Thinouia cazumbensis Medeiros, 2020

Medeiros, Herison, Lopes, Jenifer de Carvalho, Acevedo-Rodriguez, Pedro & Forzza, Rafaela Campostrini, 2020, A new species of Thinouia (Paullinieae, Sapindaceae) from the Amazon and its phylogenetic placement, PhytoKeys 165, pp. 115-126 : 115

Thinouia cazumbensis Medeiros sp. nov. Figure 2

Diagnosis.

The new species differs from Thinouia trifoliata by the 5-lobed floral disc, fruits with trichomes and basal petal appendages smaller than the petals, versus annular disc, glabrous fruits and marginal petal appendages larger than the petals.

Type.

Brazil. Acre. Sena Madureira. Reserva Extrativista do Cazumbá-Iracema, Núcleo Cazumbá, castanhal coletivo, floresta ombrófila aberta com bambu, 9°8'30"S, 68°56'23"W, 20 Jul 2018, H. Medeiros, M. Silveira & E.M. Soares 3401, (holotype RB!; isotypes: INPA!, SPF!, UFACPZ!, US!).

Description.

Tendrilled liana 6-8 m long; stem puberulent, with yellowish to whitish indumentum, lenticellate; cross section simple, cylindrical. Leaves trifoliolate; stipules ca. 2 mm long, hirsute-tomentose, linear triangular to lanceolate; petiole 2-8.5 cm long, canaliculate; petiolules of lateral leaflets 0.2-0.8 cm long; leaflets 7-14 × 3-9 cm, oblong to ovate- rhomboidal, apex acute, mucronate, margins entire to dentate-serrate, with 2-4 teeth reduced to inconspicuous glands, ciliate, base truncate, rounded to obtuse, sometimes cuneate on the distal leaflet, glabrous on both surfaces, domatia sometimes in the axils of abaxial secondary veins. Thyrses axillary, racemiform, ca. 8.5-16 cm long, peduncle 1.1-2.8 cm long, rachis of 7.5-16 cm long; numerous cincinnus, sessile. Flowers ca. 2 mm long, pedicel ca. 0.5 mm long; sepals 5, ca. 1 mm long, fused at the base, lobes ovate, acute, glabrous and with prominent veins on the internal surface, external surface villous; petals 5, ca. 1.5 mm long, obovate, obtuse, clawed, villous on the central part and margins, the rest glabrous; petal appendages rudimentary, bifid, smaller than the petals, basally adnate, villous; nectary disc glabrous, 5-lobed, lobes ca. 1 mm long; staminate flower: stamens 8, 1.5 mm long, filaments villous for more than half of their length, anthers glabrous, pistillode ca. 1.5 mm long; pistillate flower: staminodes ca. 1 mm long, pistil ca. 1.5 mm long, style 0.5 mm long, with 3 stigmas, ovary ca. 1 mm long. Fruits ovate, chartaceous, 5-5.5 × 2-2.3 cm; cocci slightly inflated, 1.2-1.4 × 1.1-1.4 cm, including the ca. 2-3 mm long stipe constricted at junction with wing; epicarp densely strigose (simple trichomes of same length) on cocci, strigose on wings; endocarp glabrous. Seeds trigonous ovoid, ca. 6 × 4 mm, basally attached, glabrous, mature embryo not observed.

Thinouia cazumbensis is differentiated from most species of Thinouia by the thyrses axillary, racemiform (Fig. 2A, C ) and the 5-lobed nectary disc, a character that is unique and for the first time recorded in the genus (Fig. 2E ). The lobed nectary disc within Thinouia should be further investigated through morpho-anatomical studies to understand how nectaries evolved within the genus.

Distribution and ecology.

Thinouia cazumbensis is known only from the Reserva Extrativista do Cazumbá-Iracema (Fig. 3 ) where it is an infrequent liana that reaches the canopy of the open rainforest with abundant bamboo ( Guadua spp.) ( Silveira 2005).

Phenology.

Collected in flower and fruit during July.

Etymology.

The epithet cazumbensis refers to Reserva Extrativista do Cazumbá-Iracema, where the species was collected. In the 1980s, local rubber tappers and extractivists fought against the area becoming a rural settlement and on 19 September 2002 succeeded in getting the area designated as a conservation unit ( ICMBio 2007). Situated in the State of Acre between the municipalities of Sena Madureira and Manoel Urbano, the Reserva Extrativista do Cazumbá-Iracema covers an area of 750,794.70 hectares of the Western Amazon Corridor, one of the seven major ecological corridors proposed for Brazil ( Ricardo and Lima 2004).

Conservation status.

The species is only known from one locality in Acre and is categorised as Data Deficient (DD) according to IUCN (2019). Further field studies are needed to evaluate its conservation status more accurately.

Figures

Figure 2. Thinouia cazumbensis A fruiting branch B detail of leaf, abaxial view C racemiform inflorescence with a pair of basal tendrils D detail of inflorescence (cincinnus) E flower with removed petals showing a 5 - lobed nectary disc F detail of fruit G infructescence (A-G) from H. Medeiros 3401 (RB). Photos by H. Medeiros.

Figure 3. Geographic distribution of Thinouia cazumbensis.