Gonolobus rumihuilcanus A.Cerchiai & L.O.Alvarado, 2022

Alvarado-Cárdenas, L. O. & Cerchiai, Alicia, 2022, A new species of Gonolobus (Apocynaceae, Asclepiadoideae, Gonolobineae) from Loja, Ecuador, Phytotaxa 575 (3), pp. 287-293 : 288-291

Gonolobus rumihuilcanus A.Cerchiai & L.O.Alvarado sp. nov.

— Type: Ecuador, Prov. Loja. Vilcabamba , Bosque y Vegetación Protectores Rumi Wilco , 1500 m., 17 December 2020 (fl.), A. E. Cerchiai M. 12 (holotype LOJA!, isotype HUTPL!) .

Gonolobus rumihuilcanus is morphologically similar to G. leianthus because of their green corollas, white and conspicuous faucal corona, and corolla lobes with margins albo-papillose. The new species differs by having a homogeneous distribution of pubescence on the stem (vs. trichomes distributed in two rows, in G. leianthus ), its sepals ovate-lanceolate to elliptic-lanceolate, 1–1.4 × 0.3–0.5 cm (vs. widely ovate, 0.8–1.9 × 0.6–1.1 cm, in G. leianthus ) G. rumihuilcanus is restricted -within the Loja province- to Vilcabamba, Ecuador, growing above 1500 m a.s.l. (vs. distributed from Mexico to Nicaragua, from 600 to 1400 m a.s.l G. leianthus ).

Herbaceous perennial vines. Latex white. Stems with mixed indumentum, occurring all around the stem, dense in young branches, glandular-capitate trichomes, 0.02–0.05 mm long, spreading, eglandular trichomes hirsute, short eglandular trichomes 0.03–0.05 mm long, eglandular trichomes 0.7–1.3 (1.5) mm long, both sparsely to densely placed, white to translucent, septate, erect. Leaf blades ovate to oblong-ovate, 8–18.3 × 3.5–8.7 (–10) cm, base cordate, basal lobes 1.0– 2.5 cm long, sometimes convergent, apex acute to rounded, abruptly acuminate, acumen narrowly obtuse, 5–9 mm long, adaxial surface with short eglandular trichomes 0.03–0.05 mm long, eglandular trichomes 0.7–1.1 mm long, both sparsely placed, densely in the midvein, white to translucent, erect to adpressed, abaxial surface sometimes with glandular-capitate trichomes, short eglandular trichomes 0.03–0.05 mm long, eglandular trichomes 0.7–1.1 mm long, both sparsely placed, densely in the midvein, white to translucent, erect to adpressed, margins entire, colleters 2–4, 0.5–0.8 mm tall; petioles 3.5–6 cm long, mixed indumentum, distributed all around, glandular-capitate trichomes 0.02– 0.75 mm long, spreading, short eglandular trichomes 0.02–0.03 mm long, eglandular trichomes 0.6–1.5 mm long, both sparsely to densely placed, white to translucent, erect; stipular colleters 0–2. Inflorescences racemiform, peduncles 2.5–3.5 cm long, indumentum as on the petioles or more scarce; pedicels 5.0– 6.8 cm long, indumentum as on the petioles, bracts linear to linear-lanceolate, 0.3–0.8 × 2–8.5 mm, caducous, adaxially glabrous and abaxially scattered pubescent. Calyx lobes 5, ovate-lanceolate to elliptic-lanceolate, 1–1.4 × 0.3–0.5 cm, patent to reflexed, apex acute, reddish brown, margins glabrous, adaxial surface glabrous, abaxial surface with mixed indument basally; colleters 2–5 per sinus. Corolla 4.8–6 cm diam., rotate, green faintly reticulated, tube 5–6 mm long, campanulate, lobes 5, oblong, 2–3.0 × 1–1.5 cm, slightly overlapping at the base, apex abruptly acuminate, adaxial surface papillose-pubescent diagonally distributed, trichomes to 0.12 mm, right margin with a white line, densely papillose-glandular, papillae 0.08–0.12 mm, abaxial surface glabrous; faucal annulus (corolline corona), 5-lobed, ca. 1.0 mm wide, white, shorthispid distributed all around the annulus, eglandular trichomes 0.5–0.8 mm long; gynostegial corona of fused staminal and interstaminal parts, 5-lobed, erect-striate, margin crenate, yellow; anther with laminar dorsal anther appendages 2.5 × 2.3–2.5 mm, square, adaxially concave, yellow, margin red; style-head 4.5–5 mm diameter, deeply angulate (starshaped), apex reddish, orange or yellow, concave, stipe ca. 3.0 mm. Pollinarium: corpusculum elliptic, 0.2–0.3 mm long, pollinia borne horizontally, oblong-ovate ca. 1.1 × 0.4 mm. Follicles ovoid, ca. 15.8–17 × 6.1 cm, base recurved, apex acute, 5-winged, wings 1–1.3 cm tall, margin entire to slightly crenulated, glabrous. Seeds 6–6.5 mm × 3–3.2 mm, obovate, glabrous, margin 0.8–1.3 mm wide, chalazal zone denticulate, coma 2.0 cm long, white. Figures 1–3 .

Distribution and Habitat:— Gonolobus rumihuilcanus is endemic to the province of Loja, in tropical subcaducifolious forest, dry scrub and forest with cacti along ravines and perturbed areas derived thereof, growing from 1500 to 2000 m a.s.l.

Phenology & ecology: —Flowering between September and January. Fruiting in March–June ( Figure 1 ). The flowers of this species are visited by different insects. Ants, Formicidae , and individuals of different fly families, such as Drosophilidae ( Figure 2A ), Sarcophagidae ( Fig. 2B ), and Tachinidae ( Fig. 2C ), were observed approaching the secretory zones of the flower. None of the visitors were observed to remove the pollinaria from the flower. However, it is likely that flies are the potential pollinators, as has been observed in several members of Gonolobus and Gonolobinae ( Ollerton et al. 2018).

Etymology:— The name refers to the protected vegetation zone Rumi Wilco, where the holotype of the species was collected. In Quichua, “Rumi” is intended to mean Stone and “Wilco” or “Huilco” is the name of the sacred tree for the Incas, Anadenanthera colubrina (Vellozo 11: t. 16) Brenan (1955: 182), Fabaceae , with numerous cultural, economic, and medicinal uses ( Torres & Repke 1996, de Viana et al. 2014).

Conservation Status:— Endangered (En, B2abii, iii) ( IUCN 2019). This species appears restricted to a very small zone of the Loja province, Ecuador (EOO= 32.135 km 2; AOO= 12 km 2). Specimens have been collected in only two localities. In the valley of Vilcabamba, within the Rumi Wilco tropical semideciduous protected forest (our collections). The other locality is under anthropogenic impact and affected by a reduction in both the extent of occurrence and habitat quality.

Additional specimens examined:— Ecuador, Prov. Loja . Vilcabamba, Bosque y Vegetación Protectores Rumi Wilco, 1500 m, 28 November 2020 (fl.), colector: A. E. Cerchiai M. 11 ( HUTPL) . Road La Toma-Loja , km 12, 2000 m, 2 September 1988, J. E. Mandsen & L. Ellemann 75179 (LOJA) .

Notes:— This discovery is remarkable for Ecuador because the last Gonolobus described for the country was 28 years ago ( Morillo 1994). With this new addition, five species are present in the country, three of which are endemic ( Gonolobus campii Morillo (47: 353), G. rumihuilcanus , G. saraguranus Morillo , Fig. 3 ).

Gonolobus rumihuilcanus is most similar to G. leianthus ( Fig. 3E–F ). They both have showy green flowers, corolla lobes oblong, with an obvious white margin and a white and pubescent faucal ring ( Fig. 1 , 3A ). The new species is distinguished by having a homogeneous distribution of pubescence on the stem (vs. trichomes distributed in two rows, in G. leianthus ); sepals ovate-lanceolate to elliptic-lanceolate, 1–1.2 × 0.3–0.4 cm (vs. widely ovate, 0.8–1.9 × 0.6–1.1 cm, in G. leianthus ). Gonolobus rumihuilcanus is found in Vilcabamba, Loja province, Ecuador, growing from 1500 m a.s.l. (vs. distributed from Mexico to Nicaragua, from 600 to 1400 m a.s.l for G. leianthus ) ( Stevens 2009).

Other taxa that showed morphological similarity are G. albomarginatus , and G. saraguranus . Gonolobus albomarginatus , also from Ecuador, has pedicels (3.0– 5.2 cm long), sepals (0.8–1.0(–1.4) cm long), and corolla lobes (1.8–2.5 cm long) of similar size when compared with G. rumihuilcanus , but the former differs by trichomes distribution on the stem (in two rows, vs. homogeneously distributed in G. rumihuilcanus ), corolla lobes shape (lanceolate vs. oblong in G. rumihuilcanus ), and the corolla lobes abaxial pubescence (glandular pubescent ( Stevens 2009), vs. glabrous in G. rumihuilcanus , Fig. 1C ). Both G. rumihuilcanus and G. saraguranus are found in Loja province, have broadly rotate green corollas with lobe margins albo-papilose. Gonolobus rumihuilcanus differs by its sepal length (1–1.2 cm vs. 5.5–6.2 mm in G. saraguranus ), corolla size (4.8–6 cm diam. vs. 2.8–3.1 cm in G. saraguranus ), corolla lobe shape and abaxial pubescence (oblong, glabrous vs. narrowly ovate, puberulous with short erect hairs in G. saraguranus, ( Morillo 1994) , Fig. 3I ).

Figures

FIGURE 1. Gonolobus rumihuilcanus. A. Branch with leaves and flowers. B. Young stem densely pubescent. C. Old stem with sparse pubescence. D. Colleters in the base of the leaf. E. Floral button and patent sepals. F. Abaxial view of the flower, showed the calyx and pedicel. G. Frontal view of the flower. H. Close-up of the gynostegium. I. Close-up of the corolla lobe, showing the marginal pubescence and glandular white line. J. Longitudinal section of the flower. K. Ripped fruit. Abbreviations: AA: Antheral appendage, CC: Coroline corona, GC: Gynostegial corona, Po: Polinaria. Photos: Alicia Cerchiai. Based on A. E. Cerchiai M. 12 (holotype LOJA)

FIGURE 2. Visitors observed on the flowers of Gonolobus rumihuilcanus. Flies of the families Drosophilidae (A), Sarcophagidae (B) and Tachinidae (C). Photos: Alicia Cerchiai.

FIGURE 3. Comparison of members of Gonolobus. A–B. Gonolobus rumihuilcanus (B. Type: A. Cerchiai 12, LOJA) C–D. Gonolobus albomarginatus (D. J. Folsom 9953, MO). E–F. Gonolobus leianthus (F. G. Aguilar 2959, MEXU). G–H. Gonolobus ophioglossa (H. R.L. Dressler 3823, MO). I. Gonolobus saraguranus (Type: L. Ellemann 66832, LOJA). Credit of the photos:A–B:A. Cerchiai, C: B. Hammel (http://legacy.tropicos.org/Image/58463), E: Hermes Vega (https://www.naturalista.mx/observations/29344234), G: Jan Meerman (https:// www.naturalista.mx/observations/29492107).