Noronhia macrophylla (Baker) Hong-Wa & Callm.

Hong-Wa, Cynthia, Callmander, Martin W. & Baider, Cláudia, 2014, Taxonomy and conservation of the genus Noronhia Thouars (Oleaceae) in Mauritius, Candollea 69 (2), pp. 157-163 : 159-162

Noronhia macrophylla (Baker) Hong-Wa & Callm. , comb. nova.

Ξ Olea macrophylla Baker , Fl. Mauritius: 219. 1877.

Ξ Linociera macrophylla (Baker) H. Perrier in Humbert, Fl. Madagascar Comores 166: 9. 1952 [non G. Don, Gen. Hist. 4: 53. 1837].

Ξ Chionanthus boutonii A. J. Scott in Kew Bull. 33: 570. 1979 [non C. macrophyllus (Wall. & G. Don) Blume, Mus. Bot. 1: 317. 1851].

Ξ Noronhia boutonii (A. J. Scott) Hong-Wa & Besnard in Mol. Phylogenet. Evol. 67: 375. 2013 [nom. illeg.].

Typus: MAURITIUS: s.loc., 1859, Bouton s.n. (holo-: K [ K000233207 ]!).

Observations. – Noronhia macrophylla is a rare treelet, known until recently only from the region of Mare aux Vacoas and Perrier. It can be distinguished from the other members of the genus in Mauritius by its white bark with striking black markings, its widely obovate to almost circular leaves (but more elliptic in the population at Mt. Camizard) ( Fig. 1B, 1C ), and its small white odoriferous flowers ( SCOTT & GREEN, 1981).

Conservation status. – The area of Mare aux Vacoas had a “good population” of Noronhia macrophylla (G. D’ ARGENT, pers. comm.), implying that it comprises numerous individuals, although no quantitative estimate has been made. The site was deforested in the early 1970s and almost no native vegetation remains today, except around a few small streams. Perrier, the smallest Nature Reserve of Mauritius (1.44 ha), is surrounded by eucalyptus plantations, and it has been actively managed (weeded and fenced against large hoofed mammals) since early 1960s. Due to the reserve’s small size, easy access and numerous botanical inventories, it is very unlikely that other individuals will be found at this locality. A population decline of 50% occurred at Perrier during the last 30 years, from two individuals ( VAUGHAN, 1980) to just a single tree that is about 3.5 m tall and has 4 main stems of 2.8 to 3.3 cm diameter. This tree seems healthy, although it grows on the edge of a small stream that crosses the Nature Reserve, and is thus threatened by the normal process of fluvial erosion. Material from this population has been propagated by the Mauritius Forestry Services and is also under cultivation at the Royal Botanic Gardens, Kew. Recently, a previously unknown population of N. macrophylla was located near Mt. Camizard, where an estimated 80 individuals, including seedlings, occur within a patch of forest that has been weeded and restored by a private company (BCM Mauritius) ( Fig. 2B ), which is trying to augment the population on the site, although no ripe fruits have been observed (C. GRIFFITHS, pers. comm.). The historical EOO (40 km 2) and AOO (16 km 2) are small (calculation following GEOCat version ss, see BACHAM & al., 2011). The AOO has been reduced by 50% since 1970s, and today is around 8 km 2 (reduction in EOO cannot be calculated since there are only two points). In contrast to the other members of Noronhia on Mauritius, all known plants of N. macrophylla occur within sites where alien plants have been removed. Nonetheless, N. macrophylla should be considered as “Critically Endangered” [CR A1c; B2ab(ii,iii,iv); C2a(ii); D] according to the IUCN Red List Categories and Criteria ( IUCN, 2012) due to its restricted range, loss of known localities, documented population decline (mainly by deforestation that has now ceased), and small number of reproductive individuals mostly found at a single site (<50 plants;> 99% of all reproductive plants).

Specimens examined. – MAURITIUS. Dist. Plaines Wilhems: Mare aux Vacoas, 550 m, 11.XII.1933, Vaughan 842 ( P [ P05090507 , P0509 0508 ]) ; ibid. loc., VIII.1937, Vaughan s.n. ( MAU [ MAU 0014564 ]) ; Perrier , 533 m, 17.II.1939, Vaughan V/3176 ( MAU [ MAU 0014564 ]) ; ibid. loc., 4.I.1948, Vaughan V/3176A ( MAU [ MAU 0014568 ]) ; ibid. loc., 12.I.1963, Vaughan s.n. ( MAU [ MAU 0014569 ]) ; Dist. Grand Port: Vallée de l’Est, 23.II.2011, Sevathian s.n. ( MAU [ MAU 0004 821 ]) ; Mt. Camizard (aka Vallée de l’Est), 340 m, 20°19’53’’S 57°43’31’’E, 21.VI.2014, V. Florens s.n. ( MAU [ MAU 0015248 ]).

Figures

Fig. 1. – Living plants of NoronHia Thouars on Mauritius. A. NoronHia broomeana Oliv. var. broomeana; B-C. Close-up of NoronHia macropHylla (Baker) Hong-Wa & Callm.; D. NoronHia obovata (Baker) Hong-Wa & Callm. [A: V. Florens & Baider CB 2367; B-C: Baider s.n., pers. obs.; D: Baider & V. Florens CB 2461] [Photos: A, D: V. Florens; B: C. Baider]

Fig. 2. – Distribution maps of NoronHia broomeana Oliv. var. broomeana (A), NoronHia macropHylla (Baker) Hong-Wa & Callm. (B), and NoronHia obovata (Baker) Hong-Wa & Callm. (C): Current localities (circles), historical localities (stars).