Eugenia michaelneei Villarroel & Faria, 2016

Villarroel, Daniel, Faria, Jair E. Q., Belmont, Aléxia Moraes, Gomes, Sueli Maria & Proença, Carolyn E. B., 2016, New botanical discoveries in Eugenia (Myrtaceae) from Bolivia and Brazil, Phytotaxa 253 (4), pp. 266-274 : 267-270

Eugenia michaelneei Villarroel & Faria , sp. nov. ( Figures 1 and 2 ).

Type: — BOLIVIA. Santa Cruz: Prov. of Chiquitos, Santiago de Chiquitos, subida de la zona de la cueva hacia el filo de la serranía de Santiago de Chiquitos en dirección al valle de Tucavaca, 18.3382ºS, 59.5483ºW, 22 March 2009 (fr.), J.R.I. Wood, D. Villarroel & S. Renvoize 25873 (holotype USZ!, isotypes K!, LPB!, UB!).

Eugenia michaelneei is somewhat morphologically similar to E. sonderiana , especially in leaf morphology and inflorescence type. However, E. michaelneei differs by its height that is less than 0.4 m ( E. sonderiana is a tree or shrub to 1.5 m or higher); leaf blade with 5–8 pairs of secondary veins, 8–12 glands per mm 2, and glabrescent midvein on the abaxial surface ( E. sonderiana has 10–14 pairs of secondary veins, 2–5 glands per mm 2, and a pulverulent indumentum on the midvein on the adaxial surface, a characteristic considered typical of the species); and a 2-locular ovary with 8–11 ovules per locule ( E. sonderiana has a 2 or 3-locular ovary with 21–26 ovules per locule).

Subshrub up to 0.4 m tall, growing in patches up to 1 m radius, generally connected by a horizontal woody xylopodium; stems 1–4, arising from the base, usually unbranched or sparsely branched, cylindrical, when young reddish to wine-coloured, covered with whitish hairs, when mature grayish and glabrescent. Leaves 1.5–4.6 × 0.6–2.2 cm, opposite, inflexed, subsessile, elliptical to oblong; apex obtuse or rounded, sometimes acute or slightly acuminate; base obtuse or rounded; texture sub-coriaceous; upper surface and lower surface glabrous, the glands visible and dispersed on both surfaces but more abundant on the lower surface, 8–12 per mm 2; surfaces discolorous, upper surface glaucous green, lower surface light opaque green; margin entire; midvein biconvex and glabrous on the upper surface, prominent and glabrescent on the lower surface; lateral veins 5–8 pairs, brochidodromous, forming a marginal vein ca. 0.7–2 mm from the edge; petiole 0.8–1.5 mm long, slightly canaliculate, glabrescent, the trichomes simple and whitish. Inflorescence one per axil, racemose, umbelliform, subterminal and terminal, with 1–2 pairs of flowers per inflorescence, but usually only 1 pair reaching maturity; peduncle reduced or absent; bracts and bracteoles the same size, 0.6–0.8 × 0.7–1 mm, concave, persistent in the fruits, deltoid, glabrescent on both surfaces, the margin ciliate; pedicels 3–7 mm, glabrous or glabrescent; flower buds 3.5–4 × 3–3.5 mm, globose, glabrous, the apex reddish to wine-coloured; hypanthium ca. 1–1.2 mm long from the base of the ovary to the base of the staminal disk, pubescent; calyx 4-lobed, the lobes unequal, the outer pair 1.3–1.5 × 1.6–1.8 mm at the base, the inner pair 1.2–1.4 × 1.4–1.6 mm at the base, concave, deltoid or slightly orbicular, the apex acute, obtuse or rounded, both surfaces glabrous, the outer surface with visible glands, the margin ciliate, the bases internally reddish to wine-coloured (forming a reddish ring around the staminal disc); petals 4, white, equal, 3.5–4.5 × 3.5–4 mm, concave, orbicular, glabrous on both surfaces, with glands visible on the outer surface, the margin ciliate; stamens>100, arranged in 2–3 irregular whorls; filaments 3–5 mm long, glabrous; anthers 0.5–0.6 mm long, oblong, dorsifixed, with an apical gland; style 5.5–6.5 mm long (persistent in the fruits), glabrous, the stigma punctiform; ovary 2-locular; ovules 8–11 per locule. Fruits 5–7 × 5–6.5 mm, black when mature, globose or ellipsoid, glabrous; fruiting calyx lobe erect; seeds not observed.

Paratypes:— BOLIVIA. Santa Cruz: Provincia Chiquitos, on the N side of the Serranía de Chochís , W of La Abra, 11 October 2001, fl., J.R.I. Wood 17313 (K, HSB!, LPB; USZ!) ; Meseta de Chochís, zona del Portón , 18°06’52”S, 60°03’33”W, 650 m, 02 December 2013, fl., D. Villarroel et al. 2298 ( UB; USZ!) ; Santiago de Chiquitos , zona del mirador, en la cima de la meseta, 18°19’23”S, 59°34’20”W, 08 January 2015, fl./fr., D. Villarroel 5332 ( LPB, MO, UB, USZ!) .

Etymology:—The specific epithet pays tribute to Michael Harley Nee, who has significantly contributed to improving the knowledge of the Bolivian flora.

Phenology:—According to field observations, the reproductive phase of E. michaelneei is strongly related to the occurrence of fire and the arrival of the rains. When the habitat of the species has been burned, all individuals bloomed at the same time. These observations were made in October 2001 in the Meseta de Chochís, when all individuals in the population were with flowers. The same occurred in March 2009, in the Zona del Arco from Santiago de Chiquitos, when all individuals in the population had fruits. However, when the habitat had not been burned, some individuals produced a few flowers, less than 6 flowers per individual, with the majority in a vegetative state. This pattern was observed during the rainy season in September 2011, December 2013, and January 2015. All individuals flowering simultaneously in the burned areas fit the “ big bang ” blooming type ( Gentry 1974), i.e. blooming is short, continuous and synchronous. On the other hand, when the habitat has not been burned, the flowering pattern was that of a “ modified steady state ” ( Gentry 1974), with some individuals producing a few flowers. Similar patterns in the relationship between fire and flowering are reported by Villarroel & Proença (2013), and Villarroel & Gomes-Bezerra (2015) for other species of Myrtaceae in Bolivia, all with the same type of habit and habitat: Myrcia lignosa Villarroel & Proença (2013: 261) , M. proencana Villarroel & Gomes-Bezerra (2015: 163) and Myrciaria sp. nov. (D. Villarroel 2016, pers. comm.). Species of other families in the Bolivian Cerrado have these reproductive patterns too, such as Plantago pyrophila Villarroel & J.R.I.Wood ( Villarroel & Wood 2011: 471), Plantaginaceae ; Pfaffia jubata Mart. ( Martius 1826: 24), Amaranthaceae ; and Chrysolaena desertorum (Mart. ex DC.) Dematteis (2007: 62) , Asteraceae ( Villarroel & Wood 2011; Villarroel & Proença 2013; Villarroel & Gomes-Bezerra 2015).

Habitat:— Eugenia michaelneei grows in campo limpo (open grassland) and campo sujo (shrubby grassland) on well-drained soil, on the Meseta de Chochís and the Serranía de Santiago de Chiquitos between 650–1000 m elev. The plants apparently have preference for sandy soils ( Fig. 2a ).

Distribution:— Eugenia michaelneei is endemic to Chiquitos Province ( Bolivia), and is known only from the Meseta de Chochís to Santiago de Chiquitos in the Serranía de Chiquitos.

Conservation status:— Eugenia michaelneei should be considered as a Vulnerable (VU D2) species according to IUCN criteria (IUCN 2011). The occupation area of the species is less than 20 km 2, and its population is estimated in less than 1.000 individuals.

Affinities:—The species most similar to Eugenia michaelneei is E. sonderiana , mainly by the appearance and morphometrics of its leaves and flower buds, inflorescence type, and pubescent hypanthium. However, the two species can be clearly distinguished by the vegetative and reproductive characters ( Table 1).

Eugenia michaelneei , judging from the type of inflorescence, is part of Eugenia sect. Umbellatae O. Berg (1856) . In the phylogenetic classification proposed by Mazine et al. (2014), this new species is probably part of Eugenia clade 9, judging by the type of inflorescence, and especially by the flowers with very short bracts and calyx-lobes, persistent bracteoles, a 2-locular ovary, and many ovules per locule.

Eugenia michaelneei and E. sonderiana have some anatomical characteristics in common. In both species, the petiole is plane-convex and has a single vascular bundle, with the central region occupied by phloem. The leaf blades are hypostomatic, with unistratified epidermis, and with high stomatal density in the region located between the veins. The stomata are leveled, paracytic, and the guard-cells have a telephone shape. The mesophyll is dorsiventral, with two layers of palisade parenchyma. The spongy parenchyma has braciform cells, with idioblasts containing druses. The unique vascular bundle in the midvein is bicollateral, with a conspicuous sheath in both species. Glands (oil secretory cavities) are present in the petioles and mesophylls, and they have epidermal overlaying cells. The anatomical differences between the two species are presented in Table 2 and Figure 3 . Anatomical characters useful in the taxonomy of Myrtaceae have been explored by Johnson & Briggs (1984), Leon & Williams (2005) and Gomes et al. (2009), and in Eugenia in particular by several authors, more recently by Cardoso & Sajo (2004) and Villarroel et al. (2014b). In the present study, petiole and leave blade anatomy revealed many differences between the new species and its putative nearest relative ( E. sonderiana ), and contributed to their better circumscription. Leaf anatomy data has been used to reconstruct a cladogram of Myrtaceae ( Gomes et al. 2009) . The present work is an addition to the anatomical literature on Eugenia and perhaps in the future anatomical data can be useful to produce a cladogram for this genus.

Figures

FIGURE 1. Eugenia michaelneei Villarroel & Faria. a. General habitat (J.R.I. Wood et al. 25873). b. Fruit (J.R.I. Wood et al. 25873). c. General habitat and horizontal woody xylopodium (J.R.I. Wood 17313). d. Inflorescence (J.R.I. Wood 17313). e. flower but (J.R.I. Wood 17313).

FIGURE 2. Eugenia michaelneei Villarroel & Faria in the field (D. Villarroel 5332). a. Population on sandy soils. b. Individuals of the species. c. Individuals with inflorescence. d. reddish to wine-coloured circle around the staminal disc.

FIGURE 3. Anatomy of Eugenia species: petioles (A, C), and leaf blades (B, D–R). A–B, E, G–J, O–P. E. michaelneei Villarroel & Faria, Wood et al. 25873 (isotypes). C–D, F, K–N, Q–R. E. sonderiana O. Berg, J.E.Q. Faria 4650. A, C. Xylem (x): almost closed (A) and almost plane (C). B, D. Midvein: slightly convex (B), and prominent abaxially (D). E–F. Palisade parenchyma (pp): second layer shorter (E), and with the same high (F) than the first layer; glands (g). G, K. Epidermis: protoplasmatic projections (G, black arrow) in the external periclinal cell wall present or not (K). H, L. Stomata (open arrows). I–J, M–R. Adaxial (I–J, M–N), and abaxial (O–P, Q–R) epidermis: overlying cells (white arrows) associated with the glands with high (I–J, O–P) and low (M–N, Q–R) densities; high density of stomata (O–P, Q–R); trichomes (N, Q, lozenge arrows). A–H, K-L. Transversal sections. I–J, M–R. Paradermal sections. Scales: A–D, I, O, Q. 200 μm; E–F, J, M–N, P, R. 100 μm; G–H, K–L. 30 μm.