Thinouia silveirae H. Medeiros, 2025

Medeiros, Herison, Acevedo-Rodríguez, Pedro, de Carvalho Lopes, Jenifer & Forzza, Rafaela Campostrini, 2025, Taxonomic revision and phylogenetic relationships of Thinouia (Sapindaceae), a neotropical genus, PhytoKeys 252, pp. 207-273 : 207-273

9. Thinouia silveirae H. Medeiros sp. nov.

Figs 17 , 18 , 19 B

Diagnosis.

Thinouia silveirae is most closely related to T. myriantha but differs from the latter by its mericarps with lenticular locule that are flat at the base, the pubescent epicarp and the densely villous locule cavity with capitate trichomes, and the petal appendage adnate to the marginal portion (vs. mericarps with slightly flattened locule; epicarp glabrous, locule cavity sparsely pilose or glabrous with scattered capitate trichomes, and petal appendage adnate to the basal portion).

Type.

Brazil. Acre • Mun. Xapuri. Ramal que dá acesso a pousada do Seringal Cachoeira , 9 Jul 2021, H. Medeiros, C. G. Silva and M. H. Oliveira 4496 (holotype: RB!, isotypes: INPA!, NY!, SPF!, RON!, UFACPZ!, US!) .

Description.

Tendrilled liana, 10–15 m long; stem 3–5 cm diam., cylindrical, striate, tomentose, glabrescent when mature, lenticels rounded or elliptic; cross-section simple. Leaves trifoliolate; stipules ca. 1 mm long, tomentose, triangular; petiole 5.8–12.4 cm long, terete or angular, striate, tomentose or pubescent; terminal petiolule 2–4.5 cm long, semiterete or terete, striate; lateral petiolules 0.7–1.9 cm long; leaflets with adaxial side glabrous or glabrescent, sometimes pubescent along veins, the abaxial side glabrescent, puberulous or pubescent; the leaflet secondary venation eucamptodromous but semicraspedodromous toward the apex; secondary veins 5–6 (7) pairs, alternate or subalternate, spacing irregular, with domatia on the abaxial side of secondary vein axils; intersecondaries present; tertiary veins alternate percurrent; margins entire or sparsely dentate, with 3–6 vestigial teeth reduced to inconspicuous glands; terminal leaflet 8.6–16.6 × 6–11.6 cm, elliptic-ovate or ovate, symmetrical or asymmetrical, the apex acuminate, sometimes emarginate, the base rounded; lateral leaflet 7.8–15.6 × 5.7–10 cm, elliptic or ovate, asymmetrical, the apex acuminate, sometimes rounded to retuse, the base truncate or slightly cordate. Thyrse umbelliform, axillary or terminal; solitary when axillary, 3.5–5.5 cm long, with a pair of circinate tendrils on distal portion of peduncle; peduncles 1.5–3.5 cm long; secondary peduncles 0.1–0.7 cm long; cincinni numerous, peduncle of cincinnus 1.7–4.7 mm long. Flowers 2.5–7.3 mm long, pedicel 1.2–3.5 mm long, pilose to villous; sepals ca. 0.7 mm long, connate at the base, deltate, abaxially villous, adaxially glabrous; petals ca. 0.5 mm long, obdeltoid to widely obtrullate, not clawed, villous; appendages ca. 0.9 mm long, longer than the petals, marginal and bifid, villous; nectary disc glabrous, annular. Staminate flower with stamens 8, ca. 2.7 mm long, the filaments villous at the base, the anthers ca. 0.5 mm long, papillose, glabrous or puberulous; pistillode ca. 0.5 mm long, villous. Pistillate flower with staminodes 0.8–1.2 mm long, villous; pistil ca. 1.5 mm long, villous. Fruits chartaceous, 4–6.1 × 2.5–3.9 cm; accrescent pedicel 2.6–5.3 cm long; stipe 4.2–9.4 cm long; seed locule lenticular but flattened at the base; epicarp pubescent at the locule, puberulous or pilose at the wing; cavity of seed locule densely villous, with capitate trichomes with uniseriate stalk and multicellular terminal cells. Seed ellipsoid 7.5–9.5 × 4.1–6.2 mm, glabrous.

Distribution and habitat.

Thinouia silveirae is known only from the southwestern Amazonian region, in the states of Acre and Rondônia, Brazil (Fig. 19 B ); in tropical and subtropical moist broadleaf forests. Flowering from June to July, and fruiting from July to September.

Etymology.

The specific epithet honors Dr. Marcos Silveira, professor and ecologist, at the Universidade Federal do Acre, who has made significant contributions to the floristic studies of Acre and SW Amazonia.

Notes.

Thinouia silveirae is strongly supported as sister to T. myriantha (Fig. 4 ) by our phylogenetic analyses of molecular data. In addition, both species share similar morphology, including elliptic to ovate leaflets, the presence of domatia, leaflet margins that are dentate to serrate, an annular and glabrous disc, and petal appendages that are longer than the petals (Fig. 5 ). Thinouia silveirae is differentiated from this close relative by its mericarps which have: (1) inflated, pubescent cocci that are flattened at the base; (2) wings that are puberulous or pilose; and (3) a densely villous seed locule cavity with simple and capitate trichomes.

Conservation status.

Thinouia silveirae possesses a broad EOO of 59,955.343 km 2 and an AOO of 12.00 km 2. Although this species is known only from a few collections, its conservation status is here treated as Least Concern (LC) due to its occurrence within two conservation units, the Reserva Extrativista do Cazumbá-Iracema in the state of Acre, and the Floresta Nacional do Jamari in the state of Rondônia.

Selected specimens examined.

Brazil. Acre • Mun. Sena Madureira, RESEX Cazumbá-Iracema , 31 Jul 2017, Medeiros et al. 2189 ( RB, SPF, UFACPZ, US) • Mun. Xapuri, Estrada para o Seringal Cachoeira , 8 Sep 2017, Medeiros et al. 2193 ( INPA, RB, SPF, UFACPZ) . Rondônia • Mun. Itapoã do Oeste, Floresta Nacional do Jamari , 28 Aug 2017, Medeiros et al. 2191 ( RB, RON, SPF, UFACPZ, US) .

Figures

Figure 4. Maximum clade credibility tree from a Bayesian analysis of the combined two-marker dataset for Thinouia and outgroups. Bayesian posterior probability values are indicated above the branches.

Figure 5. Maximum parsimony ancestral state reconstruction using Mesquite v. 3.70. Ancestral states are shown as the colors of the branches (see legend).

Figure 17. Thinouia silveirae H. Medeiros A vegetative branch B leaf showing abaxial surface C stem with lenticellate bark D stem cross-section E distal synflorescence F distal portion of synflorescence G mature fruits H staminate flower I pistillate flower [Medeiros 2191 (A – D, G) 4496 (E – F, H – I); photos by H. Medeiros].

Figure 18. Thinouia silveirae H. Medeiros A portion of flowering branch B leaf C indumentum on leaflets D staminate flower with portion of perianth removed showing nectary disc E pistillate flower F petal with bifid and marginal appendage, dorsal [abaxial] view G petal with bifid appendage, frontal [adaxial] view H stamen of staminate flower I fruit J mericarp K indumentum of epicarp L indumentum detail of locule cavity M capitate trichomes with uniseriate stalk and multicellular terminal cells from locule cavity N simples trichomes on locule cavity O seed P embryo (A – H from Medeiros 4496 I – P from Medeiros 2191). Illustration by Maria Alice de Rezende.

Figure 19. Distribution maps of Thinouia species A Thinouia paraguayensis and T. restingae B T. scandens and T. silveirae C T. tomocarpa and T. trifoliolata D T. ternata and T. ventricosa.