Inga micronectarium J.M. Fernandes, C.R.A. Soares & D.R. Silva, 2023

Fernandes, José Martins, Soares, Célia Regina Araújo & Silva, Dennis Rodrigues Da, 2023, Inga micronectarium (Leguminosae): A new species in the Amazon rainforest, Brazil, Phytotaxa 619 (3), pp. 232-240 : 234-238

Inga micronectarium J.M. Fernandes, C.R.A. Soares & D.R. Silva , sp. nov. ( Figs. 2–3 ).

Inga micronectarium differs from three similar species of Inga ( Table 1 , are they: Inga multijuga , Inga rubiginosa and Inga thibaudiana ) by the absence of lenticles on the young stems, stipules 1.8–2.3 × 2.5–4 mm, depressed-ovate, adpressed and persistent, stipitate foliar nectaries, stipe 0.4–1.2 mm long, head 0.3–0.6 mm long, 0.6–1 mm in diam., leaflets with a velutinous-sericeous adaxial surface, bracts 1.3–1.5 × 2–2.4 mm, depressed-ovate and persistent, and calyx densely sericeous-villous.

Type:— BRAZIL. Pará: Jacareacanga , 9°20’13” S, 56°46’34” W, 191 m alt., 19 October 2011, fl., C . R . A. Soares , D. L . Matos , C . Rodrigues , A . Mascarello & J . H . Piva 4355 (holotype HERBAM!, isotypes RB!, MG!, VIC!) .

Trees, 8–30 m tall. Young branches angulous, densely velutinous, ferruginous to golden, and the largest tector trichomes are 0.6–0.9 mm long. Stipules 1.8–2.3 × 2.5–4 mm, depressed-ovate, rarely narrowly triangular, adpressed, persistent. Leaves pinnate, pulvinus 4–7 mm long; petiole 1.8–5.1 cm long, cylindrical, velutinous; rachis 11.5–27.6 cm long, cylindrical, rarely marginate or alate on the portion above the last, penultimate and/or antepenultimate pairs of leaflets, 1–3(–4) mm wide, velutinous; terminal appendix 2.5–2.8 × 2–2.8 mm, ovate, persistent to semi-persistent; foliar nectary present between all pairs of leaflets, stipitate or rarely sessile, stipe 0.4–1.2 mm long, indumentum present, head 0.3–0.6 mm long, 0.6–1 mm in diam., cyathiform, circular; leaflets in (5–)6–7 pairs; leaflets of terminal pair 10.8–19.9 × 4.6–7.5 cm, elliptic, base oblique, apex short-cuspidate, acute to acuminate, secondary veins in 12–18 pairs; leaflets of basal pair 5–8.5 × 2.7–4.5 cm, ovate, base oblique, rarely obtuse, apex obtuse, acute or short-cuspidate, secondary veins in 10–14 pairs; adaxial surface short-velutinous to velutinous-sericeous, soft, abaxial surface densely velutinous-sericeous, soft, margins densely ciliate; venation eucamptodromous to brochidodromous. Inflorescences spiciform, grouped in axillary fascicles, 2–4, terminal pseudoracemes usually present, 3.5–8 cm long; peduncle 0.7–4.5 cm long, velutinous; rachis 1.8–5.4 cm long, congested, velutinous. Bracts 1.3–1.5 × 2–2.4 mm, depressed-ovate, persistent to semi-persistent. Flowers sessile, pentamerous; calyx open in bud, densely sericeous-villous, tubular, tube 3.5–6 × 2.4–3 mm, lobes 0.4–0.6 mm long, obtuse, irregular; corolla densely sericeous-villous, infundibuliform, tube 13–19 × 3.5–4.5 mm, lobes 2–3.5 mm long, irregular; androecial tube 17–26 mm long, included or exerted, stamens 45–67, 19–25 mm long, cream, anther 0.3–0.5 × 0.5 mm; nectariferous disc absent; gynoecium 1-carpelar; ovary 2.2–3 mm long, glabrous, style 45–49 mm long, glabrous, stigma discoid. Fruits a nucoid legume, 16–30.5 × 1.8–2.5 cm, linear, base obtuse, apex truncate, flat, margins narrow, 0.2 cm wide, transverse venation poorly visible, densely velutinous, golden; seeds not seen.

Additional material examined (Paratype):— BRAZIL. Mato Grosso:Aripuan„, Mineradora Dardanelos, Barragem, Córrego Arrainha , 10°04’01.55”S, 59°30’31.80”W, 143 m alt., 09 August 2019, fl., M.P.N. Pereira & C. Santana 943 ( HERBAM!); 10°04’05.75”S, 59°30’24.55”W, 174 m alt., 13 August 2019, fl., M.P.N. Pereira & F. Frota da Silva 962 ( HERBAM!) . Pará: Jacareacanga , 9°20’35”S, 56°46’34”W, 187 m alt., 09 December 2011, fr., C.R.A. Soares, E.S. Silva, M.F.D. Lima, N.F. Moura & J.B.M. Melo 4853 ( HERBAM!); Bragança, comunidade de Chaú, margem do afluente Chaú do rio Caeté , 1°00’47.1”S, 46°47’53.9”W, 28 February 2018, fr., L. Oliveira & J. Dergan 700 ( HBRA 10271 , photograph!) .

Etymology: —The specific epithet refers to the micro nectaries between all leaflet pairs.

Flowering and fruiting period: —The species has been collected with flowers in August and October and fruits in December and February.

Distribution and ecology: —The species is restricted to Mato Grosso and Pará, Brazil, where it grows in the Amazon biome in the Teles Pires and Juruena river basins ( Fig. 1 ). It occurs in dense terra firme forests, open vegetation in flooded forests and areas under natural regeneration in pastures, locally called pasto sujo.

Conservation:—The habitats in which this species has been found are under accelerated anthropogenic pressure, within the Arc of deforestation limits on Mato Grosso and Pará states, that according to Nogueira et al. (2007) this region comprises the “Arc of Deforestation” where there is selective logging, numerous forest fires, and the rapid and continuous conversion of natural areas into places for livestock, therefore, considering all the threats presented, the species is categorized in the Endangered: EN category according to the IUCN criteria ( IUCN 2012). Endangered—EN B1ab (i, ii, iii). Inga micronectarium is a species that has a fragmented distribution in the “Arc of Deforestation” region in the south and east of the Amazon. The AOO was estimated at 12km 2 (EN), these populations are under direct threats from mining and hydroelectric dams in the region. The EOO polygon of I. micronectarium presents higher values for inclusion of threatened status (estimated at 92,304,616 km 2 = LC—Least Concern) for B2 classifications. However, the EOO of I. micronectarium is located in regions with the highest rate of deforestation in the Amazon, in favor of agribusiness (Ribeiro et al. 2021).

Taxonomic comments:— Inga micronectarium is similar to Inga thibaudiana by the presence of a cylindrical, rarely marginate or alate leaf rachis, generally the same number of leaflet pairs, tubular calyx, and infundibuliform corolla ( Table 1 ), however Inga micronectarium can be distinguished by the young branches with a velutinous indumentum, depressed-ovate, adpressed, persistent stipules, leaves with 6–7 pairs of leaflets, stipitate (or rarely sessile) extrafloral nectaries with a stipe 0.4–1.2 mm long and head 0.6–1 mm in diameter and cyathiform, adaxial surface of the leaflets velutinous-sericeous, abaxial surface densely velutinous-sericeous, ciliate leaflet margins, and velutinous fruits. According to Pennington (1997), Inga thibaudiana has lenticellate young branches with an adpressed-puberulent to tomentose indumentum, ovate, caducous stipules, leaves with 4–6 pairs of leaflets, sessile extrafoliar nectaries with a secretory head that is 1.5–3.5 mm in diameter and patelliform or cyathiform, adaxial surface of the leaflets sparsely strigose or glabrous, abaxial surface sericeous-strigose or tomentose, and subglabrous fruits when mature.

TABLE 1. (Continued)

Inga micronectarium is similar to Inga multijuga because it generally has a cylindrical leaf rachis, the same number of leaflet pairs, and the exact shape of the leaflets, calyx, corolla, type of inflorescence, and size of the fruits ( Table 1 ). Inga micronectarium differs by the presence of densely velutinous young branches, depressed-ovate and persistent stipules, generally stipitate foliar nectaries with a head that is 0.6–1 mm in diam., velutinous-sericeous leaflets, persistent to semi-persistent bracts, a densely sericeous-villous calyx with a smaller tube that is 3.5–6 mm long, and densely velutinous fruits. However, according to Pennington (1997), Inga multijuga has lenticellate young branches with a curly pubescence, ovate to suborbiculate, caducous stipules, sessile foliar nectaries with a head that is 1–1.5 mm in diam., leaflets with a glabrous adaxial surface, except the midvein that has a curly pubescence, and abaxial surface with a curly pubescence on the midvein and lamina, caducous bracts, a sparsely pubescent calyx with a larger tube that is 4.5–10 mm long, and glabrous fruits.

Inga micronectarium is similar to Inga rubiginosa by the presence of velutinous young branches, a cylindrical leaf rachis, ovate basal leaflets, spiciform inflorescences, calyx that is open in bud, calyx, corolla and fruit that are usually the same length, and fruits with a velutinous indumentum ( Table 1 ). Inga micronectarium is distinguished by the absence of lenticels on the young branches, depressed-ovate, persistent stipules, stipitate (or rarely sessile) foliar nectaries with a stipe 0.4–1.2 mm long and head 0.3–0.6 mm long, 0.6–1 mm in diam. and cyathiform, presence of a persistent to semi-persistent, terminal appendix, leaves with (5–)6–7 pairs of leaflets, elliptic terminal leaflets, adaxial surface of the leaflets velutinous-sericeous, tubular calyx, and smaller corolla tube that is 13–19 mm long. However, according to Pennington (1997), Inga rubiginosa has lenticellate young branches, ovate, caducous stipules, sessile foliar nectaries with a 1.5–2 mm in diam., patelliform head, no terminal appendix, leaves with 3–5 pairs of leaflets, widely elliptic terminal leaflets, adaxial surface of the leaflets with only a velutinous midvein, cupuliform calyx, and larger corolla tube that is 18–29 mm long.

Figures

FIGURE 1. Distribution of Inga micronectarium in de Mato Grosso and Pará, Brazil.

FIGURE 2. Inga micronectarium. A. Branch with leaves and inflorescences. B. Indumentum of a young branch. C. Stipule. D–E. Foliar nectary. F. Leaf appendix. G. Indumentum of the adaxial surface of a leaflet. H. Indumentum of the abaxial surface of a leaflet. I. Floral bract. J. Flower. K. Ovary. L. Fruit. M. Indumentum of a fruit. A–K, based on C.R.A. Soares et al. 4355 (HERBAM), L, L. Oliveira & J. Dergan 700 (HBRA), M, C.R.A. Soares et al. 4853 (HERBAM). Illustrated by Reinaldo Pinto.

FIGURE 3. Inga micronectarium. Branches with leaves and inflorescences. Photograph: C.F.T. Barros.