm long in fruit), concentrated at the apex of the branches, ebracteolate. Hypanthia (at anthesis) 2–2.5 mm long, 1.8–2 mm wide at the torus, reddish, campanulate, equaling the capsule in length at maturity, glabrous. Calyx tube inconspicuous, ca. 0.1 mm long. Calyx lobes 1.8–2.1 mm long, 1.7–2 mm wide at the base, reddish (when fresh) becoming brownish (when dry), patent at anthesis, triangular, apex rounded to acute, margins entire and glabrous, both surfaces glabrous. Petals 4–5 × 4–5 mm (including claw that is up to 1–1.3 mm long), the blade orbicular to slightly reniform, magenta, apex obtuse, both surfaces glabrous, margins entire and beset with minute hyaline trichomes ca. 0.1 mm long. Stamens 8, isomorphic, erect and clustered around the base of the style; filaments 0.8–1.2 mm long, white becoming red with age or following pollination, glabrous; anthers 1–1.5 × 0.3–0.5 mm, yellow, oblong, erostrate, pedoconnectives up to 0.3 mm, unappendaged. Ovary (at anthesis) ca. 1 × 0.8 mm, superior, globose, glabrous, 4-locular, not adnate to the hypanthium; style ca. 2–3 mm long, magenta, glabrous, incurved, stigma punctiform. Fruit at maturity a globose loculicidal capsule 2–3 × 2–3 mm, pale brown, glabrous, 4-valvate, enveloping hypanthia and rupturing and flaking away with age. Seeds ca. 0.8 × 0.3 mm, brown, rounded-cochleate, testa tuberculate, raphal zone elliptic, ca. 40% the length of the seed.
Additional specimens examined:— BRAZIL. Bahia: Mucugê, Beco do Guiné no acesso ao Vale do Pati, Parque Nacional da Chapada Diamantina, Subida da Serra do Esbarrancado, ca. 1300 m, 25 June 2022, fl., fr., R. Pacifico et al. 707 (CAS!, HUEM!, RB!); Serra do Esbarrancado, no Topo da Serra, 1300 m, 1 November 2011, fr., fr., R.P. Oliveira et al. 1964 (HUEFS!).
Distribution, habitat and phenology:— Probably endemic to the campo rupestre of Guiné, Mucugê, Bahia, Brazil (Figs. 3, 4E; Appendix 2). It grows on partially shaded rocky walls at elevations of ca. 1300 m. Collected flowering and fruiting in November, December and June.
Etymology:— The epithet refers to the unguiculate petals of this species that are markedly narrowed into a petiolelike base.
Notes:— Marcetia bahiana (Ule 1908: 236) A.B. Martins (1995a: 149) is another species that is morphologically similar to M. unguiculata. Both M. bahiana and M. unguiculata are rupicolous shrubs that grow in shaded sites. They share elongated leaves with the margins ciliate, ebracteolate flowers with pink/magenta petals, isomorphic stamens, and 4-locular ovaries. Marcetia unguiculata differs by the elliptic leaf blades (vs. lanceolate to oblong-lanceolate in M. bahiana) that are 5–7-nerved from the base (vs. 1-nerved), the calyx lacking intercalycine rigid eglandular trichomes (vs. present), calyx lobes triangular 1.8–2.1 mm long (vs. lanceolate, 2.5–3 mm long), unguiculate petals (vs. petals with an attenuate base, claws absent), and shorter stamen filaments 0.8–1.2 mm long (vs. 2.8–3 mm long).
Marcetia bahiana was long considered as a possibly extinct species (CNCFlora 2022). It was recently rediscovered in Serra do Gobira (R. Pacifico et al. 711, CAS), 116 years after the type specimen was collected by Ernst Heinrich Georg Ule at the Serra do Sincorá (see Ule 1908). In this context, it appears that both M. bahiana and Marcetia unguiculata are endemic to Mucugê. Still, they are known from different localities, i.e., the Serra do Gobira (Fig. 4F) and the Serra do Esbarrancado (Fig. 4E), respectively. The more widely distributed Marcetia alba has also been reported for Mucugê, making sympatric occurrence with M. unguiculata possible (see Appendix 1).
Suggested conservation status:— Data Deficient (DD) (see Appendix 2).
description: Published as part of Pacifico, Ricardo & Almeda, Frank, 2022, New species of Marcetia and Microlicia (Melastomataceae) endemic to the campo rupestre of Chapada Diamantina, Bahia, Brazil, pp. 39-69 in Phytotaxa 573 (1) on pages 47-49, DOI: 10.11646/phytotaxa.573.1.3, http://zenodo.org/record/7329459