Hildegardia dauphinensis J. G. Zaborsky, 2009

Zaborsky, John G., 2009, Hildegardia dauphinensis (Malvaceae, Sterculioideae): a new species from southeastern Madagascar, Adansonia (3) 31 (1), pp. 143-148 : 144-146

Hildegardia dauphinensis J. G. Zaborsky , sp. nov.

( Figs 2 ; 3A, B )

Differt a H. perrieri (Hochr.) Arènes pilis stellatis 18-22- ramosis, calycibus et laminis insidentibus et marginibus laminarum non revolutis.

TYPUS. — Madagascar. Toliara Province, N of Ft Dauphin [Taolagnaro], on road to Ste Luce , 6 km E of main road, main block N of road, white sand littoral forest, block S-7 of QIT-FER, 24°47’S, 47°10’E, 15 m, 13.XI.1990, leaves and flowers, G. E. Schatz, N. Dumetz, D. Faber- Langendoen, A. Randrianasolo & R. Rabevohitra 3001 (holo-, MO!; iso-, P!, TAN!).

DESCRIPTION

Deciduous tree 14 m tall. Leaf blades 13-15 × 15-16 cm, subrotund, palmately 7-veined at the base, the apex obtuse to acute, the base cordate, the margins entire and flat, not revolute, glabrous above, covered beneath with stellate hairs 0.8- 1.2 mm in diameter, each hair with 18-22 arms, hairs of domatia in axils of primary veins simple, 1 mm long. Inflorescence unknown, the flowers of the only known specimen collected from the ground. Pedicels not seen. Stipe 1.5-3 mm long; calyx 27-40 × 8-14 mm, campanulate to infundibuliform, slightly constricted at the middle, slightly flaring above, reportedly yellow-orange, thick, fleshy, the lobes 6-7.2 × 3-5 mm, narrowly triangular, acute, the entire outer surface of the calyx covered in simple and stellate hairs, simple hairs 0.4-0.6 mm long, stellate hairs 0.8-1.2 mm in diameter, the lowest 2 mm of the inside of the calyx tube filled with abundant simple hairs 2 mm long; androgynophore 28-30 mm long, covered by sparse stellate hairs 2-2.3 mm in diameter, the anthers 1-1.5 mm long, bilocular, arranged in a globose head of 5 groups, with 10 anthers per group, reportedly beige. Immature carpels 1 mm long. Fruit unknown.

REMARKS

Hildegardia dauphinensis most closely resembles H. perrieri (Hochr.) Arènes but lacks the revolute leaf margins characteristic of that species ( Arènes 1959). It also has a unique indument of multibranched stellate hairs that completely covers the leaf undersides ( Fig. 3A ). These multi-branched hairs are also interspersed among simple hairs on the calyces ( Fig. 3B ). These stellate hairs are unlike those seen in the other three Malagasy species. Each hair is stellate with 18-22 arms radiating from the center. This interesting hair structure immediately sets it apart from H. perrieri as well as the other Malagasy species. Its fruit was not collected and is unknown. The new species does not match any of the known African species treated in Dorr & Barnett (1990). These authors hypothesize that the Malagasy and African species form a natural group based on the presence of a tubular calyx, short calyx lobes, and flowering when leafless. Hildegardia dauphinensis matches these criteria as well. Wilkie et al. (2006) provided evidence that H. barteri (Mast.) Kosterm. , an African species, and H. populifolia Schott & Endl. , an Asian species, were not closely related. It is beyond the scope of this paper to clarify the circumscription of Hildegardia ; it is possible that further research may indicate the need to exclude the African and Malagasy species from this genus.

The new species, H. dauphinensis , is assessed as Critically Endangered because its EOO (Extent of Occupancy) is less than 100 km 2, it is only known to occur at a single location outside a protected area, and there is both current and predicted decline from human pressure and planned future mining activities, thus the criteria CR B1ab(i,ii,iii) of the IUCN (2001) apply.

Figures

FIG. 2. — Hildegardia dauphinensis J. G. Zaborsky: A, lower leaf surface; B, close-up of lower leaf surface showing hair structure; C, enlarged stellate hair from lower leaf surface showing multiple arms; D, flower exterior, inset showing hairs; E, flower longitudinal section showing androgynophore and inner hairs. G. E. Schatz et al. 3001. Illustration by Roger Lala.

FIG. 3. — Scanning electron micrographs:A, Hildegardia dauphinensis J. G.Zaborsky,abaxial leaf blade surface showing stellate hairs, note 18-22 arms on each hair; B, H. dauphinensis outer calyx surface showing simple and stellate hairs; C, H. erythrosiphon (Baill.) Kosterm. outer calyx surface showing stellate hairs with 4-6 arms, and wrinkled calyx surface; D, H. ankaranensis (Arènes) Kosterm. outer calyx surface showing thick, simple hairs; E, H. perrieri (Hochr.) Arènes outer calyx surface showing thick, simple hairs with scattered stellate hairs; F, H. perrieri outer calyx surface showing thick, simple hairs with scattered stellate hairs. A, B, G. E. Schatz 3001 (MO); C, H. Van der Werff et al. 12715 (MO); D, Capuron 20101 (MO); E, Ralimanana 126 (MO); F, Ralimanana 126 (MO). Scale bars: A, F, 200 μm; B-E, 500 μm.