Randrianasolo, A. & P. P. Lowry II (2015). A new species of Operculicarya H. Perrier (Anacardiaceae) from western dry forest of Madagascar. Candollea 70: 57–60. In English, English and French abstracts.
A new species of Operculicarya H. Perrier (Anacardiaceae) is described from material collected in dry forest on karstic limestone in western Madagascar, bringing the total number of species in the genus to nine. Operculicarya calcicola Randrian. & Lowry is distinguished from the other members of the genus by the size and shape of its leaves and leaflets, the structure of its infructescence, and the size of its fruits. An illustration is provided along with a distribution map and preliminary assessment of its risk of extinction following the IUCN Red List criteria, which indicates a status of Least Concern.
Introduction
The genus Operculicarya H. Perrier (Anacardiaceae) has been the subject of a pair of taxonomic revisions during the last two decades, the first by Eggli (1995), who recognized six species, including four he described as new, and the second by Randrianasolo & Lowry (2006), who re-examined species limits and described two additional novelties, bringing the total number of species to eight, all of which occur on Madagascar, with one, O. gummifera (Sprague) Capuron, also present in the Comoro Islands. As part of our ongoing study of Malagasy Anacardiaceae, we have systematically been examining newly collected herbarium material resulting from the extensive inventory work conducted throughout Madagascar by botanists from various institutions, which has regularly led to the discovery of new taxa. Here we describe a distinctive new species of Operculicarya restricted to areas of karstic limestone (referred to locally as “tsingy”), in western Madagascar, in particular in the Beanka forest (Gautier et al., 2013) where most of the specimens, including the type, were collected. This species was previously known only from one fertile and two fragmentary, unidentifiable specimens.
Systematics
Operculicarya calcicola Randrian. & Lowry, spec. nova (Fig. 1).
Typus : Madagascar. Prov. Mahajanga: Région Melaky, Beanka, S de la Kimanambolo, 18°07′14″S, 44°33′34″E, 350 m, 25.XI.2014, fr., Gautier et al. 5829 (holo-: G [G00377897]!; iso-: BR, K, MO-6605509!, P [P00641020]!, TAN).
Operculicarya calcicola Randrian. & Lowry differs from its most similar congener, O. gummifera (Sprague) Capuron, by its larger leaflets [(2.5-) 6-11 × (1.3-)2.5-4.7 vs. (2)3-6.3 × (0.9)1-1.9 cm] and fruits [10-12 × 7-10 × 5-7 vs. 6-9 × 5-7× 3-5 mm], as well as the thickness of its infrutescence axis [0.9-1.3(-1.8) vs. 0.3-0.9(-1.3) mm].
Small to medium trees ca. 5–10 m tall, trunk ca. 11–20 cm in diam. with smooth bark; twigs short-lanate. Leaves imparipinnate, alternate and usually well-spaced on long shoots, more closely clustered on lateral short shoots, (14-) 19-28.5 cm long; petiole 5–8.5 cm long, short-lanate; rachis not winged, terete, short-lanate; leaflets (9-)11-13, lateral ones opposite, petiolules 2–5 mm long, short-lanate, blade membranaceous to chartaceous, ovate, (2.5-)6-11 × (1.3-)2.5-4.7 cm, median ones largest, discolorous, dark greenish brown to dark green above when dried, paler green beneath, densely lanate on both surfaces when young, with longer and somewhat denser trichomes along the midvein and secondary veins, glabrescent on upper surface except along midvein and secondary veins, venation craspedodromous, tertiary venation visible, more so on lower surface, base oblique to subcordate, asymmetric in lateral leaflets, margin entire, apex acuminate, the acumen rounded. Flowers unknown. Infructescence axes 2-7.5(-17) cm long, 0.9-1.3(-1.8) mm in diam. at base; pedicel ca. 1–3 mm long, glabrous. Fruits 6-8(-16) per infructescence, ellipsoid, slightly compressed laterally, 10-12 × 7-10 × 5-7 mm; endocarp bony, with a single operculum.
Distribution and ecology. — Operculicarya calcicola is only known from dry, deciduous forest on karstic limestone (“tsingy”) in western Madagascar (Fig. 2), at elevations between 50 and 600 m. The flowers of this species are as yet unknown, but fruiting material has been collected in November and December.
Conservation status. — Operculicarya calcicola has an extent of occurrence (EOO) of 1,426 km2 and would thus qualify as Endangered under the Criterion B1 of the IUCN Red List (IUCN, 2012) if other qualifying conditions were met. However, as O. calcicola is restricted to karstic limestone areas, one of the few natural habitats in Madagascar that does not appear to be subjected to noticeable human-caused destruction or alteration, it may well be under little if any threat, and should thus be assigned a preliminary status of Least Concern [LC].
Notes. — Using the key provided by Randrianasolo & Lowry (2006), material of this new species would be identified as O. gummifera (Sprague) Capuron. It can, however, be distinguished by several features, as summarized in Table 1.
All but three of the known collections of O. calcicola were made since Randrianasolo & Lowry (2006) completed their review of the genus. The two oldest gatherings (Leandri 2017 and Service Forestier 6778) were not cited by them because they are fragmentary and could not be assigned with confidence to any of the eight species they recognized, whereas the most recent one (Jongkind et al. 3228) was regarded as a somewhat atypical individual of O. gummifera.
Paratypi. — Madagascar. Prov. Mahajanga: Region Melaky, Tsingy de Bemaraha, S of the Manambolo River, 19°09′S 44°09′E, 50 m, 26.XI.1996, fr., Jongkind et al. 3228 (G [G00404134], MO-5968354, P [P04800703], TAN, WAG); env. de Tsiandro (Ouest), forêt de Behandrao, [18°49′37″S 44°52′25″E], 500–600 m, 25.XI-3.XII.1952, fr., Leandri 2017 (P [P00633854, P00633857]); aux env. de Tsiandro, [18°49′37″S 44°52′25″E], 4.XII.1952, fr., Service Forestier 6778 (P [P00120510, P06242028, P06633856]); Beanka, partie centrale, Ambinda Nord, 17°55′48″S 44°28′34″E, 223 m, 16.XI.2011, fr., Gautier et al. 5625 (G [G00376040], MO-6605511, TAN); forêt d'Amboloando, Tsingy de Beanka, 18°04′35″S 44°32′02″E, 269 m, 12.XI.2012, fr., Rakotovao et al. 6185 (G [G00377809], MO-6605512, TAN); ibid. loc., 18°04′56″S 44°32′20″E, 269 m, 13.XI.2012, fr., Rakotovao et al. 6213 (G [G00377810], MO-6605510, TAN).
Fig. 2.
Geographic distribution of Operculicarya calcicola Randrian. & Lowry; darker areas indicate remaining natural vegetation (insert map shows the bioclimatic zones of Madagascar (after Cornet, 1974; see Schatz, 2000).
Table 1.
Morphological features distinguishing Operculicarya calcicola Randrian. & Lowry from O. gummifera (Sprague) Capuron.
Acknowledgements
We wish to thank Roger Lala Andriamiarisoa for the fine illustration, Martin Callmander for assistance with obtaining loans, scans and bar codes of specimens from G, George Schatz for valuable help with the risk of extinction assessment, Tantely Raminosoa for preparing the species distribution map, and the staffs of the Herbier National in Paris (P) and the Botanical and Zoological Park of Tsimbazaza herbarium in Antananarivo (TAN) for providing access to their collections. We gratefully acknowledge courtesies extended by the Government of Madagascar (Ministère de l'Environnement, de l'Écologie, de la Mer et des Forêts (MEEMF). Finally we thank Laurent Gautier and Roy Gereau for helpful comments on an earlier version of this manuscript that led to its improvement.
