On the Mauritian origin of Badula ovalifolia (Myrsinaceae), hitherto believed extinct, with complementary description
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- Florens, F.B.V., Baider, C. & Bosser, J. Kew Bull (2008) 63: 481. doi:10.1007/s12225-008-9069-z
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The origin of Badula ovalifolia A. DC. (Myrsinaceae) is discussed and, on the evidence of recently collected specimens, we conclude that it is endemic to Mauritius and not to Reunion as previously recorded. The first description of the whole tree, fruit and seed and habitat and ecology are given. Conservation status is assessed using the IUCN Red List Criteria with suggestions for a species recovery programme.
In the Mascarenes, Myrsinaceae is represented by two native genera, Embelia Burm. f. (three species) and Badula Juss. (14 species). All Mascarene Badula species apart from B. crassa A. DC. are said to be endemic to one or other of the Mascarene Islands (Coode 1981).
When the Flore des Mascareignes volume on Myrsinaceae was published, Badula ovalifolia A. DC. was known only from the type in Geneva (G-DC) and two sheets in Paris (P, 1821 — det. Carl Mez 1901), all believed to be from the same collection (Coode 1981). Uncertainty existed about its origin with the type annotated ‘Mauritius’ but the two specimens in Paris were initially annotated “Reunion” and “Mauritius” respectively, with the addition of “or Reunion” to the latter sample. Since the species seemed closely related to the Reunion endemic B. barthesia A. DC., Coode (1981) considered a Reunion origin more likely; furthermore Cordemoy, who worked extensively on Reunion, and gave a brief description of the species, noted it to be quite rare and occurring in forests (Cordemoy 1895: 444). However, Coode (loc. cit) examined a sample identified by Cordemoy which, although sterile, he determined as B. barthesia A. DC. and not B. ovalifolia. Currently, the plant is treated as a Reunion species, but has not been seen there since Cordemoy’s putative record (C. Lavergne, pers. comm. 2006) and is believed extinct (Walter & Gillet 1998).
However, Bojer (1837) had previously listed Badula ovalifolia among the Badula species for Mauritius, although Coode (1981) pointed out that there could be no certainty that the synonymies of Bojer’s Badula were correctly done, since several samples were lost or sent to Geneva without indication of origin.
In 2005, we collected samples in Mauritian forests that matched in all respects Coode’s albeit brief description for Badula ovalifolia. This, along with the total absence of a positive record of the species on Reunion and its early record as a Mauritian species (Bojer 1837), reinforces our belief that B. ovalifolia is in fact endemic to Mauritius and has previously been given as a Reunion species by error.
It seems that the peculiar shape of the fruits of Badula ovalifolia, which were never described, has confused previous workers. Coode examined a sample with detached fruits that he believed was B. multiflora A. DC. in which he added: “I do not think the fruits have anything to do with the leaves.” (Owadally s.n. MAU). Page & D’Argent (1997), collected flowering and fruiting B. ovalifolia in Brise Fer forest but could not identify it and believed it to be a new Badula species.
We collected a sample with flowers from a plant in Macchabé, SW Mauritius, in April 2005 (MAU 24312) and another with fruits from the same plant a month later (MAU 24313). Coode’s description was based on an incomplete sample with only damaged flowers available to him. Here we provide an emended description of the species.
Myrsine ovalifolia (A. DC.) D. Dietr. (1839: 619).
Icacorea ovalifolia (A. DC.) Cordem. (1895: 444), only concerning the type.
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. Branches recumbent, leaves confined to the end of branches. 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. Inflorescence axillary panicle, borne among the leaves, close to apex of branch, glabrous, up to 9 cm long, 20 – 30-flowered. 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. 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. 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. Ovary purple. Fruiting pedicel 3.5 – 6 × 0.7 – 1.7 mm. 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. Seed 1, pyramidal, smooth, brown, 8 – 9 × 7.5 – 8.5 mm.
Material Examined. ‘Reunion (Ile Bourbon)’: Commerson, s.n. (P00540823); ‘Mauritius or Reunion (Ile De France Ou Bourbon)’: Commerson, s.n. (P00540824); Mauritius: Macchabé, fr. 10 Jan. 1973, Owadally s.n. (MAU); Brise Fer, fr. 13 Aug. 1996. Page 204 & D’Argent (MAU); Brise Fer, fr., 26 Aug. 1996, D. Florens & D’Argent s.n. (MAU); Brise Fer, fl., 29 Jan. 1997, Page 235 (MAU); Macchabé, fl., 9 April 2005, V. Florens & Baider s.n. (MAU); Macchabé, fr., 23 May 2005, V. Florens & Baider s.n. (MAU).
Habitat. 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.
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.
Ecology and Conservation Status. 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. Also 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.
We are grateful to the National Parks and Conservation Services for granting permission for research to be conducted in the Black River Gorges National Park. Part of the survey that led to the find was made possible with funding from the British Ecological Society through its Overseas Bursary Scheme of 2003. Two anonymous reviewers helped to improve the text.