Microlicia tetramera Almeda & R.B.Pacifico, 2022

Pacifico, Ricardo & Almeda, Frank, 2022, New species of Marcetia and Microlicia (Melastomataceae) endemic to the campo rupestre of Chapada Diamantina, Bahia, Brazil, Phytotaxa 573 (1), pp. 39-69 : 62-63

Microlicia tetramera Almeda & R.B.Pacifico , sp. nov. ( Figs. 22–23 ).

Type:— BRAZIL. Bahia : Rio de Contas , Arapiranga, Gerais do Porco Gordo, Rio Galinha, 13°25’59.1”S, 41°45’09.2”W, 1174 m, 17 June 2022, fl., fr., R. Pacifico 642, V.E. Bressan & E.A. Ramos (holotype: HUEM!, isotypes: ALCB!, CAS!, HUEFS!, RB!, SPF!) .

Diagnosis:— Differs from all congeners by its consistently 4-merous flowers (vs. 5–8-, rarely 9–10-merous in the remaining species). It differs from Microlicia juniperina Saint-Hilaire (1833: 373) by the 4-merous flowers (vs. 5- merous), petals yellow (vs. magenta), isomorphic stamens (vs. dimorphic) that are entirely yellow (vs. yellow and magenta), and 2-locular ovaries (vs. 3-locular).

Erect shrubs 0.6–0.7 m tall, much-branched. Upper cauline internodes 2.5–3.5 mm long, light green (when fresh) becoming pale green (when dry) and defoliated with age, quadrangular, not sulcate, unwinged, glabrous. Leaves decussate, ascending, concealing uppermost internodes (both when fresh and when dry), papyraceous, concolored, vivid green with a reddish apex (when fresh) becoming pale green (when dry), sessile; blades 4–6 × 0.3–0.5 mm, subulate, apex acuminate, terminating in a reddish needle-like trichome 0.2–0.4 mm long, base truncate, margins entire and eciliate, concave-conduplicate, both surfaces glabrous, lacking evident venation. Flowers 4-merous on inconspicuous pedicels 0.1–0.2 mm long, apical, solitary, ebracteolate. Hypanthia (at anthesis) 2.1–2.5 mm long, 1.3– 1.7 mm wide at the torus, light green (when fresh) becoming pale brown in fruit (and when dry), obconical, equaling the capsule in length at maturity, glabrous. Calyx tubes ca. 0.2–0.3 mm long. Calyx lobes (excluding apical trichome) 1.8–2.2 mm long, 1.3–1.5 mm wide at the base, light green (when fresh) becoming pale brown (when dry), patent at anthesis, subulate, apex acuminate, terminating in a reddish needle-like trichome 0.2–0.4 mm long, margins entire and eciliate, externally glabrous. Petals 3.5–4.5 × 2.8–3.2 mm, obovate, yellow, base attenuate, apex acuminate, both surfaces glabrous, margins entire and glabrous. Stamens 8, entirely yellow, isomorphic, erect and clustered around the base of the style (at anthesis); filaments 1.4–1.7 mm long, glabrous, thecae (excluding rostra) 1.2–1.6 × 0.2–0.4 mm, oblong, smooth (tetrasporangiate), rostra 0.1–0.2 mm long, the ventrally inclined pores ca. 0.1 mm wide, nearly circular, pedoconnectives 0.8–1 mm long, the short appendages 0.1–0.2 mm long, apex truncate. Ovary (at anthesis) ca. 1.5 × 0.8–1 mm, superior, subcylindrical, glabrous, 2-locular, not adnate to the hypanthium; style 5–6 mm long, yellow, glabrous, slightly sigmoid, stigma punctiform. Fruit at maturity a globose loculicidal capsule 2–2.5 × 1.4–1.8 mm, pale brown, ovoid, 2-valvate, enveloping hypanthia and rupturing and flaking away with age, dehiscent from the apex to the base (basipetal), columellas deciduous. Seeds ca. 0.3–0.5 × 0.2 mm, yellow, oblong, testa foveolate, raphal zone nearly circular, ca. 25% the length of the seed.

Additional specimens examined: BRAZIL. Bahia : Rio de Contas , Gerais do Porco Gordo , 1170 m, 16 July 1993, fl., fr., W. Ganev 1873 ( HUEFS!, SPF!, UEC-online image!, US!) ; Serra do Porco Gordo / Arapiranga, 13°26’34”S, 41°45’11”W, 1222 m, 17 August 2006, fr., A.K.A. Santos et al. 856 ( HUEFS!) ; Arapiranga, Serra do Porco Gordo , 1226 m, 13 December 2006, fr., A.K.A. Santos et al. 915 ( HUEFS!) .

Distribution, habitat and phenology:— Probably endemic to the Serra do Porco Gordo in Arapiranga, Rio de Contas, Bahia , Brazil ( Fig. 15 , Appendix 2). Microlicia tetramera was collected on rocky outcrops at elevations between 1170–1226 m, exposed to full sun, flowering in June–July and fruiting in June–August and December.

Etymology:— The epithet refers to the uniformly 4-merous flowers that are typical of this species.

Notes:— The 4-merous flowers with 2-locular ovaries of Microlicia tetramera are atypical characters in the Lavoisiereae. Microlicia sphagnicola Gleason (1931: 215) , a Peruvian endemic, was described as having 4-merous flowers. However, specimens collected after its description by Gleason show that this is a variable character in M. sphagnicola (e.g., a 5-merous flower is shown in Figure 3B in Pacifico et al. 2020b). Therefore, Microlicia tetramera is the only known species of the genus (and in Lavoisiereae) with consistently 4-merous flowers. Although atypical, 2-locular ovaries have been described in species of the Lavoisiera clade of Microlicia ( Martins & Almeda 2017) . Microlicia juniperina ( Fig. 5H ), an endemic of the Serra do Cipó in Minas Gerais, resembles M. tetramera in having glabrescent branchlets, sessile subulate leaves that are concave-conduplicate and glabrescent, and subulate calyx lobes (for their distinctions, see the diagnosis). Another relative is Microlicia flavipetala Versiane & R.Romero in Versiane et al. (2021: 53), a Goiás endemic, from which M. tetramera differs by its non-keeled leaves (vs. keeled), hypanthia smooth and glabrous at the apex (vs. ribbed, covered with a “crown” of trichomes at the apex), 4-merous flowers (vs. 5-merous) with isomorphic stamens (vs. dimorphic), and 2-locular ovaries (vs. 4–5-locular).

Based on W. Ganev 1873, Microlicia tetramera was cited as “ aff. Microlicia ” in the checklist of Melastomataceae for Rio de Contas, Bahia , Brazil ( Santos & Silva 2005).

Figures

FIGURE 5. Selected photos of species compared to new taxa described in this study. A–B. Marcetia nummularia. A. Habit. B. Flower close up. C. Microlicia obovatifolia, flower close up. D. Microlicia cryptandra, flowering branch. E. Microlicia noblickii, flower close up. F. Microlicia parvula, flowering branch. G. Microlicia sulfurea, flowering branch. H. Microlicia juniperina, flowering branches. Photos: A–B, E, H, by R. Pacifico; C–D, F, by F. Almeda; G, by J.A. Siqueira Filho (HVASF herbarium).

FIGURE 15. A. Brazil with Bahia state highlighted. B. Bahia with the study area outlined (dashed line). C. Distributions of Microlicia barbata, Microlicia prostrata, and Microlicia tetramera in the Chapada Diamantina, Bahia, Brazil.

FIGURE 22. Microlicia tetramera, photos of living plants. A. Habit. B. Branches terminating in flowers at anthesis. C. Flower in lateral view. D. Flower in frontal view. E. Fruiting branch. All photos by R.Pacifico. Voucher: R. Pacifico et al. 642.

FIGURE 23. Microlicia tetramera, photos of dry specimens. A. Habit. B. Detail of branchlet. C. Leaf adaxial surface. D. Leaf abaxial surface. E. Floral bud. F. Petal adaxial surface. G. Stamen. H. Capsule enveloped by the hypanthium. I. Capsule after the hypanthium fell away. J. Seed in lateral view. Scale bars:A, 2 cm; B–D, F, 2 mm; E, G–I, 1 mm; J, 0.2 mm. Vouchers:A, W. Ganev 1873; B–J, R. Pacifico et al. 642.

FIGURE. 3. A. Brazil with Bahia state highlighted. B. Bahia with the study area outlined (dashed line). C. Distributions of Marcetia auricularia, Marcetia santosiae and Marcetia unguiculata in the Chapada Diamantina, Bahia, Brazil.