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Research Article
Syzygium pyneei (Myrtaceae), a new critically endangered endemic species from Mauritius
expand article infoJames W. Byng, F. B. Vincent Florens, Claudia Baider§
† University of Aberdeen, Aberdeen and Royal Botanic Gardens, Kew, Richmond, United Kingdom
‡ University of Mauritius, Moka, Mauritius
§ Mauritius Herbarium, Reduit, Mauritius
Open Access

Abstract

A new species of Syzygium Gaertn. (Myrtaceae), S. pyneei Byng, V. Florens & Baider, is described from Mondrain Reserve on the island of Mauritius. This species is endemic to the island and differs from any other species by its combination of cauliflory, relatively large flowers, light green to cream hypanthium, light pink stamens, short thick petioles, coriaceous leaves and round, cuneate or sub-cordate to cordate leaf bases. Syzygium pyneei Byng, V. Florens & Baider is known from only two individuals from the type locality and merits the conservation status of Critically Endangered (CR C2a(i,ii); D).

Keywords

Syzygium, endemic, Mascarenes, Myrtaceae

Introduction

Syzygium Gaertn. is the largest genus in Myrtaceae with about 1200 species distributed in the Old World tropics and subtropics (WCSP 2014). Scott (1990) described fourteen species native to Mauritius after which Bosser and Florens (2000) described another new Syzygium species, S. guehoi Bosser & Florens, from the island. During recent morphological and molecular work on the genus in the African-Indian Ocean region by the first author it was noted that samples from Mondrain Reserve were quite different from any other known taxa. Therefore, the species is described here as a new species.

Taxonomic treatment

Syzygium pyneei Byng, V. Florens & Baider, sp. nov.

Figures 1, 2

Type

Mauritius, Mondrain Reserve, 30–35 m from main gate on left of path at 20°19.597'S; 57°27.241'E, 24 Nov 2006, G. D’Argent & K. Pynee MAU 25014 (holotype: MAU! [MAU 0014027; spirit MAU 0014029 fl.buds, fl.]).

Diagnosis

A cauliflorous species with relatively large flowers (> 2 cm long), light green to cream hypanthium, light pink stamens, short, thick petioles (4–8 mm long), and round, cuneate or sub-cordate to cordate leaf bases. The species could be confused with S. mauritianum but differs in the usually longer petioles, the variable leaf base and light green to cream hypanthium. Syzygium pyneei could also be confused with S. cymosum but differs from the latter species in the light green hypanthium, sepals 4–5 mm long and coriaceous leaves.

Description

Glabrous shrub to 3.5 m; bark grey to sometimes creamy-pink; branchlets terete, grey to reddish-brown. Leaves drying pale green above, light brown below; coriaceous, 10‒15 × 4.5‒9 cm, elliptic, oval-elliptic or oblong-elliptic, base round, cuneate or sub-cordate to cordate, apex acute to shortly acuminate, margin flat; 10‒18 secondary vein pairs, 3–16 mm apart, prominent on both sides, tertiary veins few, faint; inner intramarginal vein 2–4 mm from leaf margin, outer intramarginal faint, 1–2 mm from leaf margin; petiole 4‒8 mm long, robust, green when young, reddish-brown when old, 2–3 mm diameter. Inflorescences cauliflorous, ca. 6 cm long, axes terete, flowers up to 6, in clusters of 1–3; bracts and bracteoles deltoid, ca. 2 mm long, caducous. Flowers ca. 2 cm long; pseudostalk ca. 2 mm long; hypanthium 12–13 × 7–11 mm, pyriform, light green to cream; sepals 4–5 × 2–3 mm, obtusely triangular or obtuse; petals 8–9 × ca. 6 mm, orbicular; stamens 12‒15 mm long, light pink; anthers ca. 1 mm; ovules few per locule; style 7‒18 mm long. Fruits pyriform, 20 mm long × larger diameter 15.8‒19.3 mm and smaller diameter (near calyx disc) 12.5‒14 mm; colour not recorded, surface with few hairs. Seeds 1‒2, globular when 1, half-moon shape when 2; 11.2‒11.6 mm × 10.7‒12.3 × 11‒11.5 mm when globular or same height but 10 × 6 mm diameter when half-moon shape, testa bullate; not seen fresh.

Figure 1.

Vegetative characters. A and B bark C close-up of branchlet D lower leaf surface E upper leaf surface F petioles G leaf venation. (A and G Byng 83; B–F Byng 84).

Flowering and fruiting

The species was reportedly flowering for the first time in about 20 years (G. D’Argent pers. obs.) in November 2006. By 1 December 2006 most flowers (80%) were found on the ground and a few fruits were collected on 19 January 2007 after several visits monitoring the population.

Figure 2.

Floral and fruit characters. A and B Sole recorded images of flowering event C Close-up of dried inflorescence D Close-up of two fruits. (A–C D’Argent & Pynee MAU 25014; D D’Argent & K. Pynee MAU 26448; A and B courtesy of Kersley Pynee). Scale bar = 1 cm.

Distribution

This species is only known from Mauritius, and has not been recorded outside Mondrain Reserve. Only two individuals have been recorded and no seedlings have been seen.

Ecology

This species grows in a ridge forest, not fully exposed to sun and wind, at an elevation of around 520 m.

Etymology

Syzygium pyneei is named after Kersley Pynee who co-collected the type specimen and is a prominent local botanist.

Additional specimens examined

MAURITIUS, Mondrain Reserve, 10 Nov 2006, G. D’Argent & K. Pynee MAU 25013 (MAU [0014026]); 01 Dec 2006, G. D’Argent & K. Pynee MAU 26447, fl., (spirit, MAU [0014026]); 19 Jan 2007, G. D’Argent & K. Pynee MAU 26448, fr., (spirit, MAU [0014030]); 31 Mar 2011, J.W. Byng 83 (K, MAU) & 84 (E, MAU).

Discussion

Syzygium pyneei most closely resembles S. cymosum (Lam.) DC., and S. mauritianum J. Guého & A.J. Scott, sharing the cauliflorous habit, pinkish flowers and large leaves (≥ 10 cm long). S. mauritianum individuals have sessile to very short petioles (0–5 mm long), bright pinkish-red hypanthia, usually very large leaves ((10–)17–30 cm long) and strongly cordate leaf bases, in contrast to the 5–8 mm long petioles, light green to cream hypanthium and round, cuneate or sub-cordate to cordate leaf bases of S. pyneei. Scott (1990) suggested Syzygium cymosum was probably extinct on Mauritius, as no specimens had been collected for many years, but extant on La Réunion. Specimens of S. pyneei were originally thought to be related to S. cymosum when the flowering individual was first seen but S. pyneei differs by the light green to cream hypanthium (vs. light pink), sepals 4–5 mm long (vs. ca. 1 mm) and coriaceous leaves (vs. chartaceous).

In addition, molecular data (Byng unpublished data) suggests Syzygium pyneei is most closely related to S. guehoi; morphologically both species have several-flowered, cauliflorous inflorescences and are distributed on the western part of the island. However, S. pyneei has larger leaves, flowers and fruits and S. guehoi are much larger individuals, growing up to 15 m tall with conspicuous red petioles.

Conservation status

This species is currently known from only two individuals. The population at Mondrain is protected within a private reserve of around 5 ha, which has been cleared of invasive alien plants and fenced against alien deer. Outside the fenced area, which is potential habitat for further individuals, the forest is dominated by alien plants, notably Psidium cattleianum Afzel. ex Sabine, the main invader in moist to wet forests of the island and a species known to be very detrimental to native plants on Mauritius (Baider and Florens 2011; Monty et al. 2013). The reserve is adjacent to deer grazing lands to the east. Syzygium pyneei should be considered Critically Endangered (CR C2a(i,ii); D) according to the IUCN Red List Criteria (IUCN 2001).

Acknowledgements

We are grateful to the National Park and Conservation Services for permission to collect in Mauritius and also to Mr Gabriel D’Argent for his assistance in the field. The first author was funded by a University of Aberdeen BBSRC CASE studentship with Royal Botanic Gardens, Kew (2009-2013) and Plant Gateway Ltd. made funds available for its publication. We also thank two anonymous reviewers for their helpful comments.

References

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  • Monty MLF, Florens FBV, Baider C (2013) Invasive alien plants elicit reduced production of flowers and fruits in various native forest species on the tropical island of Mauritius (Mascarenes, Indian Ocean). Tropical Conservation Science 6(1): 35–49.
  • Scott AJ (1990) Myrtacées. In: Bosser J, Cadet T, Guého J, Marais W (Eds) Flore des Mascareignes: La Réunion, Maurice, Rodrigues 92. MSIRI, Port Louis, ORSTOM, Paris, Royal Botanical Gardens, London, 70 pp.
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