Begonia imbrexiformis Moonlight, 2023

Moonlight, Peter. W., Jara-Muñoz, Orlando A., Purvis, David A., Delves, Jay, Allen, Josh P. & Reynel, Carlos, 2023, The genus Begonia (Begoniaceae) in Peru, European Journal of Taxonomy 881, pp. 1-334 : 81-84

12. Begonia imbrexiformis Moonlight sp. nov.

urn:lsid:ipni.org:names:77323288-1

Figs 24A , 29

Diagnosis

Most similar to B. obtecticaulis but differs in its straight, elliptic leaves that are cuneate at the base (vs lanceolate to ovate leaves with an obliquely cordate base) and have pinnate (vs palmate-pinnate) venation. It further differs in its denticulate (vs irregularly double-dentate) leaf margins; its stipules, which are in uneven pairs and have an asymmetrical base, with the larger side auriculate (vs with a symmetrical base, both sides cuneate); its smaller tepals on the staminate flowers (5–11 × 5–10 mm vs 12–14 × 12–15 mm); and its more numerous stamens (ca 35 vs 25–30).

Etymology

The species’ epithet derives from the Latin noun ‘ imbrex ’, which refers to a semi-cylindrical roofing tile. This derives from the species’ long, red-brown stipules, which clasp the stem and overlap each other up the length of stem. These are reminiscent of the roofing tiles which give the city of Cuzco its distinctive terracotta colour.

Type

PERU – Cusco Region: Prov. Calca • Dist. Yanatile, camino hacia Lacco Yavero ; 12°15′ S, 72°18′ W; 1567 m a.s.l.; 27 Feb. 2005; L. Valenzuela, E. Suclli & J. Farfán 5315; holotype: MO [ MO-1838287 ] .

Description

Caulescent herb, to 0.3 m high. Stem erect, rarely branching; internodes to 6 cm long, to 4 mm thick, succulent, red, glabrous. Stipules in unequal pairs, persistent, lanceolate, clasping the stem, 11–35 × 4–10 mm, apex obtuse, base asymmetrical, auriculate on the broad side, cuneate on the narrow side, translucent, pale brown, glabrous, margin entire, aciliate. Leaves> 5 per stem, alternate, basifixed; petiole 0.8–1.4 cm long, red, glabrous; blade asymmetric, elliptic, to 6.5 × 2.2 cm, succulent, apex acuminate, base obliquely cuneate, rarely truncate on the larger side of the lamina, margin denticulate, ciliate, upper surface green, glabrous, lower surface pale grey-green, glabrous, veins pinnate, with 6–8 secondary veins on the larger side, 4–7 secondary veins on the smaller side. Inflorescences 1–3 per stem, bisexual, axillary, erect, cymose, with 2 branches, bearing up to 4 staminate flowers and 4 pistillate flowers, protandrous; peduncle to 3 cm long, red, glabrous, bracts deciduous, lanceolate to ovate, 3–5 × 1–3 mm, translucent, colour unknown, glabrous, apex rounded to truncate, margin entire to irregularly serrate, aciliate. Staminate flowers: pedicels to 12 mm long, glabrous; tepals 2, spreading, broadly ovate, 5–11 × 5–10 mm, apex obtuse, pink, glabrous, margin entire, aciliate; stamens ca 35, spreading, yellow, filaments 1–2.5 mm long, free, anthers ellipsoid, 1.2–1.5 × 0.5 mm, dehiscing via lateral slits, connectives extending to 0.4 mm, symmetrically basifixed. Pistillate flowers: pedicels to 8 mm long; bracteoles 2, positioned directly beneath the ovary, lanceolate, ca 2 × 0.5 mm, apex acute, margin entire, translucent, glabrous, colour unknown; tepals unknown; ovary body narrowly ovoid, 4–7 × 2 mm, colour unknown, glabrous, unequally 3-winged, wings triangular, largest ca 8 × 8 mm, smallest 6–7 × 2–3 mm; 3-locular, placentae branches divided, bearing ovules on both surfaces; styles 3, yellow, free, ca 3 mm long, irregularly 2–5 times-divided, stigmatic papillae in a spirally twisted band. Fruiting pedicel to 14 mm long. Fruit body ovoid, to 11 × 6 mm, drying brown, wings same shape as in ovary, the largest expanding to 12 × 12 mm, the smallest expanding to 11 × 3 mm.

Proposed conservation assessment

Known from a single specimen in a poorly explored part of the Santuario Nacional de Megantoni protected area in Cusco Region, Peru. No information is known about the species’ population size or trends in its population. We assess B. imbrexiformis sp. nov. as Vulnerable (VU D2).

Notes

The large, clasping stipules of B. imbrexiformis sp. nov. are very unusual within Begonia . They are shared with B. obtecticaulis , which is likely closely related, and similar to those found in B. venosa Skan ex Hook. f. and B. curtii L.B.Sm. & B.G.Schub. , which are distantly related members of B. sect. Pritzelia found in the Mata Atlantica of southeast Brazil. All three of these species live in relatively seasonal habitats. For example, B. obtecticaulis , lives in small patches of montane forest surrounded by grassland. The clasping stipules may be adapted to prevent water loss during dry periods. The stipules of the newly described species are however unique both in coming in unequal pairs and in having an asymmetrical base. We know of no other cases of unequal, asymmetrical stipules in South American Begonia , but this is found in Asian Begonia such as B. hughesii R.Rubite & C.-I Peng ( Rubite et al. 2015).

The sectional placement of B. imbrexiformis sp. nov. is unclear and it falls between the current circumscriptions of B. sects. Cyathocnemis , Hydristyles, and Ruizopavonia. These sections were considered similar by Doorenbos et al. (1998) and their circumscriptions remained largely unchanged in the latest community-led revision of the sections of Begonia ( Moonlight et al. 2018) Few species of these three sections have been included in molecular phylogenies and southern Andean species have been particularly poorly represented. The current circumscriptions are unlikely to survive intensive study by molecular phylogenetics. In most respects, B. imbrexiformis sp. nov. best resembles B. sect. Cyathocnemis but its pinnate venation is reminiscent of B. sect. Ruizopavonia while its multifid styles are more common in B. sect. Hydristyles. We tentatively place B. imbrexiformis sp. nov. in B. sect. Cyathocnemis and this placement is supported by its similarity to B. obtecticaulis , which was placed in B. sect. Cyathocnemis by molecular data ( Moonlight et al. 2018).

Identification notes

Other than B. obtecticaulis (see Diagnosis) it is unlikely that B. imbrexiformis sp. nov. will be confused with any other species of Peruvian Begonia . Its straight, pinnately nerved leaves are relatively uncommon among Peruvian begonias and are unique in combination with its large, persistent stipules that overlap each other up the length of the stem.

Distribution and ecology

Endemic to Peru and Cusco Region ( Fig. 24A ). Found in middle montane forest at an elevation of 1567–2040 m a.s.l. Begonia imbrexiformis sp. nov. may be most common on the edge of montane forest patches in common with most of its relatives.

Figures

Fig. 24. Distribution ofBegonia sect.Cyathocnemis (Klotzsch)A.DC. in Peru and surrounding countries. A. B. amoeboides Moonlight (red) andB. imbrexiformis Moonlight sp. nov. (blue).B. B. bracteosaA.DC. (red) and B. longinqua Moonlight (blue). C. B. cyathophora Poepp. & Endl. (red), B. serratistipula Moonlight sp. nov. (blue) and C. vargasii Moonlight sp. nov. (green). D. B. lamolina Moonlight (red), B. lophoptera Rolfe (blue) and B. obtecticaulis Irmsch. (green). Black lines indicate country borders, grey lines indicate major administrative divisions, blue lines indicate rivers, and shading indicates elevation.

Fig. 29. Begonia imbrexiformis Moonlight sp. nov. A. Habit. B. Unequal pair of stipules. C. Leaf, abaxial surface. D. Close up of leaf margin. E. Staminate flower, front view. F. Gynoecium, side view. G. Stamen, front and side view. H. Fruit, side view. I. Bract. Illustration by Claire Banks from L. Valenzuela, E. Suclli & J. Farfán 5313 (MO).