Myrciaria coimbrarum Villarroel & Lino-Villalba, 2025

Villarroel, Daniel, Lino-Villalba, Oriana A., Arroyo-Herbas, Liliana & Klitgaard, Bente B., 2025, A new species of Myrciaria and botanical novelties in the family Myrtaceae for Bolivia, Phytotaxa 701 (3), pp. 261-270 : 262-267

Myrciaria coimbrarum Villarroel & Lino-Villalba , sp. nov. ( Figures 1 and 2 ).

Type: — BOLIVIA. Santa Cruz, Provincia Chiquitos: Entre Chochís e Ipias, sobre la Carretera nueva, a ½ km al oeste de la cumbre, 17°57’07’’S, 60°22’37’’W, 407 m, 17 October 2007, fl, J. R. I. Wood, D. Villarroel & P. Pozo 23576 (holotype USZ!, isotypes K!, LPB!).

Diagnosis:— Myrciaria coimbrarum is similar to the subshrub form of M. cuspidata (see specimens: G. Hatschbach et al. 67293, FURB!; H.S. Irwin et al. 13626, NY!), differing by having leaf blade> 1.5 cm wide and with non-mucronate apex (vs. <1.5 cm wide and with mucronate apex), 2 flowers per inflorescence (vs. 4–6 flowers per inflorescence), mature fruit 2–2.5 cm in diameter (vs. <1 cm diam.) and with a circular scar left by the calyx tube of 4–5 mm diam. (vs. circular scar left by the calyx tube <2 mm diam.).

Description:— Subshrub 0.2–1 m tall, rarely a shrub up to 1.5 m tall; growing in scattered groups, generally connected by a horizontal woody xylopodium, with 2–4 stems arising from the base; when shrub, then with glabrous, smooth, gray stems with white spots and with coriaceous rhytidome detaching in longitudinal strips; branch apex terete and pilose, with simple, whitish trichomes up to 0.5 mm long. Leaves opposite-decussate, ascending; blades (2–) 2.5–4 (–4.5) long × (1–) 1.5–2 cm wide, usually elliptical, sometimes ovate; apex acute or cuneate, sometimes acuminate; base cuneate, acute or slightly rounded; texture chartaceous; when young, glabrescent and reddish to wine-colored on both surfaces, the margin entire and ciliated, the trichomes simple and whitish; when mature, glabrous and light green on both surfaces, margin not ciliate or sparsely so, repand and revolute (more evident when dry); glands visible and dispersed on both surfaces, 3–5 per mm 2; midvein pilose, slightly sulcate in the basal portion and becoming plane in the distal portion on adaxial surface, glabrous or glabrescent and prominent on the abaxial surface, the trichomes simple and whitish on both surfaces; venation brochidodromous, lateral veins 18–21 pairs, slightly prominent on both surfaces, ascending, leaving the midvein at angles 40°–45°; marginal vein up to 0.5 mm from the edge; petioles 3–4 mm long, canaliculate, pilose or glabrescent, the trichomes simple and whitish. Inflorescences racemiform, axillary, 1 inflorescence per axil, from basal to apical leaves of branches, sessile or with peduncles up to 0.5 mm long, with 2 flowers per inflorescence; bracts and bracteoles 1–1.2 mm long × 0.8–1 mm wide at base, concave, deltoid, glabrous or glabrescent and with glands visible on the outside, glabrous on the inside, the margin ciliate, sparsely ciliate or only with hairs at apex, the trichomes simple and whitish; the bracteoles persistent until the fruit; pedicels up to 1 mm long, glabrescent, the trichomes simple and whitish. Flower buds 2–3 mm long × 1 mm wide at the base and to 2 mm wide at the apex, obovate, glabrous, light green coloured; open flowers with calyx 4-lobed, 1.5–2 mm long and to 2 mm wide at the base, slightly concave, deltoid, the apex cuneate or obtuse, glabrous or glabrescent, the trichomes simple and whitish, light green coloured and with glands visible on both surfaces; petals 4-lobed, white, 1.5–2 × 1–1.5 mm, orbicular or short-elliptic, glabrous and with glands visible on both surfaces, the margin no ciliate; stamens 50–75, arranged in 2–3 irregular whorls; filaments 3–4 (–5) mm long; anthers ca. 0.5 mm long, oblong, basifixed, with an apical gland; hypanthium ca. 1–1.5 mm deep, glabrous; style 4.5–5.5 mm long, glabrous, the stigma punctiform; ovary 2-locular, 2 ovules per locule. Fruits 1.5–2 cm long × 2–2.5 cm in diameter, globose or wide elliptic, glabrous, light green-colored and pruinose when immature, when mature, initially yellow, after orange with reddish to vinaceous spots and finally dark purple, with a circular scar left by the calyx tube, 4–5 mm in diameter, usually with small fragments of the calyx tube; endocarp yellowish-whitish, sweet; seed usually 1, rarely 2, 0.8–1.2 × 0.5–1 mm, elliptic, testa membranaceous; embryo with 2 plano-convex cotyledons, without evident hypocotyl.

Paratypes:— BOLIVIA. Santa Cruz, Prov. Chiquitos : Serranía de Santiago de Chiquitos , zona del mirador, 18.1920°S, 59.3417°W, 846 m, 25 November 2008, fl., J. R. I. Wood & D. Villarroel 25551 ( K, LPB!, USZ!) ; Santiago de Chiquitos , zona de la pista, ca. 1.5 km al suroeste de la plaza, 18°20’54.37”S, 59°36’17.02W, 610 m, 15 November 2018, fl., D. Villarroel 5821 ( LPB, USZ!) ; 0.5 km al oeste de la comunidad Ramada, sobre el camino a Ipiás , 18°00’08.4’’S, 60°03’41.2’’W, 390 m, 01 March 2020, fr, D. Villarroel et al. 6032 ( K, LPB, USZ!) ; Prov. Cordillera: 0.5–1 km al sur del Fortín Suarez Arana, sobre el camino a Roboré , 18°40’04.7”S, 60°08’20.1”W, 280 m, 28 December 2021, fr., D. Villarroel & O. A. Lino-Villalba 6304 ( K, LPB, USZ!) .

Distribution, habitat and phenology:— Myrciaria coimbrarum is a subshrub or shrub that was recorded in the east and southwest of the department of Santa Cruz ( Bolivia; Map 1), in the municipalities of Roboré and San José de Chiquitos (Chiquitos province), and Charagua Iyambae (Cordillera province).

It grows mainly in the Abayoy vegetation formations [equalling Cerrado Chaqueño by Ibisch et al. (2003); Figure 3A ], which develop on sandy, acidic, deep and well-drained soils ( Navarro 2011, Villarroel et al. 2016b) and are composed of typical species of the Cerrado flora combined with some typical species of the Chaco ( Ibisch et al. 2003, Navarro 2011, Villarroel et al. 2016b). In this habitat it is distributed between 250–450 m elev., is locally frequent and abundant in areas with tree cover <30% (abayoy ralo, Villarroel et al. 2021). It also inhabits phytophysiognomies of the cerrado rupestre of the Serranía Chiquitana , between 600–850 m elev., although with lesser frequency [the phytophysiognomies follow Ribeiro & Walter (2008) and Villarroel et al. (2016b)].

The flowering of M. coimbrarum begins with the wet season (October or November). According to field collections and observations, flowering is highly correlated with fire. In burnt areas, individuals produce abundant and synchronous flowering (“ big bang ” blooming type; Gentry 1974), and, in unburnt areas, only some individuals flower and produce few flowers (“ modified steady state ” blooming type; Gentry 1974). The fruiting period occurs between December and March, being abundant if the flowering was of the “ big bang ” type or scarce and even non-existent if it was of the “ modified steady state ” type.

The relationship between fire and flowering patterns of M. coimbrarum was also reported for other Myrtaceae species in Bolivia, all with the same type of habit, these are: Eugenia michaelneei Villarroel & Faria (2016a: 253) , Myrcia lignosa Villarroel & Proença (2013: 261) and M. proencana Villarroel & Gomes-Bezerra (2015: 163) . It also happens in species of other families, such as Plantago pyrophila Villarroel & J.R.I.Wood (2011: 471) , Plantaginaceae ; Pfaffia jubata Martius (1826: 24) , Amaranthaceae ; and Chrysolaena desertorum (Mart. ex DC.) Dematteis (2007: 62) , Asteraceae ( Villarroel & Wood 2011; Villarroel & Proença 2013; Villarroel & Gomes-Bezerra 2015).

Etymology:— The specific epithet “ coimbrarum “ pay tribute to Germán Coimbra Sanz (father) and Diego Javier Coimbra Molina (son), who have worked tirelessly to rescue the traditional knowledge of the useful plants of eastern Bolivia.

Conservation status:—The distribution of M. coimbrarum is restricted to the department of Santa Cruz, Bolivia. It is known from four localities, two of which are present within conservation areas (Tucabaca Conservation and Natural Heritage Unit and Ñembi Guasu Conservation and Ecological Importance Area; Map 1).

MAP 1. Distribution of Myrciaria coimbrarum in the department of Santa Cruz ( Bolivia) in relation to conservation areas (ACIE. Area of Conservation and Ecological Importance; UCPN. Conservation and Natural Heritage Unit) and the areas burnt between 2010 and 2020. Burned surfaces based on Villarroel et al. (2021).

The extent of occurrence (EOO) of M. coimbrarum is 3,419.9 km 2; and the area of occupancy (AOO) 24 km 2. The habitat of the populations growing in the Tucabaca Conservation and Natural Heritage Unit does not present any anthropogenic threats, since it grows on rocky outcrops, serpentine soils or on shallow soils on the Serranía Chiquitana Precambrian Shield. However , the populations growing near the Santiago de Chiquitos community is seriously threatened by the expansion of the urban area.

The populations inhabiting the Abayoy vegetation, whether inside or outside the Ñembi Guasu Conservation and Ecological Importance (Map 1), are seriously threatened by the expansion of agriculture and livestock; and possibly also by the increase in the frequency of fires (although the species has a xylopodium and its sexual reproduction is highly related to fire, the increase in the frequency of fires could gradually reduce the post-fire recovery of the populations; Figure 3B and C ).

Therefore, according to the IUCN (2024) criteria B1ab(iii) + 2ab(iii), M. coimbrarum is Endangered (EN), with an EOO <5,000 km 2 and AOO <500 km 2, ≤5 localities (sub-criteria a) and a continuous decrease in its area of extension and/or habitat quality [sub-criteria b (iii)].

Use:— The region where M. coimbrarum grows is popularly known as “ zaraza ” or “ azaraza ”. The fruits are highly appreciated by people, since they are sweet, succulent, have a pleasant flavor and are easy to harvest (it is a subshrub that grows in patches; Figure 2I ). It is also a food source for livestock and horses ( Villarroel et al. 2020).

Notes and taxonomic affinities:— Myrciaria coimbrarum belongs to tribe Myrteae ,subtribe Pliniinae .Vegetatively it is similar to the subshrub form of M. cuspidata , an uncommon habit in this species and which was observed in the specimens collected in Brazil by G. Hatschbach et al. 67293 (FURB!) at ~ 1,000 m elev. (Fazenda Serra do Cabral, state of Minas Gerais) and H.S. Irwin et al. 13626 (NY!), at 1,200 m elev. ( Serra dos Cristais , state of Goias); both inhabiting grassland phytophysiognomies of the Cerrado biome, but more than 1,300 km southeast of the sites where M. coimbrarum specimens were collected.

However, despite the similarities in habit type and habitat, M. coimbrarum is significantly distinguished from M. cuspidata by the characters listed in the diagnosis.

Figures

FIGURE 1. Myrciaria coimbrarum Villarroel & Lino-Villalba. A. General habit (J.R.I Wood et al. 23576; Holotype). B. Leave (J.R.I Wood & D. Villarroel 25551; Paratype). C. Flowers and inflorescence (J.R.I Wood & D. Villarroel 25551; Paratype). Scale bar in B & C: 1 cm.

FIGURE 2. Photographs of Myrciaria coimbrarum. A. General habit. B. General habitat and horizontal woody xylopodium. C. Stems with leathery rhytidome that detaches in longitudinal sheets. D. Young leaves. E. Mature leaves, phyllotaxis decussate and unripe fruits. F. Flowers and inflorescence. G. Fruit. H. Fruit, endocarp yellowish-whitish. I. Fruits harvested for consumption. Photographs: D. Villarroel (A–D & F); O.A. Lino-Villalba (E); G.A. Parada (G & H); L.R. Peinado (I).

FIGURE 3. Photographs of the Abayoy vegetation, Ñembi Guasu Conservation and Ecological Importance.A. Abayoy vegetation without burning record. B. Abayoy vegetation burned in 2019. C. Abayoy vegetation burned in 2019 and 2020. Photographs: D. Villarroel (B); O.A. Lino-Villalba (A & C).