Prosopanche caatingicola R.F.Machado & L.P.Queiroz, 2012

Machado, Ricardo Ferreira & Queiroz, Luciano Paganucci De, 2012, A new species of Prosopanche (Hydnoraceae) from northeastern Brazil, Phytotaxa 75 (1), pp. 58-64 : 59-61

Prosopanche caatingicola R.F.Machado & L.P.Queiroz , sp. nov. ( Figs. 1–2 ).

Similar to Prosopanche bonacinai by its mostly trigonous stem and relatively small flowers but distinguished by the shorter perigonial tube (5–10 mm long in P. caatingicola vs. 12–80 mm long in P. bonacinai ), shorter tepals (18–22 mm vs. 35–55 mm long), smaller synandrium (9.0– 9.5 mm vs. 15.0–25.0 mm long), anthers with fewer thecae (5–8 vs. 20–30), and staminodes split in two oblongoid bodies (vs. staminodes entire and bilobed at the apex).

Type: ⎯ BRAZIL. Bahia: São Gabriel, Alto da Jurema , 11°11’42”S 41°50’29”W, 05 April 2009, Machado, Rocha, Rocha & Rocha 652 (holotype HUEFS!; isotypes C!, CEPEC!, CORD!, K!, LIL!, MO!, NY!, RB!, SI!, SP!) .

Perennial holoparasite herb, hypogean, achlorophyllous; rhizomes 3–4-angular, 8–10 mm diam., fleshy, haustorial rudiments numerous on the angles 3–5 mm apart. Leaves and bracts absent. Flowers isolated, bisexual, emergent; pedicel 27–30 × 7–8 mm; perigonial tube 5–10 mm long; tepals 3, outer surface brown, inner surface ochre, valvate, fleshy, 18–22 × 4–14 mm, linear, oblong or ovate-oblong; anthers 3, with 5–8 thecae, joined in an oblongoid, dark-red synandrium, 9.0–9.5 × 4.0–5.0 mm, filaments 2–3 × 2 mm; staminodes reflex, sessile, bifid, split in two oblongoid fleshy bodies, c. 3.0–3.1 × 1.0– 1.5 mm at the base; ovary inferior, 15–20 × 12–17 mm, ellipsoidal or almost spheroidal, ovules much reduced, numerous, embedded in fleshy, parietal placenta, stigma surface triradiate, lamellae not seen. Fruit hypogean, 40–47 × 30–35 mm, indehiscent, berry-like, globose or ellipsoid, pericarp dry, surface rugose, ripe placentae fleshy, bright white, embedding numerous seeds.

Distribution, habitat, and hosts:— The species is only known from a small area in the municipality of São Gabriel, Bahia (11°11’45”S 41°50’10”W). Flowering plants were observed in March and April, and ripe fruits were found in July and August. It occurs in the seasonally dry tropical forest, known as caatinga. Local climate is mostly semi-arid, classified as CwB under the Köppen climate classification, with the mean annual temperature of 23ºC, total rainfall of 500 mm.year -1 and a long dry season between May and September ( Oliveira 2009). Soil is mostly derived from crystalline bedrock and limestone outcrops. Vegetation is characterized by a low and open canopy and deciduous shrubs and trees, most with spines or prickles.

Legumes are a dominant group in caatinga vegetation ( Queiroz 2006, Queiroz & Lavin 2011). Prosopanche caatingicola was found in association with three mimosoid legume species: Parapiptadenia zehntneri ( Harms 1924: 712) Lima & Lima (1984: 26), Mimosa ophthalmocentra Martius ex Bentham (1875: 415) and Calliandra depauperata Bentham (1875: 546) .

Conservation status:— Although it was recorded in only a small area of ca. 200 m 2, P. caatingicola should be classified as DD (data deficient) according to the IUCN criteria ( IUCN 2010) because it could potentially have a wider range. The plant is visible only when flowers are exposed and, thus, is difficult to locate.

Etymology and ethnobotany:— The specific epithet highlights the fact that the new species was found in the caatinga vegetation. Local people call this plant ‘gemedeira’, the one that makes the soil groan, believing that on Good Friday the plant makes the soil tremble and groan. Unlike other species of Prosopanche , no part of the plant of P. caatingicola is used as food by local people.

Additional specimens examined (paratypes):— BRAZIL. Bahia: São Gabriel, Alto da Jurema , 11°11’45”S 41°50’10”W, 10 August 2010, Machado, Rocha & Rocha 653 ( CTES, F, HUEFS, MBM) ; same locality, 11 June 2011, Machado 654 ( B, HUEFS, SPF) ; same locality, 9 September 2012, Machado 655 ( HUEFS) .

Notes:— Prosopanche caatingicola is closely related to P. bonacinai , both sharing the mostly trigonous rhizome and reproductive structures smaller than those of P. americana and P. costaricensis ( Table 1). They can be differentiated by the number of thecae (5–8 thecae in P. caatingicola vs. 20–30 in P. bonacinai ), shape and division of staminodes (split in two oblongoid bodies vs. entire or bilobed at the apex) and shape of the fruit (almost globose or ellipsoidal vs. obovoidal or pyriform). Prosopanche caatingicola also has the smallest flowers in the genus ( Table 1) and was observed to be associated with three mimosoid legumes. No legume host has been cited for P. bonacinai , and it is reported to parasitise plants of several other families, Anacardiaceae , Apiaceae , Aquifoliaceae , Asteraceae , Chenopodiaceae , Malvaceae , Rhamnaceae and Solanaceae ( Cocucci 1965, Cocucci & Cocucci 1996).

Figures

FIGURE 1. Prosopanche caatingicola. A. Habit, showing the 3–4-anguled rhizomes, globose fruit and root of the host (arrow; scale bar = 1 cm). B. Flower (scale bar = 1 cm). C. Tip of the flower, with a tepal removed to show synandrium (scale bar = 0.4 cm). D–E. Flower, with two tepals removed, showing synandrium and bilobed staminodes (scale bar = 0.4 cm). F. Detail of bilobed staminodes (scale bar = 1.7 mm). Drawn by Klei Sousa, all from Machado et al. 652 except 1B from Machado et al. 653.

FIGURE 2. Prosopanche caatingicola. A–B. Plant removed from the ground, showing an underground flower bud (A) and a piece of the host root (B). C. Underground fruit exposed by removing its surrounding. D–E. Ripe fruit opened (E) to show the placenta and abundant seeds. F. Flower bud. G–J. Tip of the flower with one (H) or two (I–J) tepals removed to show synandrium (H–I) and staminodes (J). Photos by Ricardo Machado.