Myrcia proencana Villarroel & Gomes-Bezerra, 2015

Villarroel, Daniel & Gomes-Bezerra, Kadja M., 2015, New botanical discoveries of Myrtaceae from Bolivia and notes on Psidium hians, Phytotaxa 195 (2), pp. 163-170 : 163-166

Myrcia proencana Villarroel & Gomes-Bezerra , sp. nov. Type:— BOLIVIA, Santa Cruz, Prov. Velasco, Serranía de

Huanchaca, Campamento Huanchaca 2, 03 Dec. 2010, 14 º 31’30”S, 60º44’26”W, fl., J.R.I. Wood, D. Villarroel & M. Mendoza 27033 (Holotype USZ!, Isotypes K!, LPB!, UB!). Figures 1 , 2 .

Myrcia proencana , in a vegetative state is similar to M. torta , especially in leaf morphology when M. torta is very young or is sprouting after fire, and because both have a 3–locular ovary. However, M. proencana differs by a height less than 0.3 m ( M. torta reaches up to 1.8 m high), usually unbranched ( M. torta are branched shrubs or subshrubs), and because the inflorescences in M. proencana is an axillary dichasium, usually uniflorous (in M. torta the inflorescences is a panicle, with more than three flowers, axillary and terminal).

Subshrub up to 0.30 m tall, with a woody xylopodium; stems many, emerging from the base, usually unbranched, cylindrical in live plants, but flattened by drying, usually reddish or wine-colored, with glands visible when dry, pilose when young, glabrescent when mature, the trichomes simple and whitish. Leaves 3–5 x 0.3–0.6 (–8) cm, opposite, subopposite or distally alternate at the apex of the stem, usually oblanceolate, or long-oblong; apex acute, obtuse or rounded, the extreme tip inconspicuously mucronate; base cuneate and decurrent; chartaceous; upper surface glabrescent but pubescent on the midvein, the trichomes simple and whitish, the lower surface glabrous; glands visible and dispersed on both surfaces but more abundant in the lower surface, 2–4 per mm 2; upper surface glaucous-green, lower surface light opaque green; margin entire; midvein prominent on both surfaces; lateral veins ca. 7–10 pairs, brochydodromous forming a marginal vein 0.3 to 0.5 mm from the adge, the first pair ascending at an angle of ca. 30°, the others ca. 45°–50°, equally raised on both surfaces, branched exmedial intersecondary veins; petiole 0.8–1 mm long, canaliculate, pubescent or glabrescent, the trichomes simple and whitish. Inflorescence a dichasium, usually reduced to a single central flower only; one inflorescence per axil; peduncles (1–) 1.5–4.5 cm, wine–colored, with glands visible when dry, pilose or pubescent, the trichomes simple and whitish; bracts ca. 0.5–0.7 mm, deciduous (only observed in field), linear, pubescent on both sides, the trichomes simple and whitish; central flower sessile; lateral flowers with pedicels 2–3 mm, wine-colored, pilose or pubescent, the trichomes simple and whitish; bracteoles deciduous, not observed; floral buds 4–5 x 4–6 mm long, open, wide-pyriform to turbiniform toward the base, pubescent when young, glabrescent when mature; hypanthium ca. 2.5–3 mm long from the base ovary to base staminate disk, glabrous; calyx 5–lobed, the lobes 1.5–2 mm long and 2–3 mm wide at the base, deltoid or triangular, the apex acute, outside glabrous or glabrescent, inside with strigose hairs, the margin ciliate, wine-red in bud; petals 3–4.5 x 4–5 mm, orbicular or short-elliptic, glabrous on both surfaces, the margin not ciliate, with glands visible on both surfaces, wine-red in bud, pinkish or white when mature, sometimes with a red spot; stamens 126–132 arranged in 4 to 5 irregular whorls; filaments 4–7 mm long, glabrous; anthers <0.5 mm long, oblong; style 6–7 mm long, glabrous; stigma punctiform; ovary 3–locular; ovules 2 per locule. Fruits (immature) 3.5–5 x 3–4.5 mm, globose, glabrescent, with glands visible; seeds not observed.

Paratypes:— BOLIVIA. Santa Cruz, Provincia Velasco: Parque Nacional Noel Kempff Mercado [= PNNKM], Meseta de Huanchaca , Las Gamas , 14°48’52”S, 60°24’08”W, 01 Nov. 1995, fr, Killeen T. J. & Grinwood T. 7822 ( MO, USZ!) ; PNNKM, Meseta de Huanchaca, Campamento Huanchaca 2, 14°31’48”S, 60°44’44”W, 17 Nov. 2009, fl, Wood J. R. I. et al. 26463 ( K!, LPB!, UB!, USZ!) .

Phenology:—Some populations were observed and collected fertile in november and december. It appears that the reproductive phase is strongly related with the occurrence of fire and the arrival of the rains. Completely sterile populations were observed in unburned areas.

Etymology:—The specific epithet pays tribute to Carolyn Elinore Barnes Proença, professor of the Universidade de Brasília, who has studied the family Myrtaceae and the Cerrado vegetation, and promoted floristic, ecological and taxonomic studies in Brazil.

Affinities:— Myrcia proencana has a 3-locular ovary with 2 ovules per locule, leaves with reticulate venation and almost always one large gland per areole. These characters would position it within clade 6 of the Myrcia s.l. genus (sensu Lucas et al. 2011).

The species vegetatively most similar to M. proencana is M. torta De Candolle (1828: 250) (clade 9 in the Myrcia s.l. genus), especially when M. torta is very young or is sprouting after a burning, due to the similarity of the morphology of their leaves. However, these two species can be clearly distinguished by a set of vegetative, reproductive and ecological characteristics. M. proencana is a subshrub up to 0.3 m high, usually unbranched, the apex of the branches pilose and reddish or wine-colored, grows in campo limpo úmido (open wet grassland) and campo sujo úmido (shrubby wet grassland) ( M. torta , is a shrub or subshrub, 0.4–1.8 m high, branched, apex of the branches glabrous and yellowish, grows in areas with well-drained soils); the leaves in M. proencana are usually oblanceolate or long–oblong, apex acute, obtuse or rounded, the extreme tip inconspicuously mucronate, base cuneate and decurrent, 7 to 10 pairs of secondary veins, petiole 0.8–1 mm long (in M. torta usually elliptical, rarely oblanceolate, apex acute to obtuse, not mucronate, base attenuate or cuneate, not decurrent, 12 to 20 pairs of secondary veins, petiole 1–5 mm long). The inflorescences in M. proencana is a dichasium axillary, usually reduced to a single central flower only (very rarely with 3–flowered), not terminal (in M. torta the inflorescences is a panicle, with more than three flowers, axillary and terminal); M. proencana has floral buds of 4–5 x 4–6 mm long, pubescent when young, glabrescent when mature (in M. torta the floral buds are 2–3 x 2.5–3.5 mm, glabrous). M. proencana grows in more open vegetation such as campo limpo úmido and campo sujo úmido, and M. torta is a species that grows in the campo sujo and cerrado sensu stricto, always well-drained soils.

A photograph of this species is in Wood (2011a) under the name Psidium ‘ especie nueva ’.

Habitat:— Myrcia proencana is a species that is distributed between 600 and 950 m alt. It grows in campo limpo úmido (wet open grassland) and campo sujo úmido (shrubby wet grassland), where it is common and relatively abundant, on sandy or stony soil on area with gentle slopes leading down to valleys with mata de galeria (gallery forests) or vegetação de vereda (seasonally inundated fields with palms of Mauritia flexuosa Linnaeus filius (1781: 454)). M. proencana is one of the first species that grows quickly after its habitat has been burned. Usually when the campo limpo úmido is not burned, it goes unnoticed under the dense canopy of herbaceous biomass, which is dominated by grasses that form a canopy of up to 1 m in height.

Distribution:— Bolivia: Santa Cruz. So far, Myrcia proencana is endemic to Bolivia, and is known only from the plateau of the Serranía de Huanchaca of Noel Kempff Mercado National Park (in the north of Santa Cruz Department). The records of the species are limited to only two areas of the plateau: 1) Huanchaca 2 (central region of the Serranía), and 2) Las Gamas (southern region of the Serranía).

Conservation status:—According to the IUCN (2011) criteria, this species should be categorized as Least Concern (LC), not because they are abundant or have a wide distribution, if not rather because their populations do not show any external threat, it is common within these patches of campo limpo úmido and campo sujo úmido, their habitat is legally protected under Bolivian law to be within a National Park, and that access is difficult even for botanists ( Wood 2011b).

Figures

FIGURE 1. Myrcia proencana Villarroel & Gomes-Bezerra (Wood et al. 27033) A. Habit; B. Leaf, leaf venation pattern, lower surface; C. Flower bud; D. Open flower; E. Immature fruit (Killeen & Grinwood 7822). Illustration: Eliana Calzadilla.

FIGURE 2. Myrcia proencana Villarroel & Gomes-Bezerra.A. Habit; B. Branch with buds and open flowers.