Stryphnodendron riparium Scalon, 2022

Scalon, Viviane Renata, Paula-Souza, Juliana De, Lima, Alexandre Gibau De & Souza, Vinicius Castro, 2022, A synopsis of the genus Stryphnodendron (Fabaceae, Caesalpinioideae, mimosoid clade), Phytotaxa 544 (3), pp. 227-279 : 265-267

31. Stryphnodendron riparium Scalon , sp. nov. ( Fig. 9 ).

— Type : BRAZIL. Amazonas, Rio Solimões, ca. 1km ao sul da Vila Careiro, 23 August 1973, C.C. Berg et al. 19711 (holotype INPA 43195 !, isotypes F!, K!, MG!, MO!, NY!, R!, RFA!)

= Stryphnodendron inaequale Benth. ( Bentham 1875: 374) , pro syn.

Diagnosis: Stryphnodendron riparium is similar to S. guianense , differing by its conical petiolar nectaries (vs. verruciform in S. guianense ), leaves with 4–7 pairs of pinnae (vs. 8-11 pairs), spikes 6.5–7cm long (vs. 8–18.5 cm long), yellow flowers (vs. pinkish), tubular corolla (vs. campanulate) and ovary usually white-tomentose, sometimes sparsely white-tomentose (vs. glabrous to white pulverulent, glabrescent).

Trees 10–12 m tall, branches lenticelate, lacking extrafloral nectaries, sparsely ferruginous-pulverulent, glabrescent, densely ferruginous-pulverulent at the apex. Leaves with petioles 3.5–7.5 cm long, sparsely ferruginouspulverulent, glabrescent, very sparsely yellow-pubescent only near the insertion of the proximal pair of pinnae, extrafloral nectary 1, inserted at 1.5–2 cm from the base of the petiole, ca. 2 × 1–1.5 mm, conical; pinnae 4–7 pairs, subopposite to opposite, the insertion of each pair spaced in 1.6–2.4 cm (or less, between the distal pair of pinnae); rachis striate, sparsely ferruginous-pulverulent and yellow-pubescent, glabrescent; extrafloral nectaries 1–3, inserted 0.5–3 mm below the distal pair of pinnae, ca. 1 × 0.5 mm, verruciform to verruciform with an elongated base; stipels deciduous, not seen; petiolules of 2nd degree ca. 1 mm long, the same color as the upper surface of the blade, yellowpubescent; leaflets 5–10 pairs, the proximal pair of pinnae bearing fewer leaflets; rachillae yellow-pubescent and very sparsely ferruginous-pulverulent, glabrescent, extrafloral nectaries 2–9, inserted at ca. 1 mm below the distal pair of leaflets (usually only the 1–3 proximal pairs of leaflets lack extrafloral nectaries), ca. 0.5 × 0.5 mm, verruciform; stipel deciduous, not seen; leaflets usually subopposite, opposite towards the apex of the rachis, very rarely alternate, blade asymmetrical, usually oblong-rhombic to oblong, sometimes ovate, rarely elliptic (especially the proximal pairs of leaflets), the distal pairs usually widely obovate, sometimes obovate, (7–)10–21(–25) × (5–) 6–13 mm, apex usually rounded to retuse, rarely truncate, sometimes emarginate at the distal pairs, margin sub-revolute, entire and pubescent, base asymmetrical, the proximal side usually obtuse, sometimes widely rounded, usually acute at the distal pairs, distal side usually acute, sometimes narrowly rounded, chartaceous, discolor, upper surface dark, glossy, subglabrous, lower surface lighter, opaque, usually subglabrous, sometimes sparsely puberule, unilateral tuft of trichomes on the lower surface of the leaflets present, usually prolonged up to the 3rd pair of secondary nerves, venation brochidodromous, the nerves weakly evident, only the midrib sulcate, the remaining nerves weakly prominent at the upper surface, evident and prominent at the lower surface. Inflorescences of simple thyrsi, whitish-yellow; cymulae of solitary to ternate spikes, spikes 6.5–7 cm long; bracts deciduous, not seen; peduncle 0.5–1.2 cm long, densely ferruginous-pulverulent, glabrescent, cylindrical; rachis nigrescent covered by a yellow-pubescent indumentum, cylindrical, ca. 1 mm thick. Flowers monoclinous and diclinous (only staminate seen), yellow; calyx tubular, apiculate, yellow-pubescent, ciliate, ca. 1 mm long; corolla ca. 2.5 mm long, tubular, petals fused up to 2/3 of its length, glabrous to subglabrous at the tube, the lobes puberule, acute, erect; stamens 3.5–4 mm long, anthers ca. 0.5 mm long, nectaries stipitate, conspicuous fold present at the dorsal side of the anthers, approximately the same size as the thecae; ovary usually white-tomentose, sometimes sparsely white-tomentose, shortly stipitate, stigma porate; prophylls deciduous, ca. 0.5 mm long, shellshaped, yellow-pubescent. Fruit a sessile nucoid legume, straight to slightly curved, flat-compressed with slightly prominent seeds, 5–8 × 1.2–1.5 cm, valves coriaceous, reddish-brown, ferruginous-pulverulent, glabrescent. Seeds 5–7, not seen.

Etymology: —The epithet refers to the habitat in which the species grows in areas seasonally subject to the rivers´ floods.

Remarks: —The name Stryphnodendron inaequale is based on an identification with Bentham’s handwriting on the label of the sample Riedel 543 at K. Though there is no known published description for this name, this author synonymized S. inaequale under S. microstachyum ( Bentham 1875, 1876), which led to a series of mistakes concerning the names applied to several Amazonian taxa morphologically similar to this species.A detailed analysis of the material named as S. inaequale showed that Riedel’s collection shows distinct features from the type of S. microstachyum , namely indumentum at calyx and corolla and the rachillae bearing extrafloral nectaries between almost all pairs of leaflets, among other details that led to the recognition of a distinct species S. riparium . This is yet another species belonging to the group of Amazonian multifoliolate taxa with medium-sized leaflets, whose diagnostic characters are listed on Table 5 .

Distribution and habitat: —This species is restricted to the Xingu-Madeira phytogeographic province, in periodically flooded forests near igarapés or dark water floodplains, or in graminous fields along the Solimões river. The height of the individuals is often described on the herbarium labels as “meters above water”, indicating that it is most commonly found in flooded areas.

Conservation: —Least Concern (LC) [AOO= 32.000 km 2, EOO= 188,840.452 km 2].

Phenology: —Specimens of this taxon were collected with flowers in August and September, with fruits in June (young fruits) and July

Additional specimens examined (paratypes): — BRAZIL. Amazonas : Borba , Rio Madeira , s.d., fl., Riedel 543 (K). Careiro , Ilha da Marchantaria, Rio Amazonas, 13 July 1999, fr., M.A.D Souza et al. 614 ( INPA) . Humaitá , Rio Madeira, 23 June 1936, fl., A. Ducke s.n. ( RB 35524 ) . Manacapuru , Lago do Calado, beira do lago, 16 April 1986, im.fr., F.M. Magalhães 292 ( INPA) . Autaz Mirim , Rosa Branca, 13 June 1973, fl., A. Loureiro et al. s.n. ( INPA 38837 ) . Paraná do Autaz Mirim , 21 April 1966, im.fr., W. Rodrigues & F. Mello 7777 ( RFA) . Paraná do Autaz Mirim , Lago do Caioe, 26 August 1973, fl., C.C. Berg et al. 19763 ( INPA, K, MO, NY, US) . Rio Solimões , Lago de Manacapuru (água preta), 08 October 1972, fl., O. Pires 219 ( RFA) . Pará : Almeirim, margem do Paraná do Amazonas, 4 September 1918, fl., A. Ducke 17295 (R) .

Figures

FIGURE 9. Stryphnodendron riparium Scalon.A. Detail of rachis with extrafloral nectary. B. Detail of inflorescence rachis. C. Detail of rachilla. with extrafloral nectary D. Detail of anther (dorsal view). E. Flowering branch. F. Leaflet (adaxial side). G. Leaflet (abaxial side). H. Detail of petiole with extrafloral nectary. I. Flower.