Rinorea stevensii Hoyos-Gómez, 2024

Hoyos-Gómez, Saúl E., Callejas Posada, Ricardo & Wahlert, Gregory A., 2024, Seven new species of Rinorea (Violaceae) from the Neotropics, PhytoKeys 242, pp. 241-271 : 241-271

4. Rinorea stevensii Hoyos-Gómez sp. nov.

Type.

Colombia. Dept. Vichada: Parque Nacional “ El Tuparro , ” piedra canal near the south end of airstrip at Centro Administrativo , 5 ° 17 ' N, 67 ° 52 ' W, ca. 100 m elev., 5 Mar 1985, J. L. Zarucchi et al. 3577 (holotype: NY [barcode 04205808 ]!; isotypes: COAH [cat. 24597 ]!, COAH [cat. 55474 ]!, FMB [cat. 4307 ]!, FMB [cat. 21506 ]!, MO [acc. 3499269 ; barcode MO- 1592746 ]!, U [barcode U 1766360 ]!) .

Description.

Rinorea stevensii is similar to R. ovalifolia by the lamina base symmetrical, style erect and two glabrous seeds per valve, but it differs by the lamina abaxial surface with golden pubescence (vs. the lamina abaxial surface glabrescent in R. ovalifolia ), domatia present (vs. domatia absent), inflorescences cylindrical, 2–5 cm long (vs. inflorescence conical, 4–12 cm long), costa of petals and sepals pubescent (vs. costa of petals and sepals glabrescent), filaments free (vs. filaments fused), and capsule pubescent (vs. capsule glabrescent).

Trees 1.5–4 m tall, terminal branchlets pubescent with erect golden trichomes 0.4–0.5 mm long. Leaves opposite, petiolate; petiole 2–6 mm, pubescent with long golden trichomes 0.3–0.4 mm long; stipules deciduous, free, lanceolate, herbaceous, 2.5–5 × 1–1.5 mm, pubescent with appressed golden trichomes 0.4–0.5 mm long; margin entire; lamina elliptic, 4–12.5 × 2.5–7 cm, adaxially pubescent on mid-vein and abaxially pubescent on mid-vein and secondary veins with erect golden trichomes 0.4–0.5 mm long; semi-craspedodromous, with 6–9 major secondary vein pairs, secondary veins with irregular spacing and vein angles smoothly decreasing proximally between them, base rounded, symmetrical, margin crenate, ciliate, apex acuminate, acumen 0.5–1 cm long, mucronate, domatia present. Inflorescence axillary, lateral or terminal, racemose, 2–5 cm long, 1–1.5 cm diam., axis pubescent with erect golden trichomes 0.4–0.5 mm long; pedicels 2.5–6.5 mm, pubescent with erect golden trichomes 0.4–0.5 mm long, articulated near the middle; bractlets persistent below articulation, subopposite, ca. 1 × 1 mm, herbaceous, costa pubescent with appressed golden trichomes 0.4–0.5 mm long; peduncle bracts persisting, broadly triangular, 1–1.5 × 1–1.5 mm, herbaceous, pubescent with appressed golden trichomes 0.4–0.5 mm long, margin ciliolate. Flowers 2.8–3.8 × 3–3.4 mm long, sepals subequal, triangular, 2–2.5 × 1–1.6 mm, 7–11 - veined, pubescent with appressed golden trichomes 0.5 mm long, margin ciliolate; petals lanceolate, 2.8–4.3 × 1.2–1.9 mm, costa pubescent with appressed golden trichomes 0.3–0.4 mm long, margin entire, cream to yellow in vivo, pale brown when dry; stamens 2.5–3 mm long, all filaments free, 0.4–0.6 mm, dorsal gland covering completely the filament, glabrous; anthers elliptic, 1.4–1.7 × 0.3–0.8 mm, apex obtuse, connective 0.8–0.9 mm, dorsal connective scale lanceolate, 2.4–2.5 × 0.9–1.0 mm long, margin subentire, scarious, orange-brown; ovary globose, 0.8–1.5 × 0.7–1.3 mm, pubescent with appressed golden trichomes 0.5 mm long; style erect, filiform, 1.8–2.4 × ca. 0.1 mm long, pubescent proximally with appressed trichomes 0.5 mm long, stigma acute. Fruit a symmetrical, subligneous capsule dehiscent along three sutures, ellipsoid, 1.5–2.3 × 0.5–0.6 cm, acuminate at the apex, veined, pubescent with erect golden trichomes 0.5 mm long, green when fresh, brown when dry. Seeds two per valve, globose, 4–5 mm diam., glabrous, without maculae, brown when dry. (Fig. 7 )

Distribution and habitat.

Rinorea stevensii occurs in Colombia in the border region with Venezuela near the Orinoco River and in El Tuparro National Park. It also occurs in Venezuela in the vicinity of Puerto Ayacucho. This distribution corresponds to the Biogeographical Provinces of Pantepui and Sabana, in the Boreal Brazilian and Pacific Dominions, respectively (sensu Morrone (2014)). The species grows on granitic hills and slopes in lowland semi-deciduous tropical rainforests and savannahs, at elevations of 85– 520 m. (Fig. 6 )

Etymology.

Rinorea stevensii is named in honour of Dr. Peter Stevens, Professor of Biology at the University of Missouri Saint-Louis and curator of the Missouri Botanical Garden. Prof. Stevens was the major advisor for SEHG’s master’s degree.

Vernacular names.

Aruni yó (B. M. Boom et al. 6564).

Conservation status.

Rinorea stevensii has a geographic range in the form of an EOO of 5,070 km 2 and AOO of 56 km 2. It is represented by two locations within the El Tuparro National Park in Colombia and eight locations outside of protected areas in Venezuela where it is threatened by deforestation, illegal resource extraction and uncontrolled fires. Based on its limited AOO, the number of locations and the projected continuing decline in the quality of habitat, the species is preliminarily assigned to the “ Vulnerable ” category [ VU B 2 ab (iii)].

Notes.

Based on several morphological differences and an allopatric distribution, Rinorea stevensii is segregated from R. ovalifolia (as circumscribed by Hekking (1988)). Hekking noted the variable morphology of some specimens now representing R. stevensii , but he was unsure of their placement: “ The leaves of Rinorea ovalifolia are variable in character, e. g. the underside of the leaves varies from densely hispidulous to glabrescent and domatia may be present or not ”. Hekking invoked introgressive hybridisation between R. ovalifolia and R. pubiflora var. pubiflora to explain the morphological variability, but we disagree with his opinion. We hypothesise that the distinctive morphological characteristics and the discrete biogeographic distribution suggest that R. stevensii is a separately evolving lineage (sensu De Queiroz (2007 )) making it worthy of recognition at the rank of species. Key morphological differences amongst R. stevensii , R. ovalifolia and R. pubiflora var. pubiflora are presented in Table 1 .

In addition to an allopatric distribution, Rinorea stevensii can be differentiated from R. chiribiquetensis (the other species segregated from R. ovalifolia ) by several morphological characters. It has longer and more abundant pubescence on the lamina, with trichomes 0.4–0.5 mm long (vs. shorter and less abundant pubescence on the lamina, with trichomes 0.2–0.3 mm long in R. chiribiquetensis ), larger lamina, 4–12.5 × 2.5–7 cm (vs. smaller lamina, 3.2–4.2 × 1.6–3.6 cm) and larger petals 2.8–4.3 × 1.2–1.9 mm (vs. 3–3.3 × 1.4–1.6 mm). Rinorea pubiflora var. pubiflora co-occurs with R. stevensii , but it is differentiated by having three pubescent seeds per valve, whereas R. stevensii has two glabrous seeds per valve.

Additional specimens examined.

Colombia. Dept. Vichada. Mpio. de Puerto Carreño: Cerro al N del Centro Adm. Inderena , 5 ° 21 ' 17.0 " N, 67 ° 51 ' 40.6 " W, 4 Apr 1995 (fr), M. P. Córdoba et al. 1266 ( COAH, COL, FMB) ; base del cerro Rocoso , 100 m elev., 8 Oct 1979 (fl), P. Vincelli 1047 ( COAH, COL, FMB) . Venezuela. Estado Amazonas. Mpio. De Puerto Ayacucho: 35 km. south of Puerto Ayacucho , at the “ Tobagón ”. Large igneous outcrop bordering forest on slope, 85 m elev., 4 May 1977 (fr), J. Steyermark & O. Huber 113844 ( COL, MO) . Mpio. de Atures: 23 km NE of Puerto Ayacucho and 10 km E of the highway, hills and base of hills, near Cachama , 90 m elev., 5 ° 51 ' N, 67 ° 24 ' W, 90 m elev., 19 Apr 1978 (fr), G. Davidse et al. 15300 ( MO, NY, U, US) ; 14–15 km NE of Puerto Ayacucho , along road to “ El Burro , ” 5 ° 47 ' N, 67 ° 32 ' W, 85 m elev., 15 Apr 1978 (fr), G. Davidse et al. 15070 ( MO, NY, US) ; alrededores de Puerto Ayacucho + / - 11 km N, 5 ° 44 ' N, 67 ° 30 ' W, 15 Apr 1978 (fl), O. Huber et al. 1450 ( U, US) ; ibid., 5 ° 43 ' N, 67 ° 30 ' W, 29 Jan 1978 (fl), O. Huber et al. 1502 ( K, NY, U, US) ; Piedra el Berraco, laja granítica que conduce a Provincial , 10 km al NE de Puerto Ayacucho , 5 ° 47 ' N, 67 ° 34 ' W, Apr 1997 (fl, fr), Á. Fernández-Pérez et al. 10800 ( US) ; E of río Parguaza, 125 km N of Puerto Ayacucho , 6 ° 17 ' N, 67 ° 5 ' W, 11 Sep 1985 (st), J. A. Steyermark et al. 131751 ( MO, U) ; Parguaza , 22 Apr 1946 (fr), I. Velez 2448 ( US) . Estado Bolivar. Mpio. Cedeño: vicinity of Panare village of Corozal , 6 km from Manipure towards Caicara , 6 ° 55 ' N, 66 ° 30 ' W, 24 Sep 1985 (st), B. M. Boom et al. 6083 ( NY) ; ibid., 6 ° 55 ' N, 66 ° 30 ' W, 90 m elev., 19 Apr 1986 (fr), B. M. Boom & M. Grillo 6564 ( MO, F, U, US) ; carretera Caicara – El Burro , 16 Apr 1984 (fl), B. Stergios et al. 8494 ( MO) ; Caicara 100 m elev., 10 Jun 1940 (st), L. W. Williams 13255 ( F) . Mpio. Foráneo La Urbana: cerca a la desembocadura del río Orinoco , 6 ° 46 ' N, 67 ° 00 ' W, 31 Jan 1989 (fl), N. Cuello 718 ( MO, U, US) ; Los Pijiguaos, afloramiento granítico 1.5 km al N del campamento Bauxiven , 6 ° 35 ' N, 66 ° 47 ' W, 7 Aug 1993 (st), A. Gröger et al. 1077 - B ( MO) ; E slopes of cerro Pijiguao ( N end of serrania Suapure ) above Pijiguao, ca. 70 km from mouth of Río Suapure , 110–520 m eelv., 19 Jan 1956 (fl), J. J. Wurdack et al. 41295 ( F, K, MG, MO, NY, U, US) .

Figures

Figure 6. Distribution of Rinorea chiribiquetensis (circle), R. ovalifolia (triangles), R. stevensii (stars).

Figure 7. Rinorea stevensii Hoyos-Gómez A habit B detail of young twig showing lenticels and pubescence C detail of leaf showing domatia, abaxial surface D detail of leaf showing margin ciliate, adaxial surface E branchlet with inflorescences F leaf architecture G infructescence H flower I sepals, abaxial surface J petals, abaxial surface K stamens, showing adaxial and abaxial surfaces L gynoecium M fruit N detail of fruit showing two seeds per valve O seed. (A – D: B. M. Boom 6564 [MO]; E – O: J. L. Zarucchi 3577 [MO]).