Badula ovalifolia A.DC.

Florens, F.B.V., Baider, C. & Bosser, J. (2008). On the Mauritian origin of Badula ovalifolia (Myrsinaceae), hitherto believed extinct, with complementary description. Kew Bulletin 63: 481. https://doi.org/10.1007/s12225-008-9069-z

Note

All known plants of Badula ovalifolia grow at about 600 m altitude, on humic ferruginous latosols (Parish & Feillafé 1965), in the super humid region (Halais & Davy 1969). In Macchabé, it occurs in native forest about 18 m tall dominated by Nuxia verticillata Lam. (Stilbaceae), Syzygium glomeratum DC. (Myrtaceae) and Mimusops maxima (Poir.) R. E. Vaughan (Sapotaceae). In Brise Fer, the canopy is about 15 m tall, and dominated by Securinega durissima J. F. Gmel. (Euphorbiaceae), Diopyros tessellaria Poir. (Ebenaceae) and Eugenia pollicina Guého & A. J. Scott (Myrtaceae). Both areas are invaded by alien species of which Psidium cattleianum Sabine (Myrtaceae) and Ligustrum robustum Thwaites subsp. walkeri (Descne.) P. S. Green (Oleaceae) are the most dominant comprising over 80% of woody stems above 1.3 m.

Phenology

In recent collections, flowers were found from the end of January to April. Bojer (1837) mentions flowering from February to May. Fruits reach mature size within a month, but need a further eight months or so to ripen (between October to January). At each site, the plants grow in clumps, within an area of about 10 m2.

Conservation

All adult specimens show signs of heavy damage to major stems apparently caused by boring insects resulting in stems dying above 1.5 – 2 m height and resprouting from below. Badula ovalifolia was classified as an extinct Reunion species in the 1997 IUCN Red List (Walter & Gillet 1998). It is now known in the wild from four adults, one sapling and one seedling. Since 1997, two mature individuals have died and two seedlings have germinated. Infestation by alien plant species is progressing at both sites and alien monkeys (Macaca fascicularis) eat unripe fruits while alien pigs (Sus scrofa) frequently rip up the ground, reducing seedling establishment. The species is thus Critically Endangered (CR B1ab(iii,v), B2ab(iii,v), C2a(i), D) according to the IUCN red list criteria (IUCN 2001). A species recovery programme is urgently required. We suggest the gradual removal of alien invasive weeds from the immediate vicinity of the plants to increase their vigour, the bagging of fruits to minimise losses to non-native monkeys and collection of ripe seeds for temporary ex-situ propagation. Seedlings obtained could then be reintroduced in nearby fenced and weeded conservation management areas. Concurrently populations should be established in arboreta. Propagation by cutting, air layering or tissue culture may be considered if sexual reproduction fails, but this should be carefully planned because an adult plant died in Brise Fer, after extensive collections were made in 1996/1997. Damage by wood-boring insects would have to be curtailed. Further surveys are also recommended.

Type

Mauritius or Réunion (Ile de France or de Bourbon), Commerson s.n. (G-DC (G00139146), n.v.).

Morphology General Habit

Small understorey erect tree, reaching 3.5 – 4 m tall, 3 – 5 cm dbh, branching at times close to the ground, then with more than one erect trunk

Morphology Branches

Branches recumbent, leaves confined to the end of branches

Morphology Leaves

Leaves with stout petiole, 3 – 17 mm long, red becoming brown with age; lamina coriaceous when dry, glabrous, dark green above, pale green below, elliptic-obovate, apex acute and ± acuminate, cuneate at the base, 8 – 24 × 2 – 9 cm, main vein ± salient in the abaxial side with minor veins ± prominent on both sides

Morphology Reproductive morphology Inflorescences

Inflorescence axillary panicle, borne among the leaves, close to apex of branch, glabrous, up to 9 cm long, 20 – 30-flowered

Morphology Reproductive morphology Flowers Calyx

Calyx glabrous, 1.5 mm long when dry, 2 mm when fresh; covered in purple gland spots, lobes triangular, 1 mm long, margin entire, non-imbricate at the base

Morphology Reproductive morphology Flowers Corolla

Corolla off-white tinged with pale pink with short purple longitudinal gland spots concentrated towards centre, glabrous, petals overlapping over 2.0 – 2.2 mm and partially fused over 1 mm, with lobe 2.5 – 4.5 mm long

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens 5, inserted at the base of the corolla lobes, anthers yellowish-brown 3.5 mm long, base of filaments neither enlarged nor fused in ring

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary purple

Morphology Reproductive morphology Flowers Pedicel

Fruiting pedicel 3.5 – 6 × 0.7 – 1.7 mm

Morphology Reproductive morphology Fruits

Fruit fleshy, pyramidal with five lobes, 1.7 – 2.1 × 1.8 – 2.3 cm, fruit changing colour from dark purple to reddish as it matures, and covered in short dark purple longitudinal gland spots Endocarp 1.2 – 1.4 × 1.5 – 1.8 cm, apex drawn into a sharp pointed tip, pyramidal, ornamented with five longitudinal prominent ridges alternating with thin irregular protruding lamellae particularly developed towards base

Morphology Reproductive morphology Seeds

Seed 1, pyramidal, smooth, brown, 8 – 9 × 7.5 – 8.5 mm.

Ecology

The species is known nowadays from the understorey of native upland forest in the region of Macchabé-Brise Fer, SW Mauritius, 20°22′50″ – 20°23′50″S; 57°26′00″ – 57°26′50″E. It was previously recorded in S Mauritius “in the humid and shaded forests near Savanna” (Bojer 1837). On 19th century maps ‘Savane’ encompassed a large forested area at the centre of which is Mt Savane, some 10 km to the SE of the Macchabé-Brise Fer region. The whole area has since been deforested except for steep mountain flanks.