Canavalia reflexiflora Snak, G.P. Lewis & L.P. Queiroz, 2015

Snak, Cristiane, Lewis, Gwilym Peter, Rocha, Douglas Eduardo & Queiroz, Luciano Paganucci De, 2015, A new species of Canavalia (Leguminosae, Papilionoideae) from Brazil with a specialized corolla suggesting bird pollination, Phytotaxa 207 (1), pp. 115-122 : 116-120

Canavalia reflexiflora Snak, G.P. Lewis & L.P. Queiroz , sp. nov. ( Figs. 2–5 )

It differs from other species of Canavalia by the combination of red flowers, wing and keel petals as long as the standard petal, standard reflexed and the oblong seed with a hilum surrounding nearly half the seed circumference.

Type:— Brazil. Minas Gerais: Caratinga, APA Pedra Itaúna, trilha do Silva, ca. 912 m elev., 19°48ʹ15.3ʹʹS 42°07ʹ19.9ʹʹW, 16 February 2014 (fl.), C. Snak, C. Silva & D. E. Rocha 1112 (holotype HUEFS, isotypes CESJ, K, RB).

Liana with glabrescent stems, terminal branches hirsute. Stipules deltoid, 2.7–3.75 mm long, caducous. Leaves pinnately trifoliolate; petiole 4–6.5 cm long, leaf rachis 1.5–3 cm long; leaflets 8–15 × 3.5–9 cm, ovate to widelyovate, apex acuminate to cuspidate, acumen 0.5–1 cm long terminating in a 1 mm long mucro, upper surface sericeous, lower surface sparsely sericeous, lateral leaflets asymmetric. Inflorescence an axillary, pendent, 30–65 cm long pseudoraceme; peduncle glabrescent; inflorescence nodes 1–5-flowered; pedicels 1.2–2.7 mm long; bracteoles deltoid, 0.8–1.5 mm long, caducous. Calyx red, 17–20 × 6.5–7 mm, glabrescent, bilabiate, tube 8–9.5 mm long, upper edge straight, upper lip with 2 larger lobes, 6.5–8 mm long, apex rounded, lower lip with 3 small teeth, so closely fused as to appear as one triangular–lanceolate tooth, 3–4 mm long; petals red, standard claw 3–4 mm long, an auricle on each side of the distal portion of the claw, lamina 2–2.5 × 1.4–1.6 cm, suborbicular, apex emarginate, a pair of callosities in the middle portion, trichomes sparse on both surfaces in the proximal region; wing petals 2–2.5 × 0.5 cm, claw 5–6 mm long, lamina oblanceolate, callosities present, not twisted, spur rounded, glabrous; keel petals 2–2.3 × 0.5 cm, claw 5–7 mm long, oblanceolate, not rostrate, spur acute; stamens 10, pseudomonadelphous, 22–25 mm long, anthers dorsifixed; ovary 10–13 mm long, pilose, stipe c. 3.5 mm long, style 7–9 mm long, stigma capitate. Legume 9–13 × 2–2.5 cm, slightly compressed laterally, spirally dehiscent, valves brown, each valve have a submarginal ridge running closely parallel to the upper suture. Seeds oblong, 12.9–14.8 × 7.5–8.5 × 4.2–5 mm, testa dark brown; hilum surrounding nearly half the seed circumference.

Distribution and habitat:— Canavalia reflexiflora is known only from two gatherings in the municipalities of Carangola and Caratinga, southeastern Minas Gerais, Brazil ( Fig. 3 ). It is recorded from semi-deciduous forest of the Mata Atlântica Domain, occurring in a very disturbed area (Carangola) or in an open and sunny area inside the forest (Caratinga).

Conservation status:— Canavalia reflexiflora is here assessed as Endangered (EN) according to the criteria B1 (extent of occurrence) and B2 (area of occupancy) of the IUCN Red List ( IUCN 2012). The area where this species was found in Caratinga is under enviromental protection, but is threatened by various human activities, especially coffee cultivation. The area in Carangola municipality is greatly disturbed and the species has not been recorded from there since 1988. We attempted to recollect it accompanied by the original collector but we were not successful. It is thus likely that the species is now extinct in that area.

Flowering and fruiting period:— Canavalia reflexiflora was collected with flowers in February and with fruits in July.

Systematic position:—According to the classification proposed by Sauer (1964), Canavalia is divided into four subgenera: Canavalia, Catodonia Sauer (1964: 116) , Maunaloa Sauer (1964: 174), and Wenderothia ( Schlechtendal 1838: 330–332) Sauer (1964: 123) . Canavalia reflexiflora belongs to subgenus Catodonia because the lower teeth of the calyx are borne on a jaw-like structure, the wing petals are not twisted, the two valves of the fruit each have a submarginal ridge running closely parallel to the upper suture, and the hilum surrounds approximately half the seed circumference. The new species is morphologically similar to Canavalia bonariensis Lindley (1828: 1199) , C. cassidea Lewis (1992: 305–307) , C. dolichothyrsa Lewis (1982: 123–125) , and C. parviflora , which also occur in eastern Brazil. The diagnostic morphological characters of these species are compared with those of Canavalia reflexiflora in Table 1. Red flowers are also found in C. bonariensis and C. cassidea , but they differ from the new species in their wing and keel petals being much smaller than the standard, while the new species possesses wing and keel petals approximately the same size as the standard. Canavalia reflexiflora also differs from C. bonariensis in having fruits with a spiral dehiscence and oblong seeds (versus fruits with an irregular dehiscence and seeds almost circular in C. bonariensis ). Canavalia dolichothyrsa and C. parviflora also have fruits with spiral dehiscence and oblong seeds, but differ from the new species by their pink flowers. Canavalia parviflora also differs from C. reflexiflora in the relatively smaller size of its wing and keel petals. Canavalia dolichothyrsa differs from the new species in its 90–100 cm long inflorescences (vs. 30–65 cm long in C. reflexiflora ), fruits ca. 22 cm long (vs. 9–13 cm long), and hilum surrounding ca. ⅓ of the seed circumference (vs. ½ of the seed circumference).

Etymology:—The specific epithet of the new species derives from the Latin reflexus (curved backwards or downwards) and flos (flower), the two combined to describe the backwardly curved standard petal in the flower ( Fig. 3D ).

Pollination:—The flowers of Canavalia reflexiflora differ from the general pattern observed in the genus which, where known, are pollinated by bees. In Canavalia reflexiflora the flowers are red, floral scent is imperceptible, the wing and the keel petals are elongated into a tube, and the standard is strongly reflexed backwards over the calyx ( Figure 3D ). Thus, the wing and keel petals together function as a tubular flower while the reflexed position of the standard does not provide a landing platform for bees but makes the flower ideally adapted for hovering longbeaked hummingbirds. Our field observations in Caratinga recorded several hummingbirds visiting the flowers of C. reflexiflora . One of the most commonly sighted species was the reddish hermit ( Phaethornis ruber Linnaeus ) which clearly contacted the reproductive organs of the flower while foraging for nectar. ( Fig. 5 ).

Hummingbird species previously have been observed visiting the flowers of Canavalia brasiliensis and C. parviflora ( Guedes et al. 2009, Franco 1995, respectively). The species Phaethornis ruber , Chlorostilbon aureoventris D’Orbigny & Lafresnaye and Eupetomena macroura Gmelin were recorded visiting C. brasiliensis , although these species extracted nectar without touching the reproductive organs ( Guedes et al. 2009). Nevertheless, Franco (1995) studied C. parviflora and observed the flowers being visited by the hummingbird Amazilia lactea Lesson which touched the reproductive organs and was considered to be a secondary pollinator.

The visits by hummingbirds recorded for Canavalia brasiliensis and C. parviflora were infrequent compared to the large number of visits made by bees, which are considered to be the primary pollinators of the species ( Franco 1995, Guedes et al. 2009). Furthermore, the flowers of these species have the typical morphology for pollination by large bees, with the standard petal acting as a landing platform and provided with nectar guides and a distinct scent.

We consider the unique flower morphology of Canavalia reflexiflora , which markedly contrasts with the general pattern for the genus, to be strong evidence of hummingbirds as the primary pollinator of the species.

Additional specimens examined (paratypes):— BRAZIL. Minas Gerais: Carangola, Fazenda São Sebastião , ca. 700 m elev., February 1988 (fl.), L. S. Leoni 154 ( CESJ, GFJP, K) ; Caratinga, APA Pedra Itaúna , ca. 895 m elev., 19°48ʹ11.7ʹʹS 42°07ʹ24.6ʹʹW, 29 July 2014 (fr.), D. E. Rocha s.n. ( HUEFS 212747 ) .

Figures

FIGURE 2. Canavalia reflexiflora. A. Habit. B. Leaflet indumentum. C. Branch and part of a peduncle. D. Inflorescence. E. Floral bud. F. Flower. G. Calyx. H. Standard. I. Wing petals. J. Keel petals. K.Androecium. L. Gynoecium (Drawn from C. Snak et al. 1112). DRAWN BY ROSANE QUINTELLA.

FIGURE 3. Canavalia reflexiflora. A. Habit. B. Leaves. C. Inflorescence. D. Flower with the reflexed standard (arrow). E. Immature fruits. F. Mature fruits. G. Seeds.

FIGURE 4. Distribution of Canavalia reflexiflora (BA = Bahia; ES = Espírito Santo; GO = Goiás; MG = Minas Gerais; RJ = Rio de Janeiro; SP = São Paulo).

FIGURE 5. Phaethornis ruber visiting Canavalia reflexiflora in Caratinga, Minas Gerais, Brazil.