Snow, N. & M.W. Callmander (2016). Studies in Malagasy Eugenia (Myrtaceae) — V : Eugenia quadriphylla Snow & Callm., an unusual and rare new species from the northeast. Candollea 71 : 189–193. In English, English and French abstracts.
The new species Eugenia quadriphylla N. Snow & Callm. (Myrtaceae) is described from the Makira Protected Area in northeastern Madagascar. It is easily distinguished from its congeners on the island by its thickly quadrangular branchlets and four bullate leaves per node. The species also is atypical among the majority of Eugenia species in Madagascar by virtue of its basipetally splitting calyx lobes, a character that is, however, known elsewhere in the genus. A discussion on its morphology, a line drawing, a distribution map and a preliminary assessment of its conservation status following IUCN Red List Categories and Criteria is provided for the new species.
Introduction
Recent herbarium-based studies of Eugenia L. (Myrtaceae) have effectively doubled the number of known species in Madagascar (Miller, 2000; Snow, 2008, 2011 ; Snow et al. 2012, 2015), which reflects in part extensive field studies conducted during the past approximately 30 years by many teams of botanists. A recent visit to MO by the first author revealed another new and unusual species from north-west of Masoala Peninsula in northeastern Madagascar (Fig. 1). Staff members of the Missouri Botanical Garden (MBG) collected this new species in the context of an important botanical inventory in the Makira region. This inventory was undertaken as part of an effort to identify new and important sites for conservation (Birkinshaw et al., 2009) and the Makira region was recently added to the Malagasy protected area network. This inventory led to the discovery of many new species that still need to be described (Birkinshaw et al., 2009).
As Eugenia has been better characterized in Madagascar (Snow et al. 2012, 2015) it has become clear that many species are narrowly endemic, which mirrors the situation with many other species-rich genera (see Callmander et al., 2011). The genus is decidedly concentrated in wetter areas from the northern mountain massifs and low-lying areas, south mostly along and east of the escarpment. Most of the species are known from few collections overall, and only rarely do collection labels indicate a species as being locally common. In contrast, some relatively localized areas, such as sites in the Tolagnaro area, can harbor ten or more sympatric species (Snow et al. 2012). At the current time the authors are aware of at least several more undescribed species of Eugenia from Madagascar, but in most cases are awaiting additional fertile material before describing them.
The new species described here is unique in Madagascar by having thickly four-winged branchlets, four weakly bullate leaves per node, and four leafy bracteoles subtending the flower, as well as a closed hypanthium that splits basipetally, a feature seen in other Eugenia in Madagascar (Snow, 2008), New Caledonia (Snow et al. 2016) and South America (Landrum & Kawasaki, 1997). A line drawing, a distribution map, a discussion of its morphology and a preliminary risk of extinction assessment following IUCN Red List Categories and Criteria (IUCN, 2012) is provided for the new species.
Systematics
Eugenia quadriphylla
N. Snow & Callm., spec, nova
(Fig. 2).
Typus : Madagascar. Prov. Mahajanga: Ruisseau d'Andasinanantsomanga, Amparihy, Matsoandakana, 14°55′03″S 49°25′04″E, 1206 m, 24.II.2008, Bernard, Ramiadana & Jocelyn 917 (holo-: MO-6475168!; iso-: P, TAN image seen).
Unique among species of Eugenia L. in Madagascar by the combination of its thickly four-winged branchlets, four narrowly oblong and weakly bullate leaves per node, four leafy bracteoles subtending the flower, and basipetally splitting calyx lobes.
Trees to 7 m. Bark unknown. Herbage glabrous and eglandular except where noted. Branchlets strongly quadrangular, the rounded ridges thickened and most pronounced beneath nodes. Leaves petiolate, coriaceous, 4 per node, somewhat bullate throughout, brochidodromous, elgandular, slightly discolorous, surfaces matte, evidently somewhat concentrated near tips of larger branches. Axillary colleters comprising a few to several thick ferrugineous projections. Petioles 5–7 mm, somewhat flattened or slightly sulcate adaxially. Leaf blades 12-15 × 2.8-3.8 cm, narrowly oblong, based rounded, margin slightly sinuous, apex obtuse ; adaxial venation (midvein, secondaries and tertiaries) pronounced but impressed due to weakly bullate texture ; abaxial venation protruding prominently, intramarginal vein 4-6(-8) mm from margin at midpoint of blade. Inflorescence of solitary flowers (ramiflorous or terminal) or somewhat clustered on short shoots. Peduncles rigid, 5–6 mm, tomentose. Bracteoles 4, 4-7 × c. 5 mm, very broadly ovate to broadly obovate, leafy, ascending, tomentose abaxially. Hypanthium 5–6 mm tall, cupuliform to urceolate and becoming longitudinally ribbed, tomentose to densely tomentose (trichomes whitish or somewhat ferrugineous). Calyx lobes 4, c. 5 mm long, broadly elliptic to broadly ovate, apex obtuse, adaxial surface glabrous, abaxially surface tomentose; arising from radial splitting during anthesis. Petals (only 1 seen) c. 8 × 5 mm, obovate, sparsely sericeous (trichomes dibrachiate) adaxially, glabrous abaxially. Stamens 150+, multiseriate ; anthers not seen; staminal disk glabrous. Ovary apically tomentose (surrounding base of style). Style (only 1 seen) c. 10 mm, stigma narrow. Fruits not seen (said to be green).
Etymology. — The specific epithet refers to the highly atypical situation of having four leaves arising per node.
Conservation status. — Eugenia quadriphylla is known from a single locality northwest of the Masoala Peninsula at an altitude of about 1,200 m. The montane evergreen forest at this locality is included within the newly established Makira Protected Area, but the habitat of this new species is nevertheless under threat due to human pressure, in particular unsustainable slash and burn agriculture. Recent satellite imagery from Google earth [ https://www.google.com/intl/en/earth] suggests that the collection site and the surrounding area with in a radius of approximately 1 km is forested, but from a distance of c. 2 km the area is deforested or disturbed. Despite the intensive nature of the inventory conducted by MBG (Birkinshaw et al., 2009) in the region, the new species has been collected only once, suggesting it is rare in the wild. Eugenia quadriphylla is therefore preliminary assessed as “Endangered” [EN B2(ii, iii, iv)] following IUCN Red List Categories and Criteria (IUCN, 2012).
Notes. — Several morphological traits collectively make E. quadriphylla unmistakable with the genus overall, including thickened wings on the branchlets, four weakly bullate leaves per node, the four subtending leafy bracteoles (in contrast with two bracteoles, which is much more typical for Eugenia), and an evidently united (or mostly so) calyx tube that splits basipetally during anthesis. In addition, it appears that the fruits may be longitudinally ribbed at maturity (Fig. 2), which is atypical for species in Madagascar.
The splitting calyx lobes align the species morphologically in Madagascar most closely to Eugenia ambanizanensis N. Snow (Snow, 2008), which also has this trait, the two collections of which occur in the Masoala Peninsula at a distance of c. 75 km to the southeast. However, the stamens of E. quadriphylla are arranged in a distinct ring, typical of most species of Eugenia, whereas the stamens of E. ambanizanensis are spread nearly entirely across of the inside of calyx lobes (i.e., it lacks a well defined staminal ring). Eugenia quadriphylla also differs from E. ambanizanensis in lacking the numerous thick (probably succulent when fresh) bracts subtending the flower of the latter species, and its strongly and prominently thickened quadrangular branchlets and whorled (4 per node) leaf arrangement contrasts with the terete to slightly winged and opposite leaves of E. ambanizanensis (Snow, 2008).
The basipetally splitting calyx lobes found in Eugenia quadriphylla are also suggestive of a relationship with Mascarene species initially assigned to the genus Monimiastrum Guého & Scott (Scott, 1980), which van der Merwe et al. (2005) showed was nested within Eugenia based on ITS and ETS sequences, the species of which Snow (2008) later transferred into Eugenia. Basipetally splitting calyx lobes also occur in several species of Eugenia in New Caledonia (Snow et al., 2016) and in South American species once assigned to Hexaclamys L. (Landrum & Kawasaki, 1997). Given the significant geographical distance between Madagascar/Mascarenes and South America or New Caledonia, a hypothesis of convergence of the basipetally splitting calyx lobes seems equally likely as homology (singular origin) of the trait. However, recent research (Federman et al., 2015) has corroborated previous suggestions (Schatz, 1996) of strong biogeographic affinities across the Indo-Pacific region, suggesting that the presence of splitting calyx lobes may reflect an underlying phylogenetic relationship among species bearing this trait between New Caledonia and Madagascar, despite the geographical distance separating these regions. Tracing the evolutionary and phylogenetic history of species exhibiting this character will be a useful addition to preliminary studies that focused primarily on inflorescence structure among Neotropical members of Eugenia (Mazine et al., 2014). A silica gel preserved sample of E. quadriphylla is available for DNA analysis, although it must be noted that the leaves of the type collection are heavily infested with fungal growth.
Fig. 1.
Distribution map of Eugenia quadriphylla N. Snow & Callm. (black circle) plotted on a map of forest cover in 2000 (grey) following Harper et al. (2007).
Fig. 2.
Eugenia quadriphylla N. Snow & Callm. A. Abaxial view of leaf; B. Branch and subtending (ramiflorous) inflorescence; C. Detail of flower showing longitudinally ribbed hypanthium, splitting calyx lobes, and four subtending bracteoles.
[Bernard et al. 917, MO & TAN] [Drawing: R.L. Andriamiarisoa]
Acknowledgements
We thank the curators at MO and P for ongoing assistance with studies of Malagasy Eugenia. We also thank Roger Lala Andriamiarisoa for the fine illustration and Chris Birkinshaw for sharing information on the Marika botanical inventory. Finally, we thank Pete Lowry for his careful review of the manuscript.
