Pararistolochia enricoi Luino, L. Gaut. & Callm

Iacopo Luino, Martin W. Callmander, Odile Poncy, Simona Da-Giau & Laurent Gautier, 2016, A new Pararistolochia Hutch. & Dalziel (Aristolochiaceae) from the Beanka Tsingy (western Madagascar), Candollea 71 (1), pp. 135-141 : 136-140

Pararistolochia enricoi Luino, L. Gaut. & Callm ., spec. nova

( Fig. 2 , 3 ).

Typus: Madagascar. Prov. Mahajanga: Melaky Reg., Beanka , partie S, 18̊07’22’’S 44̊33’31’’E, 300 m, 30.XI.2012, fl., Gautier, Ranirison, Hanitrarivo & Luino 5886 (holo-: G [ G00341650] !; iso-: K!, MO!, P [ P00853247 ]!, TEF!) .

Species nova quae a congeneris trichomatibus plantae partes omnes praeter caulem lignosum obtegentibus, perianthio bilobo atque foliis papyraceis deciduis perclare distat.

Climbing and ground sprawling, deciduous vine or liana. Stems to 15-25 m high, cross section flattened in the central part resulting in an 8-shape, up to 1.5 cm in width; bark of the oldest stems brown-yellow, corky, verrucate. Leaves margins entire; lamina, 4-8 X 3-6 cm, green above, paler below, papery, sparsely pubescent on both surfaces (white indumentum of simple, multicellular trichomes), shape variable, ovate to hastate; base rounded to cordate, auricles well rounded when present, sinus 0.1-1 cm deep or absent; apex rounded to slightly acuminate, sometimes apiculate; primary veins 3-5, prominent beneath, slightly elevated above, pubescent ventrally and dorsally; secondary veins reticulate; petiole slender, 0.9-2.5 cm long, 0.8-1.1 mm wide; young shoots attenuate, densely covered with a golden indumentum. Inflorescences arising from the corky stem, sometimes at ground level, solitary or fasciculate by 2-3, consisting of a 5-7 flowered raceme; rachis up to 20 cm long, with irregularly spaced internodes between 1 and 10 cm long; bracts 1-4 mm long, densely pubescent; pedicels 15-30 mm long. Flowers buds densely covered by a golden indumentum, with two bulgings corresponding to the young utricule and perianth lobes. Mature flowers up to 48 mm long overall, all the parts covered by a white indumentum; perianth tube S-curved, 15(-18) mm long, funnel-shaped, enlarging throughout and constricted below the throat, flaring from 4 mm in diam. above the utricule to up to 10 mm in diam. in its widest part; throat bright sulphur-yellow, pubescent with white 1.5 mm long setae; lobes 2, triangular to well-rounded, sometimes slightly apiculate, purple, 10 mm long, margins outwardly rolled, dark purple; utricle obovoid, externally white, punctuated with small red spots, purple veined, 11 mm long by 6 mm wide; gynostemium 2.7 mm long by 1.6 mm wide, anthers 6, 1.3 mm long, yellow, each consisting of 4 pollen sacs, stigmatic lobes 6, 1.4 mm long, green, with a short, subconical, sharp apical appendage; ovary cylindrical, 6-ribbed, densely covered by a white indument, 10 to 14 mm long. Fruits pendulous, cucumber-like, curved-cylindrical, indehiscent, woody, prominently 6-ribbed, to 5.5 cm long by 2.8 cm wide, yellow and pubescent when immature, brown and sparsely pubescent when mature. Seeds stacked in 6 simple rows, heart-shaped convex and rough above, concave and smooth below, 4 mm long by 4 mm wide.

Etymology. – The species is named in honour of the first author’s brother Enrico Luino who died in 2003 at the age of 21. Enrico triggered in him the passion for tropical botany.

Distribution and ecology. – Pararistolochia enricoi is only known from the eroded limestone formations (“Tsingy” in Malagasy) of Beanka in western Madagascar ( Fig. 1 ). Its ecology seems to be strongly related to the climax deciduous forest type, where it grows in shaded conditions. According to the collection period, anthesis takes place in November and fruits ripen between December and January. The plants presenting only young leaves at the moment of the flowering collection, we conclude that, given the papery texture and the thin lamina of the fruiting sample, the species is deciduous and that leaves are absent during the dry season, generally from May to October.

The plant-insect interactions of Pararistolochia enricoi are still unknown. In western and southern Madagascar the monospecific butterfly genus Pharmacophagus antenor (Drury, 1773) (the only representative of the tribe Troidini in Madagascar) is known to be monophagous on Aristolochia albida ( Parsons, 1996b). As documented by Parsons (1996a), the larvae of the troidine papilionid butterflies of the Australasian genus Ornithoptera feed primarily on Pararistolochia in the Australasian region. Considering the overlapping distributions of P. enricoi and Pharmacophagus antenor together with the known feeding habits of the latter, one could hypothesiZe that P. antenor larvae also feed on Pararistolochia enricoi.

Conservation status. – Pararistolochia enricoi is known only from two locations within a proposed protected area with temporary protection (Beanka). The new species is restricted to karstic limestone, an area with no evident human caused damage or alteration. Even if it currently has a very restricted range, the new species is probably under little if any threat, and is here assigned a preliminary status of Least Concern [LC].

Notes. – Pararistolochia enricoi is the second species within the family Aristolochiaceae in Madagascar. It can only be compared with Aristolochia albida Duch. but several characters clearly discriminate the new species. Pararistolochia enricoi differs from Aristolochia albida, also present in Beanka, by its habit (a woody liana up to 16 m long vs. a smaller, non-woody vine), the 8-shaped cross-section of the stem (vs. circular cross-section), the presence of indumentum on most parts (vs. glabrous), the S-shaped perianth tube with two subequal lobes (vs. straight tube with a single lobe) and the indehiscent cucumber-like fruit (vs. dehiscent basket-like fruit) ( Fig. 2 , 3 ). Furthermore, Pararistolochia enricoi is the only deciduous species of the genus and the first to be recogniZed in Madagascar. We have discussed in the introduction the reason why we consider Pararistolochia as a distinct genus from Aristolochia . However, it should be noted that even among Pararistolochia , our species has the very striking feature of a bilobed corolla (instead of a tri-lobed corolla in all other species in the genus). Hopefully molecular investigations will further confirm its generic affinities.

Paratypi. – Madagascar. Prov. Mahajanga: Beanka , partie centrale, 17̊56’53’’S 44̊28’57’’E, 190 m, 11.II.2012, fr., Rakotozafy, Bolliger & Hanitrarivo 40 ( G, TEF) ; ibid. loc., 18̊01’46”S 44̊30’18”E, 260 m, 4.XI.2015, fl., Luino 116 ( G, K, MO, P, TEF) ; ibid. loc., 18̊01’46”S 44̊30’18”E, 260 m, 15.XI.2015, fl., Luino 247 ( G, K, MO, P, TEF) ; ibid. loc., 2.XII.2015, y. fr., Luino 248 ( G, K, MO, P, TEF).

Figures

Fig. 1. – Detailed map of western Madagascar showing the distribution of Pararistolochia enricoi Luino, L. Gaut. & Callm. (stars) in Beanka, plotted on a map of forest cover in 2000 (grey) following Harper et al. (2007).

Fig. 2. – Pararistolochia enricoi Luino, L. Gaut. & Callm. A. Young shoot; B. Variable forms of the leaves; C. Inflorescence; D. Flowers detail; E. Longitudinal section of the flower showing gynostemium, utricule, and throat. [Photos: A-B, E: I. Luino; C-D: L. Gautier]

Fig. 3. – Pararistolochia enricoi Luino, L. Gaut. & Callm. A. Corky stem and leaves; B. Flower; C. Gynostemium; D. Young fruit; E. Transversal section of fruit; F. Seeds. [A-B, F: Gautier et al. 5886, G; C: Luino 116, G; D-E: Luino 248, G] [Drawings: A, C, F: S. Da-Giau; B, D-E: G. Loza]