Dichorisandra fadenii Aona & M.C.E.Amaral, 2025

Aona, Lidyanne Yuriko Saleme, Souza, Everton Hilo De, Bittrich, Volker & Amaral, Maria Do Carmo Estanislau Do, 2025, Dichorisandra fadenii (Commelinaceae), a new villose species from southwestern Amazonia, Phytotaxa 682 (3), pp. 288-294 : 290-292

Dichorisandra fadenii Aona & M.C.E.Amaral , sp. nov. ( Fig. 2–3 )

Diagnosis: — Dichorisandra fadenii can be differentiated from other congeneric species by villose stem, sheaths, and both sides of the leaf blades, whitish flowers, six stamens, yellowish anthers, lanceoloid capsule with a long acuminate apex, and red-arillate seeds.

Type:— BRAZIL. ACRE. Manoel Urbano, Parque Estadual Chandless, 9˚23’47” S, 69˚56’52” W, Elev. 140 m, 05 April 2019 (fr), R. C. Forzza 10271, H. Medeiros , A. S. Lima , E. C. Oliveira , A. Contijo , M. Landeiro , F. A. Obermüller , M. Silveira & D. C. Daly (holotype RB!; isotype HURB!) .

Description: —Unbranched, 12‒30 cm, erect herbs. Roots not seen. Stem unbranched at the base, covered densely with rufus, villose hairs, internodes 4–11 cm long, distally shorter. Leaves alternate and distichous, sheaths 2‒2.2 cm long, distally shorter, becoming scarious, villose, with rufus trichomes, margin villose; petiole inconspicuous; blades elliptic to oblong, 13.7‒15 × 5‒7 cm, discolorous, sparsely villose on both sides, trichomes ca. 2 mm long, brownish, midvein conspicuous, margin ciliate, base oblique, apex acute to acuminate. Flowers in terminal, erect thyrse; cincinnus bract foliaceous, usually smaller than the leaves, 10‒11.5 × 2.2‒5 cm; peduncle 3‒3.5 cm long, densely pilose; cincinnus pedunculate, peduncle 3‒6 mm long, pilose, reduced distally, with 5‒10 cincinni compressed in 3–4-flowered, bracts linear, 5‒10 × 2‒3 mm, distally reduced, later scarious, persistent, porrect, abaxial glabrous, adaxial pilose, trichomes hyaline, ca. 2 mm long, margin sparsely ciliate, bracteoles deltoid, 2‒2.5 × 2‒2.5 mm, scarious, adaxial glabrous, abaxial pilose, margin sparsely ciliate; pedicels, 3‒5 mm long, pilose; buds ellipsoid, 6‒8 × 2‒3 mm, villose; flowers bisexual or male, 1‒1.5 cm diam., slightly zygomorphic; sepals 3, elliptic-lanceolate, 6‒8 × 3‒4 mm, greenish with hyaline margin, adaxial pilose; petals 3, elliptic to oblanceolate, 10‒11 × 3‒4 mm; stamens 6, slightly unequal, filaments erect, 5–6 mm long, yellowish, anthers oblong, 5‒5.5 mm long, faintly sagittate at base, yellowish, apical pores 2; ovary ca. 2 × 2 mm, globose, smooth, 3-celled; style 5–8 mm long, erect, apex curved; stigma capitate, trilobed; ovules 4–8 per cell. Capsule lanceoloid with acuminate apex, glabrous, 10‒12 × 6‒9 mm (in sicco). Seeds 2–4 per locule, pyramidal (in sicco), ca. 4 × 3 mm, arillate, aril reddish, testa black, slightly wrinkled.

Paratypes: — BRAZIL: Acre, Alto Juruá, Reserva Extrativista, localidade base ( Restauração ), Nov. 1993 (fr.), L.C. Berbacci 3210 (IAC) ; Marechal Taumaturgo, Rio Juruá, Reserva Extrativista do Alto Juruá , S of confluence with Rio Acuriá and N of São João do Breu, Colorado Tapaúna , 9˚051’S, 72˚41’W, ca. 200 m, 01 May 1993 (fl., fr.), D.C. Daly 7671 et al. (NY) ; Sena Madureira, Sena Madureira, Basin of Rio Purus , Rio Macauà , below Colônia Barro Alto , River descending 3 m below high water mark, 9°12’S, 68°44’W, 04 April 1994 (fr), D.C. Daly 8180 et al. (NY, US, UFACPZ). BOLÍVIA: Chochabamba, Carrasco, de Vila Tunari 62kms, hacia Puerto Vilarronel “Parque Litoral”, carca de Ivirgarzama, 400 m, 5-30˚W, 02 May 1979 (fr), G.Beck 1514 (US) ; Santa Cruz, Ichilo, Santa Cruz 130 kms, NW linea recta, puente rio Yapacani 35 ms, hacia Puerto Grether , 250m, 18 March 1981 (fl, fr), G.Beck 6607 (US). PERU: San Martin: Mariscal Cáceres, Dett. Tocache Nuevo, 08 Feb. 1970 (fl), J.Schuncke 3782 (F) ; Junin: Pixis Trail , 626 m, 28 Aug. 1929 (fr), E.P.Killip 26144 & A.C.Smith (F) .

Etymology:—The specific epithet honors Dr. Robert Bruce Faden (The United States National Herbarium), a great specialist of the taxonomy of Commelinaceae , who in 1981/1982 identified two collections of D. fadenii as belonging to an undescribed taxon.

Phenology:—Herbarium specimens indicate that this species was collected with fruits from March, April, May, August and November, and with flowers in March and May.

Distribution, habit and conservation status: — Dichorisandra fadenii is known from eight collection sites in three countries: Brazil (state of Acre: Manoel Urbano, Alto Juruá, Marechal Taumaturgo and Sena Madureira); Peru (San Martin and Junim), and Bolivia (Cochabamba and Santa Cruz) ( Fig. 2 ). In Acre, it is present in the Chandless State Park Conservation Unit and the Alto Juruá Extractive Reserve. The species occurs predominantly in riparian forests of forest remnants, occupying the understory of humid Amazon forests. The species was estimated to have an Extent of Occurrence (EOO) of 381.437,672 km 2 and an Area of Occupancy (AOO) of 20,000 km 2. The Amazon , which represents almost 50% of the remaining humid tropical forests, is one of the most important hotspots of natural resources and biological diversity on the planet ( Laurance et al. 2001, Costa et al. 2023). Based on the data on restricted occurrences in Amazonia and plausible threats, the suggested conservation status for Dichorisandra fadenii is Vulnerable (VU) B1a(iv)+2ab(i,ii). However, further precise data on its distribution and threats from all of its occurrences may can change the threat status in future.

The Amazon , home to about 40% of the world’s tropical forests and 10% of known species, is critical for global climate regulation ( Feng et al. 2021). However, deforestation, largely driven by agricultural fires, livestock expansion, mining, logging, and urban growth, threatens its biodiversity ( Costa 2020, Feng et al. 2021, Reis et al. 2021).

Brazil is home to most of the Amazon Rainforest. In the last five years (2019 to 2023) the Amazon lost an area of approximately 55.000 km 2, with a reduction of deforestation only in the last year (2023) with 22%. Deforestation in the state of Acre in this same period was 3,714 km 2. Acre was the Brazilian state in the Amazon that lost the largest forest area in relation to the size of its territory ( PRODES 2024). The main causes of forest loss are fires, deforestation to expand the area of livestock farming and the agricultural frontier in general, in addition to mining ( Feng et al. 2021, Reis et al. 2021, Oliveira Filho et al. 2022, Costa et al. 2023). Other direct drivers of forest loss include the opening of new roads, construction of hydroelectric dams, exploitation of minerals and oil, and urbanization ( Berenguer et al. 2021).

In Bolivia, the main causes of deforestation are fires, occurring mainly in protected areas with a high level of biodiversity, in addition to gold mining and land deforestation for agribusiness ( Costa 2020, Robbins 2024). The accelerated expansion of the agricultural frontier occurs mainly for the planting of soybeans and livestock farming, activities that are increasingly important in the country’s economy ( Costa 2020, Robbins 2024).

In Peru, agriculture is the main cause of deforestation in the Amazon . The planting of cocoa, coffee and coca are important historical causes of deforestation, especially in higher altitude areas ( Costa 2020, Rojas et al. 2021). Oil palm plantations represent a more recent driver of deforestation. Illegal gold mining is also an increasing threat to the Peruvian Amazon , especially on an artisanal scale ( Costa 2020, Rojas et al. 2021).

Although Dichorisandra fadenii has a relatively wide distribution from Brazil to Bolivia and Peru, this species occurs in areas that are strongly threatened by deforestation, as demonstrated above.

Notes: — Dichorisandra fadenii can be identified by its villose stems, sheaths, and leaves, whitish flowers, for presenting six stamens with yellow anthers opening by 2 apical pores and a capsule with a conspicuous acute rostrate apex – a unique character combination within the genus ( Fig. 2 ). Furthermore, the seeds have a notably reddish aril which appears to unite the seeds ( Fig. 2 ), however, in the study of the exsiccates, the presence of 2–4 separate arillate seeds was established.

The lanceoloid, long acuminate capsule ( Fig. 2 ) is characteristic to determine Dichorisandra fadenii in the field, which is unique in the genus as all other species possesses globose to terete fruits ( Aona 2008).

Dichorisandra bonitana and D. incurva ( Fig. 2B ) shares similarities with D. fadenii in white ( Fig. 3 ) petals (the former often recorded with lilac to purple petals). However, Dichorisandra bonitana ( Fig. 2C ) occurs in the tropical forest of Colombia ( Philipson 1956), and is known only by the type and protologue, and differs from D. fadenii by having branched habit, cream anthers and bluish pollen sacs, and terete, 3-ribbed, green, globose to broadly ellipsoid, apically rounded capsule. Whereas, D. incurva grows in semi-deciduous and deciduous forests exclusively in extra- Amazonian Brazil, in the states of Bahia, Espírito Santo, Rio de Janeiro, Minas Gerais, São Paulo, Paraná ( Aona 2008), and differs from D. fadenii by much branched habit, pendant apical branches, yellow anthers which distally opens introrsely short slits (functionally poricidal), terete, apically acute capsule ( Table 1).

Figures

FIGURE 2. Dichorisandra fadenii sp. nov. Photo: D.C. Daly (col. number Daly 7671 et al.). Note the lanceoloid capsule with long, acuminate apex, white flowers, and arillate seeds.

FIGURE 3. Images of the holotype of the names of the three species with white flowers and photos of the respective flowers except flowers of D. bonitana. A) Dichorisandra fadenii. B) Dichorisandra incurva. C) Dichorisandra bonitana.