Noronhia retusifolia Hong-Wa, 2016

Hong-Wa, Cynthia, 2016, A taxonomic revision of the genus Noronhia Stadtm. ex Thouars (Oleaceae) in Madagascar and the Comoro Islands, Boissiera 70, pp. 1-292 : 226-228

70. Noronhia retusifolia Hong-Wa , spec. nova ( Fig. 55 , 56A ).

Typus: MADAGASCAR. Prov. Toliara: Anosy, Fort-Dauphin, Ampasy Nampoana, forêt de Mandena, 24°57’10”S 47°00’10”E, 9 m, 13. II .2009, Hong-Wa 600 (holo-: MO-6615559!; iso-: G [ G00341621 ]!, P!, TAN!) .

Diagnosis

Noronhia retusifolia Hong-Wa can be distinguished from its congeners by its rugose bark, its oblanceolate, distinctly veined leaf blades that are verticillate at the tips of the branches, its retuse leaf apex, and its rugose fruits.

Description

Trees to 12 m tall, trunk to 13 cm diameter; young twigs cylindrical to subquadrangular, 2-2.7 mm diameter, glabrous; bark medium gray, rugose. Leaves opposite, verticillate at the tips of the branches, persistent; bud scales rarely persistent; blades medium green above, lighter below, oblanceolate to obovate, 6.5-9 3 2-3 cm, subcoriaceous, glabrous, domatia common, base rounded, margin slightly revolute, apex retuse, midrib sunken above, raised below, secondary veins conspicuous, 9-14 per side, 9-12 mm apart, looping 2-3 mm from the margin; petiole medium gray, 8-11 3 1.5-2.5 mm, entirely woody, glabrous. Flowers unseen, but infructescence thyrsoid. Fruiting pedicel 5-8 3 2-2.5 mm; young fruits green, reddish brown when mature, ovoid, 14.5-17 3 11-12 mm, rugose, apex flat to bluntly pointed; dry pericarp 1.7-2 mm thick; endocarp woody; seed 9-10 3 4-8 mm.

Etymology

The specific epithet refers to the distinctly retuse apex of the leaf blade, which characterizes this species.

Distribution, ecology and phenology

Noronhia retusifolia occurs on unconsolidated sands in the littoral forest of Mandena, north of Fort-Dauphin in the south ( Fig. 49 ). It has been collected in fruits in February.

Conservation status

Noronhia retusifolia is known only from a single collection from a small remnant of littoral forest (Mandena) in southeastern Madagascar, which has just received a permanent protection status that does not, however, preclude continued habitat degradation resulting from illicit exploitation in the context of a growing population. The surrounding areas are also being converted for ilmenite exploitation, leaving this littoral forest patch even more isolated from such other patches. Although the individual sampled appears growing close to the QMM-Rio Tinto nursery where GPS data were recorded for a group of specimens, it actually occurs farther in an area that is probably not under constant surveillance. In addition, this species appears to be rare as discussed below. Therefore, N. retusifolia is assigned a preliminary status of “Critically Endangered” [CR B2(iii); D].

228 Boissiera 70

Notes

Noronhia retusifolia most closely resembles N. orientalis , from which it differs by having leaves that are oblanceolate to obovate (vs. oblong to obovate), flat (vs. sub-bullate), and 9 3 3 cm (vs. 15 3 5 cm), shorter petioles (less than 11 mm vs. up to 22 mm), and fruits that are rugose (vs. smooth to sometimes slightly rugose). The rugose bark, oblanceolate, distinctly veined leaf blades that are verticillate at the tips of the branches, retuse leaf apex, and rugose fruits characterize this species. Noronhia retusifolia is known only from the type specimen and appears to be rare. This is rather surprising given the level of botanical inventory done within the small littoral forest of Mandena since the late 1940s. Indeed, more than 2,000 plant collections have been made from this site, of which about 20 are identified as Noronhia . It is, however, possible that the numerous unidentified [and unfiled] collections of the Service Forestier de Madagascar held in the Paris herbarium include other representatives of this species.

Figures

Fig. 55. Noronhia retusifolia Hong-Wa.

Fig.56.Photographs of Noronhia Stadtm.ex Thouars

Fig. 49. Distribution maps of species of Noronhia Stadtm.ex Thouars. N. pervilleana (KnobL.) H. Perrier to N. seyrigii H. Perrier.