Myrcia tenuifolia

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

20. Myrcia tenuifolia (O. Berg 1857 –1859: 67) Sobral (2006: 136) ( Figures 5B , 48 and 54 )

≡ Aulomyrcia tenuifolia O.Berg. Type:— BRAZIL. Bahia: Ilhéus, 1835 (fl.), Blanchet 2321 (holotype HAL [image!], isotypes BM [two sheets]!, F!, G [three sheets]!, K!, LE!, MICH!, NY!, P [two sheets]!, W!)

Shrub to tree 2–19 m high. Epidermal peeling present in immature parts; trichomes brown, light brown to white (rarely ferruginous), 0.1–0.2 mm long. Twig when immature brownish or straw-like (when dry), flattened, not keeled, with scattered trichomes to glabrous; mature twig greyish (when dry), cylindrical, cortex slightly cracked, glabrescent to glabrous; branching sympodial, 2–6 branches per node, epidermal protrusion present at the node, internode (1.5) 3.5– 15.5 cm long; cataphyll scale-like to foliaceous, 2–25 × 2–4 mm, present in all internodes, early deciduous, adnate, narrowly elliptic or ovate, externally glabrous; terminal node with central a bud developed, puberulent, lateral ones undeveloped. Leaf concolorous or discolorous, chartaceous, blade 5.5–16.5 × 2.0– 8.5 cm, elliptic or ovate, apex caudate, acuminate or acute, base attenuate, cuneate or obtuse, margin plane, secondary veins 2.5–7.0 mm apart, held at an angle of 55–84° relative to the midvein, two marginal veins, the first 1–3 mm and the second 0.1–1.0 mm from the margin, 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 slightly raised or inconspicuous, pellucid dots conspicuous to inconspicuous, more than 15 per mm 2; abaxial surface puberulent or with scattered trichomes to glabrous when immature, glabrous at maturity, midvein raised, secondary veins raised, pellucid dots conspicuous to inconspicuous, from 5 to 15 per mm 2; petiole 5–13 × 1–2 mm, canaliculate (rarely semicylindrical), puberulent or with scattered trichomes to glabrous when immature, glabrescent to glabrous at maturity. Inflorescence 2.0–15.5 × 1–6 cm, pyramidal, axillar at the terminal node (rarely at the subterminal node), terminal dichasia usually with three flowers, 12–172 flowers, rachis pubescent, puberulent or with scattered trichomes, 2–15 branching at the base (sometimes with vegetative branches), first internode of central rachis 1.0– 2.5 mm wide, semicylindrical to flattened, distal internodes flattened, opposite branching (rarely subopposite), 2–5 (rarely 6) branching per node, epidermal protrusion present at the nodes (usually absent in the apical branches). Bract 0.4–1.2 × 0.2–0.8 mm, deciduous, ovate or depressed ovate, concave, apex acuminate to obtuse, base truncate, adaxial surface glabrous, abaxial surface puberulent to glabrous. Pedicel 0–2.4 mm long, cylindrical, pubescent, puberulent to glabrous. Bracteole 0.4–0.8 × 0.2–0.4 mm, deciduous, ovate, concave, apex acuminate or acute, base truncate, adaxial surface glabrous, abaxial surface puberulent to glabrous. Floral bud 2–4 × 1–3 mm, clavate, sometimes with a small constriction above the bracteoles. Hypanthium 0.8–1.2 mm extending above the summit of the ovary, not tearing at anthesis, externally puberulent to glabrous, pellucid dots conspicuous (rarely inconspicuous), internally glabrous; calyx 3–5-merous, lobes 0.6–1.6 × 0.6–1.4 mm, distinct from the hypanthium, deciduous, depressed ovate or widely depressed ovate, concave, apex rounded, base truncate, externally puberulent or with scattered trichomes to glabrous, internally puberulent to glabrous; corolla 3–5-merous, petals light brown to white, 0.8–1.6 × 0.8–1.6 mm, depressed ovate to very widely ovate, concave, apex rounded, base truncate, externally and internally puberulent or with scattered trichomes to glabrous; staminal ring 0.2–0.4 mm wide, glabrous, stamens 42–81, filament 1.2–4.8 mm long, glabrous, anther 0.24–0.40 × 0.16–0.40 mm, square, oblong or transversely oblong; ovary 0.4–1.0 × 0.8–1.6 mm, 2-locular, each locule with two ovules, style 3.8–7.4 mm long, glabrous, stigma punctiform, papillose. Fruit green when immature, reddish at maturity, 6–10 × 5–13 mm, depressed globose or globose, base rounded, glabrous, remnants of calyx lobes present or not; seeds 1–2.

Distribution and Habitat:— Myrcia tenuifolia occurs in lowland rainforest in the Atlantic Forest domain, from central-northern Espírito Santo to southern Bahia (perhaps Rio de Janeiro). It is also recorded in montane rainforest (Santa Teresa region) ( Figure 48 ). The species usually inhabits forest understory.

Phenology:— It was found in flower from September to December and fruits from July to September and in March to April (mature fruits in April).

Conservation Status:— The species seems to have a relatively wide distribution (Extent of Occurrence ca. 47,900 km 2), but the scarce records led to a small Area of Occupancy (32 km 2). Moreover, the species is recorded from less than 10 locations and only two protected areas (the “Reserva Natural Vale” and the “Reserva Biológica Augusto Ruschi”, both in Espírito Santo state). Lowland forest in Bahia and Espírito Santo states, its main area of occurrence, has been deforested and is under strong anthropogenic impacts ( Landau et al. 2008). Thus, Myrcia tenuifolia is classified as Vulnerable (VU, criteria B2a, biii; IUCN 2001).

Discussion:— Myrcia tenuifolia is characterized by the scanty indumentum; sympodial branching with many branches (as in Myrcia mutabilis ); cataphyll scars present at all internodes; large and chartaceous leaves; inflorescence with many branches at the base ( Figure 5B ) and 3–5 apical branches per node, and clavate floral buds. It is similar to M. mutabilis differing chiefly in the chartaceous leaves, the conspicuous venation on the adaxial surface and the clavate floral bud (see discussion in M. mutabilis ).

There are two specimens of Myrcia tenuifolia (Blanchet 85, 2325 [P]) from the municipality of Ilhéus (Bahia state) that have reticulate venation and vinaceous twigs (when dry), features that resemble Myrcia plusiantha . However, the specimens have many branches at the base of the inflorescence and clavate floral buds, a combination of features only found in M. tenuifolia . Specimens from Linhares (Espírito Santo state) have smaller leaves and resemble Myrcia bicolor , but the multiple vegetative and reproductive branching place them in M. tenuifolia .

Available illustrations and images:— None found.

Additional specimens examined:— BRAZIL. Bahia: unknown municipality, 25 November 1937 (fl), G. Bondar 2514 ( SP!) ; unknown municipality, 1840 (fl), Blanchet 2418 (G!); unknown municipality, no date (fl), Blanchet 115 (BM!, P!); unknown municipality, no date (fl), Blanchet 85 (P!). Mun. Ilhéus , 1838 (fl), Blanchet 2325 (F!, G!, K!, P!, W!). Mun. Ipiaú , 29 October 1970 (fl), T.S.Santos 1223 (CEPEC!, ICN!, MICH!) ; ibidem, 26 October 1970 (fl), T.S.Santos 1195 (CEPEC!, MICH!, RB!). Mun. Itabuna , 300 m, 28 October 1983 (fl), R.Callejas 1573 (CEPEC!, NY!, RB!, SP!) . Espírito Santo: Mun. Conceição da Barra , 18 ° 35’36”S, 39 ° 43’56”W, 9 September 1992 (fr), O.J.Pereira 3830 ( RB!) . Mun. Linhares, Reserva Florestal da CVRD, 25 April 1983 (fr), D.A.Folli 443 (BHCB!, CVRD!) ; ibidem, 26 October 1982 (fl), I.A. Silva 357 (BHCB!, CVRD!, RB!, UEC!) ; Reserva Natural Vale , 17 March 2004 (fr), D.A.Folli 4768 (CVRD!, SPF!) ; ibidem, 34 m, 19 ° 14’50”S, 39 ° 57’41,5”W, 17 November 2011 (fl), M.F. Santos 747 (BHCB!, K!, NY!, RB!, SPF!, UB!) . Mun. Santa Teresa , 9 August 2001 (fr), L.Kollmann 4306 (BHCB!, MBML!) ; ibidem, 4 September 2001 (fl), L. Kollmann 4486 (BHCB!, MBML!) ; 550 m, 16 July 2003 (fr), A.M. Assis 957 (MBML!, SPF!) ; Reserva Biológica Augusto Ruschi , 920 m, 19 December 2002 (fl), R.R.Vervloet 1590 (MBML!, SPF!) . Rio de Janeiro (?): Castel Novo , 1821 (fl), Riedel 515 (K!, LE!, S!, W!). Total: 18 specimens .

Figures

FIGURE 5. Inflorescence of Myrcia sect. Sympodiomyrcia. A. Myrcia bicolor, sympodial branching at the base of the inflorescence, with terminal dichasia (Ávila 388 [SPF]). B. Myrcia tenuifolia, multiple branches at the base, including also vegetative branches (Santos 1223 [ICN]). C. Myrcia rupestris, inflorescence with one branch per axillary node, terminal dichasia present (Santos 640 [SPF]). D. Pyramidal inflorescence of Myrcia plusiantha (Barbosa 931 [SPF]). E. Corymbiform inflorescence of Myrcia densa (Santos 813 [SPF]). F. Umbelliform inflorescence of Myrcia mucugensis (Kral 75641 [SP]). Scales: C=1 cm; F=5 mm.

FIGURE 48. Distribution of Myrcia subcordata (circles) and Myrcia tenuifolia (squares). Continuous lines represent South American country and Brazilian state boundaries. The grey gradient represents elevation.

FIGURE 54. Images of representative specimens of Myrcia sect. Sympodiomyrcia species: Myrcia tenuifolia (Silva 357 [SPF]).