Myrcia exapata Sobral 2016, sp. nov.
Creators: name: Sobral, Marcos
name: Caliari, Cláudia P.
name: Gressler, Eliana
name: Mazine, Fiorella F.
name: Magenta, Mara
name: Viana, Pedro L.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Myrtales
Myrtaceae
Myrcia
Myrcia exapata

description: 2. Myrcia exapata Sobral, sp. nov.
Type:— BRAZIL. Rio de Janeiro: mun. Nova Friburgo, Reserva Ecológica Municipal Macaé de Cima, Nascente do Rio das Flores, 22 ° 00’S, 42°03’W, 6 March 1989, M. Peron et al. 773 (holotype RB!, isotypes MO, NY, SP). Figure 3.
This species is related to Myrcia ochroides in its inflorescence structure, from which it is distinguished by its larger, obovate and mostly glabrous blades (to 140 × 55 mm versus to 40 × 30 mm, elliptic or ovate and densely pilose at least when young in M. ochroides), and its larger flowers (flower buds to 8 mm vs. up to 5 mm); it also reminds in its calyx morphology Myrcia calycampa, differing through its leaves with relatively shorter petioles (the ratio blade length / petiole length 25–33:1 versus 8–18: 1 in M. calycampa), obovate blades (vs. elliptic to narrowly elliptic) with obtuse or slightly cordate bases constricted at the junction with the petiole (vs. acute or rarely obtuse, never constricted at the junction with the petiole), and inflorescences with peduncles to 50 mm, the branching restricted to the upper portion (vs. up to 10 mm, the ramification regular along the axis).
Trees 10– 15 m. Twigs complanate, when young with simple grey trichomes to 0.5 mm, the internodes to 15 × 3–4 mm. Leaves with petioles 3–6 × 2 mm, adaxially complanate and somewhat sulcate; blades lanceolate or obovate, 100–140 × 30–55 mm, 2.5–3.5 times longer than wide, the young ones with simple grey trichomes to 0.2 mm, the adult ones glabrous and dull on both faces; glandular dots 5 to 8/mm 2, about 0.1 mm in diameter, visible only when the blades are examined against light; apex acuminate for 6–10 mm; base obtuse or slightly cordate, constricted at the very junction with the petiole; midvein impressed adaxially and strongly raised abaxially; lateral veins 12 to 16 at each side, impressed or plane, scarcely visible adaxially and raised abaxially, leaving the midvein at angles 60–70°, intermixed with secondary fainter lateral veins; marginal veins one or sometimes two, respectively 1.5–2 and 0.2–0.3 mm from the margin, the margin itself with a yellowish thickening about 0.2 mm wide and somewhat revolute near the base. Inflorescences axillary, paniculiform, with one sessile apical flower, one or two times ramified, the ramifications dichasial, with up to nine flowers, the axis complanate, 50–60 × 3 mm, the peduncle to 50 mm, the secondary axes to 12 × 1 mm and the tertiary ones, when present, 5–7 × 1 mm; flowers with pedicels absent; bracteoles not seen, probably deciduous before anthesis; flower buds globose or obovate, 6–8 × 5 mm, dense and uniformly covered by simple grey trichomes 0.5–0.8 mm; calyx lobes five, pilose as the buds, unequal between them, triangular or widely triangular, 2.5– 3 × 3.5–4 mm; petals white, rounded to obovate, to 8 × 5–6 mm, adaxially glabrous, abaxially with scattered trichomes to 0.5 mm; stamens about 200, filaments to 5 mm, the anthers subglobose, 0.3 × 0.2–0.3 mm, the thecae asymmetrical and sometimes with one connectival gland; staminal ring to 6 mm in diameter, with grey trichomes to 0.2 mm; style to 6 mm, the stigma punctiform; calyx tube absent or to 0.5 mm deep; ovary with two locules and two ovules per locule. Fruits globose to elliptic, 10–12 × 10 mm, immature in the specimens examined; seeds not examined.
Distribution, habitat and phenology:—This species is presently known from three flowering collections from montane rainforests in the municipality of Nova Friburgo, in the southeastern Brazilian state of Rio de Janeiro, at about 1100 m elev.; flowers were collected in March, and immature fruits in August and September.
Conservation:—Although the known specimens were collected in a protected area, the Reserva Ecológica de Macaé de Cima, in the municipality of Nova Friburgo, the information available allow scoring it, according to IUCN criteria (IUCN 2001) as Endangered (EN), since it fits criteria B1 (extent of occurrence smaller than 5,000 km ²; the municipality of Nova Friburgo has 933 km ²; see IBGE 2015b), B1a (collected in no more than five locations) and B1b(iii) (projected decline of extent and quality of the habitat; see Barros 2006). Additionally, there are about 13,600 collections from the municipality of Nova Friburgo (CRIA 2015), resulting in an average of 14.5 collections/km 2, what can be considered a good sampling effort; considering this, the existence of only three gatherings of Myrcia exapata may be an additional evidence of its rarity.
Affinities:—This species is very singular in its inflorescence morphology, with a large peduncle with the ramifications restricted to its distal portion. It is here tentatively compared with Myrcia ochroides O. Berg (1857 –1859: 208), a species collected in northeastern Brazil, which bears inflorescences that remind those of M. exapata, but is clearly distinct in the features cited in the diagnosis. It may also be compared, due to its relatively large calyx lobes, to the Amazonian Myrcia calycampa Amshoff (1942: 153; for description see Berg 1855 –1856: 130, under Calycampe latifolia O.Berg; type image: P barcode 001615017), from which it is distinguished through the characters given in the diagnosis. The features of M. exapata match partially the species included in the informal “group 5” by Lucas et al. (2011), to which M. calycampa also belongs, due to its bilocular ovary, five free calyx lobes, pilose staminal ring and short calyx tube (in some species of the group absent).
Etymology:—The name is derived from the Greek verb for “deceive” or “escape from surveillance” alluding to the fact that this species was not recognized as belonging to Myrcia, having been cited as Myrceugenia kleinii D.Legrand (Legrand 1961: 306) in a floristic inventory of Macaé de Cima, a locality in Nova Friburgo (Barroso & Peron 1994).
Paratypes:— BRAZIL. Rio de Janeiro: mun. Nova Friburgo: Macaé de Cima, 22°00’S, 42 ° 03’W, 26 April 1988, G. Martinelli et al. 12455 (BHCB!, RB!); idem, 28 September 1989, M. Peron 889 (RB!).
description: Published as part of Sobral, Marcos, Caliari, Cláudia P., Gressler, Eliana, Mazine, Fiorella F., Magenta, Mara & Viana, Pedro L., 2016, Seven new southeastern Brazilian species of Myrcia (Myrtaceae), pp. 27-44 in Phytotaxa 247 (1) on pages 30-32, DOI: 10.11646/phytotaxa.247.1.2, http://zenodo.org/record/13676381