Handroanthus grandiflorus Espírito-Santo & M.M. Silva-Castro, 2012

Santo, Fabio Da Silva Do Espírito, Silva-Castro, Milene Maria Da & Rapini, Alessandro, 2012, Handroanthus grandiflorus (Bignoniaceae), a new species from the semiarid region of Brazil, Phytotaxa 48 (1), pp. 1-6 : 2-6

Handroanthus grandiflorus Espírito-Santo & M.M. Silva-Castro , sp. nov. ( Figs. 1 and 2 )

Handroanthus grandiflorus is morphologically most similar to H. riodocensis and H. serratifolius , but can be distinguished from these species due to the larger corolla lobes (more than 3.8 vs. to 3 cm long).

Type:— BRAZIL. Bahia: Jacobina, on the left side of the Morro do Cruzeiro , 11°11’57.5’’S, 40°30’20.5’’W, 1 November 2010 (fl.), F. S . Espírito-Santo & R . Gonçalves-Oliveira 149 (holotype HUEFS, isotypes K, NY, SPF) .

Tree up to 8 m tall; bark slightly fissured longitudinally, reticulate, grayish; branches cylindrical and glabrescent when adult, sub-tetragonal and tomentose when young, trichomes simple and stellate, densely concentrated at the points of attachment of the petioles. Leaves 3–5-foliolate; petiole 3.2–6.1 cm long, cylindric, longitudinally sulcate, pubescent, with simple and sessile glandular trichomes; central petiolule 1.4–3.1 cm long, pubescent, trichomes simple; central leaflets 9.6–11.1 × 4.4–5.7 cm, flat, elliptical to oblongelliptic, apex acute to acuminate, margin entire or crenulate at the middle apical portion, base cuneate to rounded, chartaceous, concolorous, adaxial surface glabrous, abaxial surface glabrescent with simple and stellate trichomes restricted to the main vein; in the young leaflets, abaxial surface lepidote with sessile glandular trichomes; presence of domatia with simple trichomes; petiolules and leaflets progressively smaller towards the extremities. Inflorescences in terminal racemes, 1–4 flowers; peduncle densely tomentose, trichomes stellate and dendroid. Flowers with pedicel 1.6–3.3 cm long; calyx 1.7–1.9 × 1.1–1.6 cm, broadly campanulate, greenish-yellow, 2- or 3-lobed, irregularly divided, lobes 4.0–6.0 mm long, apex reflexed, densely tomentose at the base, sparse-tomentose towards the apex, trichomes stellate, also sparse-lepidote; corolla infundibuliform, 9.8–11.0 cm long, tube 4.8–5.5 cm long, opening 2.4–3.5 cm wide, lobes obovate, 3.9–6.1 × 3.1–4.3 cm, golden-yellow, glabrous externally, margin of the lobes and internal surface sparsevillous, simple tector trichomes ca. 2.5 mm long; stamens inserted, the free part of the dorsal stamens ca. 2.2 cm long, the free part of the ventral stamens ca. 1.6 cm long, anthers glabrous, thecae ca. 4.5 × 1.5 mm; the free part of the staminode ca. 3.0 mm long; ovary ca. 6.0 × 2.0 mm, linear-cylindric, longitudinally ribbed, glandular; nectar disk ca. 1.5 × 3.0 mm, annular, conspicuous; style ca. 2.5 cm long, glabrous, stigma ca. 3.0 × 2.5 mm long, glabrous, bifid. Capsules and seeds not seen.

Distribution and habitat:— Brazil: Bahia, Jacobina ( Fig. 3 ); in shrubby to arboreal vegetation, on sloping ground, on loamy soils and near rocky outcrops. This species is only known from a single population consisting of about eight individuals, contained within an area of approximately 18 km 2.

Conservation status:— In spite of its conspicuousness when flowering, the species has not been found at other locations, even after exhaustive fieldwork at the collection locality and within adjacent municipalities. Mining activities, tourism, agriculture, and cattle-raising are the main activities responsible for the habitat loss and deterioration of the native vegetation, thereby endangering this species. Thus, according to the IUCN criteria ( IUCN 2001), H. grandiflorus should be classified as Critically Endangered [CR B1ab (iii) + B2 ab (iii) + D1].

Etymology:— The epithet refers to the size of the corolla, whose large lobes differentiate this species.

Notes:— Among the informal groups proposed by Gentry (1992) for Tabebuia s.l., Handroanthus grandiflorus would belong to the group III, characterized by yellow flowers, pubescent campanulate calyx usually with stellate trichomes but occasionally also with simple or branched trichomes, and pubescent leaves usually with stellate trichomes or glabrescent with simple trichomes restricted to the domatia. The group III is composed by H. billbergii ssp. ampla ( Gentry 1977: 187) S.O. Grose in Grose & Olmstead (2007a: 664), H. bilbergii ssp. bilbergii ( Bureau & Schumann 1897: 319) S.O. Grose in Grose & Olmstead (2007a: 664), H. guayacan ( Seemann 1854: 180) S.O. Grose in Grose & Olmstead (2007a: 664), H. pumilus ( Gentry 1992: 244) S.O. Grose in Grose & Olmstead (2007a: 666), H. riodocensis ( Gentry 1992: 248) S.O.Grose in Grose & Olmstead (2007a: 666), H. serratifolius ( Vahl 1798: 46) S.O. Grose in Grose & Olmstead (2007a: 666) and H. uleanus ( Kraenzlin 1921: 217) S.O. Grose in Grose & Olmstead (2007a: 666).

Among the species of this group, Handroanthus grandiflorus most closely resembles H. riodocensis and H. serratifolius (Table 1). It differs from H. riodocensis due to the larger corolla 9.8–11.0 (vs. 5.5–9.0) cm long, but also by the diameter of the opening of the corolla tube 2.4–3.5 (vs. 1.5–2.0) cm, by the corolla lobes 3.9–6.1 (vs. 1.0–2.0) cm long, by the trichomes inside the calyx which are not appressed, and by the villous internal surface of the corolla (vs. glabrous). Handroanthus grandiflorus differs from H. serratifolius due to the larger calyx (1.7–1.9 × 1.1–1.6 vs. 0.8–1.1 × 0.6–1.1), but also by the shorter flower tube (4.8–5.5 vs. 6.0– 9.0 cm), and larger corolla lobes (3.9–6.1 vs. 2.0–3.0 cm). The geographical distribution of H. grandiflorus , so far restricted to the Caatinga biome, can also be used to distinguish it from the morphologically most similar species, which predominantly occur in more humid regions.

Figures

FIGURE 1. Handoanthus grandiflorus (from the holotype by Carla Teixeira de Lima). A. leaf; B. flowering branch; C. open corolla, showing stamens and staminode; D. calyx, with the stellate trichomes in detail; E. ovary and nectar disk; F. gynoecium.

FIGURE 2. Handroanthus grandiflorus (photographs by FSES; Jacobina, state of Bahia, Brazil). A. flowering branch; B. inflorescence and calyx; C. corolla (note the size of lobes).

FIGURE 3. Map of Bahia, Brazil, showing the distribution of Handroanthus grandiflorus.