Danais rakotovaoi C. M. Taylor

Taylor, Charlotte M. & Rogers, Zachary S., 2013, Six new species of Danais Vent. (Rubiaceae, Danaideae) from Madagascar, Candollea 68 (1), pp. 167-180 : 176-177

5. Danais rakotovaoi C. M. Taylor , spec. nova

( Fig. 6D, E ).

Typus: MADAGASCAR. Prov. Antsiranana: SAVA Region, Andapa, Doany, Andranomololo , forêt de moyenne altitude située à 10 km au Sud Ouest du village d’Andranomololo, Andramanalana, 14°29’55”S 49°33’43”E, 1098 m, IV.2006, fl., Rakotovao & al. 3222 (holo-: MO-6082545 ! ; iso-: P, TAN) .

Haec species a congeneris stipulis grandibus marginibus serratis usque breviter multifidis, inflorescentia axillari floribus in cymas densas rotundatas dispositis atque corolla violacea 9-10 mm longa distinguitur.

Woody lianas or climbing shrubs; stems to 6 m long, densely strigillose to glabrous, rounded. Leaves opposite; blades obovate or oblanceolate to elliptic-oblong, 3.8-17.5 × 2-5.5 cm, at base acute to cuneate, at apex acute to acuminate with tips 3- 5 mm, drying papery, adaxially and abaxially densely and rather uniformly puberulous or strigillose to glabrous throughout, with margins plane; secondary veins 10 to 11 pairs, weakly to strongly uniting with each other near margins at least in distal portion of blade, intersecondary veins not or shortly developed, adaxially costa prominent and remaining venation plane or sometimes secondary and loosely reticulated tertiary veins thickened, abaxially costa and secondary veins prominent, loosely reticulated tertiary venation thinly prominulous, and quaternary venation not visible or thickened and densely reticulated. Petioles 5-26 mm, glabrous to densely strigillose. Stipules interpetiolar, persistent at least on distalmost 3 to 5 nodes, ovate to triangular, 4-16 mm, abaxially glabrous to densely puberulous, at apex narrowly acute to acuminate, margins irregularly shortly serrate to shortly laciniate or multifid. Inflorescences axillary, cymose to paniculiform, rounded in outline, 2.5-8 × 2-6 cm (including peduncles), several- (ca. 30) to multiflowered (ca. 90), branched to 1 to 2 orders, with axes cymose, densely strigillose to glabrous, with basalmost secondary axes subtended by ovate foliaceous bracts (or reduced leaves) 0.7-1.6 × 0.8-1.3 cm on stipes (or petioles) 2-5 mm; other bracts stipuliform or narrowly triangular to linear, 0.8-5 mm. Flowers in congested cymes of 5 to 7 and sessile to subsessile or shortly pedicellate on pedicels to 1 mm, with floral biology unknown; hypanthium obconic to ellipsoid, ca. 1 mm, densely strigillose to glabrous. Calyx limb divided nearly to base, glabrous to densely strigillose, lobes 5, narrowly triangular, 2-4 mm, acute. Corolla salverform, violet, externally glabrous, internally glabrous except pilose inside top of tube around anthers, tube ca. 7 mm, ca. 0.6 mm diam. at bottom, ca. 0.8 mm diam. at top, at base irregularly fenestrate with 5 slits, each slit 0.5-1 mm, slits often unequal in size on an individual flower, lobes 5, narrowly triangular, ca. 2 mm, acute and smooth at apex. Stamens 5, inserted below top of corolla tube, anthers ca. 1.2 mm, included and subsessile, color not noted. Stigmas 2, ca. 2 mm, exserted, style ca. 9.5 mm. Capsules and seeds not seen.

Names. – The scientific name created here for this species honors Mr. Charles Rakotovao, collector of the type specimen of this elegant species and one of the Missouri Botanical Garden’s resident field botanists. Mr. Rakotovao has extensively documented Madagascar’s flora with excellent specimens collected during numerous explorations made throughout the island. The vernacular name “Vahibivoraka” was noted on the specimen Randriamanarivo & al. 39 and is in the Betsimisaraka dialect. The local name roughly translated into English means “big liana with a soft consistency.” The reference to the soft quality of the plant may indicate that the stems can be compressed by squeezing between the fingers (A. Randrianasolo, pers. comm.).

Habitat and distribution. – This species is documented from humid forests at 720-1098 m in east-central to northeastern Madagascar, in Antsiranana Province (SAVA Region) and Toamasina Province (Analanjirofo and Antsinanana Regions; Fig. 2 , humid bioclimatic zone).

Conservation status. – Danais rakotovaoi has an EOO of 711 km 2, which meets the criterion for Endangered; an AOO of <500 km 2, which also meets the criterion for Endangered; and three subpopulations. The species is known from three widely separated collections. One of the localities apparently falls just inside the boundaries of a currently protected area (Zahamena National Park), and the northernmost collection was made approximately 3 km outside of the boundaries of a second protected area (Marojejy National Park) and it is quite plausible that the species occurs inside that park as well. The habitat of this species is already significantly fragmented and expected to diminish further in quality. Danais rakotovaoi is assigned a preliminary conservation status of Endangered due to its limited distribution and threatened habitat [EN B1ab(i,ii,iii,iv)+2ab(i,ii,iii,iv)].

Notes on morphology, classification and similar species. – Danais rakotovaoi is characterized by its well developed stipules with shortly laciniate margins; its axillary, generally rounded inflorescences; its rather well developed narrow calyx lobes; and its medium-sized violet corollas. The fruits and seeds of this species have not been examined, but all other available features including the climbing habit support the classification of D. rakotovaoi in this genus.

The stipules of this new species are unusual in Danais , and similar only to those of D. antilahimenae ; however D. antilahimenae can be separated from D. rakotovaoi by its much larger inflorescences with prolonged spiciform axes, its shorter calyx lobes, and its longer corollas. Only one flowering collection of D. rakotovaoi has been seen, which has flowers that are similar to the long-styled form of distylous species of Danais . This new species is unusual in Danais in the distribution of its leaf pubescence, which is generally uniform in density and trichome size throughout the blade, while in other species of the genus the leaf pubescence is usually denser and composed of longer trichomes on the veins than on the lamina. This new species appears also to be similar to the poorly known species D. coerulea Homolle ex Cavaco based on published descriptions. Danais coerulea is not well characterized but was described as having significantly larger corollas, 20-25 mm long in overall length (i.e., tube plus lobes), vs. ca. 9 mm in overall length in D. rakotovaoi .

Paratypi. – MADAGASCAR. Prov. Toamasina: Analanjiforo, Vavatenina, Miarinarivo, Anamborano, Ambinanini, Sahavarina , à l’interieur de l’AP à 1 km de la limite, 17°41’08”S 48°59’43”E, [no elevation], 16.VI.2001, fl., Randriamanarivo & al. 39 ( MO!, TAN) ; Antsinanana, Brickaville, Maroseranana, Andeka, Amparamanambola , à 6 heures de marches au N d’Andeka, route vers Besaha, 18°24’47”S 48°49’42”E, 720 m, 29.X.2005, bud, Andriamihajarivo & al. 684 ( MO!, TAN) .

Figures

Fig. 6. – Danais randrianaivoi C. M. Taylor. A. Flowering branch; B. Portion of inflorescence with four flowers from which the corollas have fallen; C. Corolla at anthesis, separated from rest of flower and showing the fenestrate base. – Danais rakotovaoi C. M. Taylor. D. Flowering branch; E. Flower at anthesis. [A-C: Randrianaivo 664, MO; D-E: Rakotovao & al. 3222, MO] [Drawing: C. M. Taylor]

Fig. 2. – Distribution of Danais antilahimenae C. M. Taylor (triangles) and Danais rakotovaoi C. M. Taylor (stars), mapped over the outlines of the five simplified bioclimatic zones of Madagascar of SCHTZ (2000, following CORNET, 1974).