Myrcia truncata Sobral (2012: 42)

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

21. Myrcia truncata Sobral (2012: 42) ( Figures 28 and 55 )

Type:— BRAZIL. Bahia: mun. Amargosa, serra do Timbó , mata do centro Sapucaia , 13º10’00’’S, 39º09’00’’W, 12 October 2007 (fr.), Paixão 1256 (holotype CEPEC!, isotype BHCB [image!])

Tree 3–4 m high. Epidermal peeling absent in immature parts; trichomes brown, 0.1–0.2 mm long. Twig when immature brownish (when dry), flattened, not keeled, cortex smooth; mature twig cylindrical, glabrescent; branching not seen, internode ca. 10 cm long; cataphyll not seen, cataphyll scars present in all internodes; bud at the terminal node not seen. Leaf discolorous, coriaceous, blade 31.5–33.0 × 10.5 cm, ovate, apex acute, base rounded or truncate, margin plane, secondary veins 8.0– 10.1 mm apart, held at an angle of 60° relative to the midvein, two marginal veins, the first 3 mm and the second 1 mm from the margin, tertiary veins conspicuous; adaxial surface glabrous at maturity, midvein sulcate in the first half and flat in the second half, secondary veins slightly raised, pellucid dots slightly conspicuous, more than 15 per mm 2; abaxial surface puberulent or glabrescent at maturity, midvein raised, secondary veins raised, pellucid dots slightly conspicuous, less than 5 per mm 2; petiole 1 × 3 mm, canaliculate, glabrous at maturity. Inflorescence 10.0–11.5 × 9–11 cm, pyramidal, axillar at the terminal node, rachis puberulent, four branching at the base, first internode of central rachis 4.0 mm wide, semicylindrical to flattened, distal internodes flattened, opposite branching, 3–5 branching per node, epidermal protrusion present at the nodes (usually absent in the apical branches); cataphylls at the base of the central rachis, 4 × 4 mm, ovate, externally glabrous, internally glabrous. Bract deciduous, not seen. Pedicel not seen. Bracteole deciduous, not seen. Floral bud not seen. Hypanthium ca. 1 mm extending above the summit of the ovary, not tearing at anthesis, externally puberulent, internally glabrous; calyx 5-merous, lobes 0.8–1.5 × 1.0– 1.2 mm, distinct from the hypanthium, deciduous, depressed ovate, concave, apex rounded, base truncate, externally and internally puberulent; petals not seen; stamens not seen; ovary not seen, style 4 mm, glabrous, stigma punctiform, papillose. Fruit green when immature, 10 × 11 mm, depressed globose or globose, base rounded (sometimes attenuate), glabrous; seeds 1.

Distribution and Habitat:— Myrcia truncata is found in the understory of submontane to montane rainforest in southern Bahia (Atlantic Forest domain). It is a rare species only found in the municipalities of Amargosa and Wenceslau Guimarães ( Figure 28 ).

Phenology:— It was collected with fruits in March and May. Flowers and mature fruits were not seen.

Conservation Status:— The species has an Area of Occupancy of 8 km 2 and is recorded in only two localities. Moreover, Atlantic Forest of southern Bahia has been extensively deforested in the last decades ( Landau et al. 2008). Thus, Myrcia truncata is considered as Endangered (EN, criteria B2a, biii; IUCN 2001).

Discussion:— Myrcia truncata shares large leaves with Myrcia insigniflora , the difference being that leaves in M. truncata are discolorous with rounded to truncate base and calyx lobes are deciduous and distinct from the hypanthium tissue. The thick and vinaceous twig (when dry) is characteristic, but is shared with M. insigniflora and Myrcia plusiantha .

Available illustrations and images:— Sobral et al. (2012).

Additional specimens examined:— BRAZIL. Bahia: Mun. Wenceslau Guimarães, 13 ° 34’48”S, 39 ° 41’24”W, 11 March 2013 (fr), E.J.Lucas 1189 (K!) . Total: 1 specimen .

Final remarks

This study presents a taxonomic revision of Myrcia sect. Sympodiomyrcia , a section of Myrcia that was recently the target of a phylogenetic study ( Santos et al. 2016a). Twenty one species are recognized in Myrcia sect. Sympodiomyrcia , representing 55 names and 30 basionyms. The difficulties in finding well-defined characters with low intraspecific variation for defining species are clear throughout this treatment. When variation exists, the characteristics rarely entirely excludes all other species. Methodological limitations include scarcity of collections from some species and regions, making complete understanding of morphology and distribution difficult. However, despite difficulties regarding the complex taxonomy of Myrcia ( Bentham 1869, McVaugh 1968, Landrum & Kawasaki 1997), the wide analysis of herbarium collections together with a bibliographic revision provide a satisfactory arrangement of the taxonomy of this group.

This is the first time that a complete taxonomic revision of a group inside Myrcia is published since Berg’s works with American and Brazilian Myrtaceae ( Berg 1855 –1856, 1857–1859, respectively; but see Nic Lughadha 1997). However, the number of species covered by the present work is a small fraction of the nearly 800 species of Myrcia (Lucas et al. 2011, WCSP 2018). More taxonomic studies of Myrcia are imperative and demand urgency, due to anthropogenic impact in most of Myrcia distribution and the expected loss of species.

Figures

FIGURE 28. Distribution of Myrcia insigniflora (squares), Myrcia mutabilis (circles) and Myrcia truncata (triangles). Continuous lines represent South American country and Brazilian state boundaries. The grey gradient represents elevation.

FIGURE 55. Images of representative specimens of Myrcia sect. Sympodiomyrcia species: Myrcia truncata (holotype: Paixão 1256 [CEPEC]).