Myrcia bicarinata

Santos, Matheus F., Lucas, Eve & Sano, Paulo T., 2018, A taxonomic monograph of Myrcia sect. Sympodiomyrcia (Myrteae, Myrtaceae), Phytotaxa 380 (1), pp. 448-450 : 448-450

3. Myrcia bicarinata (O. Berg 1857 –1859: 118) D. Legrand (1961: 298) ( Figures 6B , 13 and 14 )

≡ Aulomyrcia bicarinata O.Berg. Type :— BRAZIL. No date (fl.), Sellow s.n. (lectotype P [barcode P00161322]! designated by Santos et al. (2016b), isolectotypes BM [barcode BM000953638]!, BR [barcode 523627]!, F [herbarium number 936906]!, K [barcode K000331712]!, LE [barcode LE00007024]!, P [barcode P00161321]!, U [barcode U0005096] [image!], W [herbarium number W0033195]!)

= Aulomyrcia rufa O. Berg (1857 –1859: 65). Myrcia rufa (O.Berg) N. Silveira (1985a: 66) . Type:— BRAZIL. No date (fl.), Sellow s.n. (lectotype K [barcode K000344213]! designated by Santos et al. (2016b), isolectotypes BM [barcode BM001125211]!, BM [barcode BM001125212]!, BR [barcode 526010]!, F [herbarium number 936902]!, LE!, P [barcode P00161101]!, P [barcode P00161102]!, W [herbarium number W0037071]!)

Shrub to tree 2–6 m high. Epidermal peeling present in immature parts; trichomes brown or light brown (rarely ferruginous), 0.1–0.4 mm long. Twig when immature brownish (when dry), flattened, keeled, with scattered trichomes; mature twig greyish (when dry), cylindrical, cortex slightly cracked, glabrous; branching monopodial(rarely sympodial), 2–4 branches per node (rarely more than three), epidermal protrusion absent at the nodes (present just when branching is sympodial), internode 1.3–6.5 cm long; cataphyll scale-like 2 × 2 mm, usually present only at the basal internode of a new branch, early deciduous, free, very widely ovate, externally and internally glabrous; terminal node with central bud developed, pubescent, lateral ones undeveloped. Leaf concolorous, chartaceous, blade (2.4)3.5–9.4 × (0.8) 1.3–4.8 cm, narrowly elliptic to widely elliptic, ovate, narrowly obovate or obovate, apex acute to rounded, base cuneate to rounded, margin plane, secondary veins 2–6 mm apart, held at an angle of 60–80° relative to the midvein, marginal vein 1.0– 1.5 mm from the margin (rarely two), tertiary veins conspicuous; adaxial surface with scattered trichomes to glabrous when immature, glabrous at maturity, midvein sulcate in the first half and flat in the second half, secondary veins flat or inconspicuous (rarely raised), pellucid dots conspicuous to inconspicuous, less than 5 to more than 15 per mm 2; abaxial surface puberulent or with scattered trichomes to glabrous when immature, glabrescent to glabrous at maturity, midvein raised, secondary veins raised (rarely inconspicuous), pellucid dots conspicuous to inconspicuous, less than 5 to more than 15 per mm 2; petiole 4–10 × 1–2 mm, canaliculate, with scattered trichomes to glabrous when immature, glabrous at maturity. Inflorescence 2.5–6.0 × 1.5–3.5 cm, pyramidal, axillar at the terminal or subterminal nodes, terminal dichasia usually with lateral buds aborted, 7–45 flowers, rachis with scattered trichomes to glabrous, 1–5 branching at the base (sometimes with vegetative branch), first internode of central rachis 1 mm wide, cylindrical to flattened, distal internodes flattened, opposite branching (rarely subopposite), 2–3 branching per node, epidermal protrusion present at the nodes (usually absent in the apical branches). Bract 0.6–1.4 ×0.4–1.0 mm, deciduous, lanceolate to very widely ovate, concave, apex acuminate or acute, base truncate, adaxial and abaxial surfaces glabrous. Pedicel 0–3.2 mm long, cylindrical, glabrous. Bracteole 0.6–1.0 × 0.2–0.4 mm, deciduous, lanceolate or ovate, concave, apex acuminate, base truncate, adaxial and abaxial surfaces glabrous. Floral bud 2–4 × 1–2 mm, turbinate, sometimes with a small constriction above the bracteoles. Hypanthium 1.0– 1.2 mm extending above the summit of the ovary, not tearing at anthesis, externally glabrous (rarely with scattered trichomes), pellucid dots conspicuous, internally glabrous; calyx 4–5–merous, lobes 0.4–1.2 × 0.4–1.6 mm, distinct from the hypanthium, deciduous, depressed ovate to widely ovate, concave, apex obtuse or rounded, base truncate, externally with scattered trichomes to glabrous, internally puberulent or with scattered trichomes to glabrous; corolla 4–6–merous, petals light brown to white, 1.0–1.6 × 1.4–2.0 mm, depressed ovate to very widely ovate or widely obovate, concave, apex rounded, base truncate, externally with scattered trichomes to glabrous, internally puberulent or with scattered trichomes to glabrous; staminal ring 0.2 mm wide, glabrous, stamens 64–82, filament 2–4 mm long, glabrous, anther 0.16–0.32 × 0.16–0.40 mm, square, oblong or transversely oblong; ovary 0.8–1.2 × 0.8–1.6 mm, 2–locular, each locule with two ovules, style 4.8–6.4 mm long, glabrous, stigma punctiform, papillose. Fruit 5–7 × 7–8 mm, depressed globose or globose, base rounded, glabrous, remnants of calyx lobes present or not; seeds 1–3.

Distribution and Habitat:— Myrcia bicarinata is found in submontane to montane semideciduous forest (Minas Gerais, Paraná and São Paulo states) and rainforest (Rio de Janeiro state) of Atlantic Forest domain, and in riparian forests of Cerrado domain (Distrito Federal) ( Figure 14 ). It inhabits the forest understory along watercourses. Field work carried out in the municipality of Mogi-Guaçu (São Paulo) showed that the species can have high population density.

Phenology:— The species flowers from August to November. Fruits were found in March, June and October (mature fruits in March).

Conservation Status:— The Extent of Occurrence (near 300,000 km 2) of Myrcia bicarinata does not reflect its real extension, because its distribution is restricted to riparian forest and records are sparse along the distribution perimeter. The area of occupancy (48 km 2) is likely closest to its real distribution. Species habitats have been severely fragmented, although riparian forests are fully protected under Brazilian Forest Code. Furthermore, recent changes in Brazilian Forest Code decreased the area of protected riparian forest. For these reasons, M. bicarinata is classified as Endangered (EN, criteria B2a, biii; IUCN 2001).

Discussion:— The species is characterized by strongly flattened and keeled immature twigs, mainly monopodial vegetative branching, cataphyll scar present usually only at the basal internode of a new branch and terminal dichasia with aborted lateral flowers ( Figure 6B ). Immature inflorescences bear the small lateral bud flowers of the dichasium, which fall during inflorescence development. The protologue of Myrcia bicarinata indicates an ovary two or three locular ( Berg 1857 –1859), but it was only found two locular ovary, which is the norm of the group.

Sobral et al. (2015) considered Myrcia bicarinata as a synonym of Myrcia pulchra (= Myrcia subcordata ), but diagnostic features of M. bicarinata are not found in M. subcordata (see identification key). Moreover, the species occurs in different habitats and localities (except in the municipality of Poços de Caldas– Minas Gerais state). Myrcia costeira is the most similar species to M. bicarinata but the later differs by the leaf size, the venation usually conspicuous on the abaxial surface of leaf blade and the corymbiform inflorescence with only the central flower of the terminal dichasia (see identification key). In addition, the species are found in different localities and habitats.

Available illustrations and images:— None found.

Additional specimens examined:— BRAZIL. Unknown province/state, 1858 (fl), Weddell s.n. (G!). Distrito Federal: Mun. Brasília, 20 September 1978 (fl), E.P.Heringer 623 (IBGE!, NY!, RB!, UEC!); ibidem, 700–1000 m, 30 August 1964 (fl), H.S.Irwin 5732 (MICH!, NY!, UB!, US!); ibidem, 1060 m, 15 ° 52’28”S, 47 ° 51’0”W, 21 September 1982 (fl), J.B.Kirkbridge 4899 (UB!, US!); ibidem, 1100 m, 15 ° 52’0”S, 48 ° 0’0”W, 4 September 2000 (fl), E.S.G.Guarino 403 (BHCB!, SPSF!, UB!); Reserva Ecológica do IBGE, 15 ° 57’6”S, 47 ° 52’56”W, 17 August 1989 (fl), M.L.M.Azevedo 301 (IBGE!, K!, RB!). Minas Gerais: unknown municipality, 1864 (fl), Regnell 550 (P!, S!). Mun. Caldas, 1874 (fl), Mosén 882 (P!, S!). Mun. Juiz de Fora, 10 October 1979 (fl), L.Krieger s.n. (BHCB 124882, CESJ!, ESA!). Paraná: Mun. Jaguariaíva, 25 March 1968 (fr), G.Hatschbach 18974 (C!, MBM!). Rio de Janeiro: unknown municipality, 1816 (fl), Langsdorff s.n. (LE!). Mun. Teresópolis, Serra dos Órgãos , 10 October 1979 (fr), M.Sabino s.n. (CESJ 16775, MBM!, SPF!). São Paulo: Mun. Angatuba, 23 ° 29’50”S, 48 ° 20’0”W, 3 November 1997 (fl), L.C.Souza 128 (SP!). Mun. Itapecirica da Serra , 15 August 1998 (fl), W.Ribeiro s.n. (SP 330101!). Mun. Jundiaí, October 1825 (fl), Riedel 47 (LE!). Mun. Martinho Prado, Estação Ecológica Mogi-Guaçu (Fazenda Campininha), 6 October 1988 (fl), S.Romaniuc Neto 1113 (K!, MO!, SP!). Mun. Mogi Guaçu, 14 March 1988 (fr), L.Rossi 996 (K!, SP!); Estação Ecológica Mogi-Guaçu (Fazenda Campininha), 588 m, 22 ° 17’0”S, 47 ° 9’0”W, 10 March 2012 (st), M.F.Santos 849 (K!, RB!, SPF!, SPSF!). Mun. Piracicaba, 22 ° 36’12,6”S, 47 ° 36’5,4”W, 15 June 1993 (fr), K.D.Barreto s.n. (ESA 14874!). Total: 19 specimens.

Figures

FIGURE 6. A. Myrcia lenheirensis, three terminal dichasia with only the central flower (Forzza 3692 [SPF]). B. Myrcia bicarinata, terminal dichasia with aborted lateral flowers (indicated) (Heringer 623 [IBGE]). C. Flowers of Myrcia nitida, one flower (right) with bracteole in the regular position (indicated), and the other (left) with one “migrant” bracteole at the hypanthium (indicated) (Lombardi 4532 [SPF]). D. Turbinate flower bud of Myrcia subcordata (Messias 5 [RB]). E. Clavate flower bud of Myrcia bicolor (Carvalho 6829 [SPF]). F. Obovate flower bud of Myrcia insigniflora (Assis 83 [BHCB]). G. Cross section of flower of Myrcia subcordata after anthesis, showing the hypanthium (indicated) not torn and internally glabrous, and the narrow staminal ring above (Santos 842 [SPF]). H. Flower of Myrcia insigniflora after anthesis, with the hypanthium tearing vertically, adnate petals (indicated) and persistent (but dry) stamens (Santos 682 [SPF]). Scales: A, C, D, G and H=2 mm; B and E=1mm; F=3 mm.

FIGURE 13. Images of representative specimens of Myrcia sect. Sympodiomyrcia species: Myrcia bicarinata (Sabino s.n. [SPF 199788]).

FIGURE 14. Distribution of Myrcia bicarinata (squares) and Myrcia costeira (circles). Continuous lines represent South American country and Brazilian state boundaries. The grey gradient represents elevation.