Pentachlaena pestita Andriam., Lowry & G.E. Schatz

Tefy H. Andriamihajarivo, Porter P. Lowry Ii & George E. Schatz, 2016, Endemic Families of Madagascar. XIV. a New Restricted Range Species of Pentachlaena H. Perrier (Sarcolaenaceae) from Central Madagascar, Candollea 71 (2), pp. 166-172 : 168-172

Pentachlaena pestita Andriam., Lowry & G.E. Schatz , spec. nova

( Fig. 1 , 2 ).

Typus: Madagascar. Prov. Fianarantsoa: Amoron’i Mania Region, Ambositra , commune rurale Ihadilagnana, Mt. Ambatolahinanahary , 20̊26’43’’S 47̊03’42’’E, 1303 m, 4.XI.2014, fl., Ħndriamiðajariυo et al. 1907 (holo-: MO-6684230 !; iso-: G!, MO-6685745!, P [ P 01066023]!; TAN!).

Haec species Pentacðlaenae latifoliae H. Perrier simillima, sed ab ea foliis majoribus (7.7­13.8 × 5.8­11.8 υs. 4.5­ 8.8 × 3.5­7 cm) υenis secundariis in paribus (10 ad) 14 ad 16 (υs. 7 ad 10) plerumque craspedodromis interdum distaliter subbrocðidodromis (υs. semper brocðidodromis), foliis abaxialiter necnon petiolis caulibus juυenilibus inflorescentiae axibus bracteis sepalis et fructu tricðomatibus stellato­strigosis c. 0.2­0.3 mm in diam. dense υestitis (υs. tricðomatibus stellato­punctatis <0.1 mm in diam. sparsim modiceυe indutis) atque petalis majoribus (1.6­2.2 × 1­1.3) υs. 1.2­2.1 × 0.8­1.4 cm) distinguitur.

Sðrub, 0.5-1.5 m tall. Leaυes ovate to oblong, rarely orbicular, coriaceous, (5.1-)10-13.8 × (4.3-)8-11.8 cm, weakly discolorous, with dense stellate-strigose trichomes c. 0.2- 0.3 mm in diam. on abaxial surFace, glabrous on adaxial surFace, base usually subcordate, rarely rounded, margin entire, apex retuse to emarginate, midvein channeled above, raised below, venation craspedodromous, occasionally approaching brochidodromous in distal 2 to 5 major secondary veins, with (10 to) 14 to 16 pairs oF secondary veins, weakly impressed above, raised below; petiole (1.3-)1.8-2.2(-2.8) cm long, 2-3 mm in diam., densely stellate-strigose, adaxially canaliculate. Inflorescences axillary and terminal, usually 2-flowered (occasionally 1-flowered), peduncles 1-3 mm long, densely stellate-strigose; flowers subsessile, bracts (3-)4-6(-8) × 1 mm, narrowly lanceolate, margin entire to slightly dentate, sparsely stellate-strigose; involucre scale-like, densely stellate-strigose; sepals 5, quincuncial, unequal in size, united at the base, 0.4-0.6(-0.8) × 0.8-1 cm, stellate-strigose on outer surFace, glabrous and with evident reticulate veins on inner surFace; petals 5, quincuncial in bud, white, obovate, glabrous, Free, with evident actinodromous and reticulate venation, 1.6-1.7(-2.2) × 1-1.1 (-1.3) cm, base cuneate, apex truncate, extrastaminal disc 1-1.2 mm high, with a sinuate margin; stamens 40 to 70 or more, filaments (0.5-)0.7-0.8(-0.9) mm long, anthers ellipsoid, 0.7-1 mm long, introrse, basifixed; ovary globose, densely stellate-strigose, 2.4-2.7 × 3-3.5 mm, locules 5, style glabrous, ovules 6 per locule, 1.5- 1.6 mm long, 0.5 mm in diam., stigma capitate, light green, 5-lobed, margins oF the lobes distinctly undulate. Fruits obloid, light brown to orangish, 3 × 2-2.5 cm, flattened at the apex and the base, ridged, dehiscent, exocarp thin, densely stellate-strigose, endocarp thin, seeds 1 per locule, brown, slightly flattened, c. 1.3 cm long.

Etymology. – The epithet ‘vestita’ reFers to the dense stellate strigose indument on the abaxial surFace oF the leaves as well as the petioles, young stems, inflorescence axes, bracts, sepals, and Fruits.

Distribution and ecology. – Pentacðlaena υestita is restricted to Mt. Ambatolahinanahary, located near the Mania River in the north-western part oF Ambositra district in central Madagascar, some 30 km to the south oF the Ibity massiF, where P. latifolia , which it most closely resembles, occurs ( Fig. 3 ). It grows on quartzite substrate in an open matrix oF wooded grassland and bushland/Tapia woodland at elevations between 1250 and 1500 m. Pentacðlaena υestita is known From only seven collections. Material in bud and flower has been gathered in October and November, and the single Fruiting collection was made in January.

[A-F: Andriomihojorivo 1907, G, Rovololomonono et ol. 57, TAN] [Drawing: R.L. Andriamiarisoa]

Vernacular name. – Mananamba.

Conserυation status. – With an extent oF occurrence oF <100 km2, an area oF occupancy oF <10 km2, and two locations with respect to the most serious threat, which is fire, along with an estimated population size oF more than 250 but probably less than 2,500 mature individuals, we assign a preliminary risk oF extinction status oF “Endangered” [EN B1a b(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v); C2a(ii)] using the IUCN Red List (IUCN, 2012).

Notes. – Pentacðlaena υestita most closely resembles P. latifolia , which also occurs in central Madagascar, primarily on and around the quartzitic Ibity MassiF some 30 km to the north ( Fig. 3 ). These two species both have ovate to oblong, weakly discolorous leaves with a retuse to emarginate apex, axillary and terminal inflorescences with one or two flowers subtended by entire or slightly dentate bracts, and occur on quartzite substrates. Our new species can, however, be distinguished by a suite oF characters, as summarized in Table 1 .

Pentacðlaena υestita, like P. latifolia , is clearly fire tolerant, as are most oF the other species that have been able to survive in Madagascar’s wooded grassland and bushland/Tapia woodland habitats. The increased Frequency oF fires in these areas above historical pre-human levels has likely reduced the number oF sites where individuals oF P. υestita can persist and has probably also stunted their growth, preventing them From reaching their maximum potential height ( Fig. 2 C, D).

Lowry et al. (2000), in their revision oF Pentacðlaena, assigned Perrier de la Bâtðie 2112 From the Mania River to P. latifolia , having overlooked the Fact that this collection exhibits the distinctive Features that characterize P. υestita. In re-examining the holdings oF other species oF Pentacðlaena in the Paris herbarium to compare them with the material oF our new species, we Found that another collection, Perrier de la Bâtðie 1998, made in January 1913, comprises a mixed gathering oF material clearly belonging to P. υestita and to P. latifolia . The label data accompanying the two specimens oF this gathering indicate that it was collected on Mt. Ibity, where P. latifolia is abundant, suggesting that some Fragments oF P. υestita, almost surely belonging to Perrier de la Bâtðie 2112, were accidentally mounted along with the material oF Perrier de la Bâtðie 1998. While it is not out oF the question that the two taxa were growing in sympatry at Ibity, this seems highly unlikely given that no individuals resembling P. υestita have ever been observed intermingled in the population oF P. latifolia and that no plants oF P. υestita have ever been collected at Ibity, which Further supports our interpretation that they represent two geographically distinct taxa. A similar case oF closely related but morphologically distinct species restricted to wooded grassland and bushland/Tapia woodland on quartzite and marble substrates in central Madagascar can be Found in the genus Pðilgamia Baill. (Malpigðiaceae), whose Four members all occur in this same type oF habitat and have clearly diversified within a limited geographic area ( Arènes, 1950; Madagascar Catalogue, 2016).

Paratypi. – Madagascar. Prov. Fianarantsoa: Région Amoron’i Mania, Ambositra, Comm. Ihadilagnana, à l’W de Volondoha, 20̊25’49’’S 47̊04’49’’E, 1254 m, 19.I.2005, Fr., Ħndriamiðajariυo et al. 566 (MO, TAN); Ihadilagnana, W d’Ambositra, Mt. Ambatolahinanahary, 20̊26’05’’S 47̊03’38’’E, 1491 m, 25.III.2006, bud, Ħndriamiðajariυo 874 (TAN); ibid. loc., same date, fl., Ħndriamiðajariυo 875 (TAN); Ambohipiandrianana-Ambohibary, Ihadilagnana, Ambositra, 20̊26’43’’S 47̊03’42’’E, 1303 m, 04.XI.2014, bud & fl., Ħndriamiðajariυo et al. 1908 (G, MO, P, TAN); sur la Mania, bois à Tapia, c. 1200 m, VI.1912, fl., Perrier de la Bâtðie 2112 (P [3 sheets]); Ihadilagnana, massiF d’Ambatolahinanahary, 20̊26’26’’S 47̊03’31’’E, 1346 m, 20.I.2006, bud, fl., Raυololomanana et al. 57 (MO, P, TAN).

Figures

Fig. 1. – Pentochloeno vestito Andriam., Lowry & G. E. Schatz. A. Flowering branch; B. Detail of indument on lower leaf surface; C. Detail of upper leaf surface; D. Flower; E. Detail of androecium; F. Detail of gynoecium; G. Fruit.

Fig. 2. – Photographs of Pentochloeno vestito Andriam., Lowry & G. E. Schatz. A. Flowering branch; B. Close-up of flower (note dense indument on lower surface of leaf); C. Adult plant; D. Habitat of type locality, with open wooded grassland and bushland / Tapia woodland and rocky quartzite substrate. [Photos: T. Andriamihajarivo]

Fig. 3. – Geographic distribution of Pentochloeno vestito Andriam., Lowry & G. E. Schatz (stars) and P. lotifolio H. Perrier (circles).

Tables

Table 1. – Key characters distinguishing Pentochloeno vestito Andriam., Lowry & G. E. Schatz from P. lotifolio H. Perrier

	P. vestitơ	P. lơtifoliơ
Largest leaf blade
length [cm]	(7.7-)9.5-13.8	4.5-7.5(-8.8)
width [cm]	(5.8-)6.5-11.8	3.5-5.7(-7)
Indument on abaxial leaf surface	Densely stellate-strigose, trichomes c. 0.2-	Sparsely stellate-punctate, trichomes <0.1 mm
	0.3 mm in diam., on all veins (incl. tertiary),	in diam., along midvein and major secondary
	almost completely obscuring leaf surface	veins, occasionally on inter-secondary veins,
		not obscuring leaf surface
Leaf venation	Craspedodromous, occasionally approaching	Brochidodromous
	brochidodromous in distal 2 to 5 major secondary
	veins
Number of pairs of secondary	(10-)14-16	7-9(-10)
veins per leaf
Indument on twigs and petiole s	Densely stellate-strigose, almost totally	Sparsely to moderately densely stellate-
	obscuring surface	punctate, covering <50% of the surface
Petal size [cm]	1.6-1.7(-2.2) X 1-1.1(-1.3)	1.2(-2.1) X 0.8(-1.4)