“The clearest way into the Universe is through a forest wilderness.” – John Muir
Figure 1 (Left): Underside of a Syzygium grande crown at the Singapore Botanic Gardens. (Photograph by Tan WA Lorraine)
Introduction
Table of Contents
Syzygium grande can be found throughout the tropical Asia in a large variety of habitats [2,3]. This includes coastal forest, where it can be commonly found in Singapore. Syzygium grande is also cultivated in Singapore as a roadside ornamental tree [3]. The common name is Sea Apple, with other names such as Jambu Laut or Jambu Air Laut [4]. Capable of growing up to 30 m in height, one towering individual in Sentosa has also been awarded the Heritage Tree status.
Although it is Common in Singapore, S. grande is a species that is part of the natural heritage in Singapore [5]. This page aims to encourage an appreciation for the biology, value, and taxonomic history of S. grande as a part of our native flora.
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Biology
Distribution
Native Distribution:Thailand, India, Sri Lanka, Burma, Indo-China, Malaysia, Singapore, Borneo [2]
Worldwide distribution:
Syzygium grande is an introduced species in the New World Tropics but has one native species in Hawaii [6,7]. According to the IUCN Red List, S. grande has been listed as one of its accepted synonyms, Syzygium firmum. Syzygium firmum is considered Vulnerable, but the range description only includes Sri Lanka and needs updating [8].
Description
| Large tree up to 30 m tall and 80 cm in diameter. Dense crown, dark and glossy with oblong shape [3]. |
 Cultivated S. grande along a road side. |
| The flowers are up to 3 cm across, white, and sessile [2]. Each flower has many stamens about 10 mm long and one 9–15.4 mm style exceeding them. Up to 14 cm long inflorescences can be found at the base of a leaf stalk, or at the ends of its branches [3]. The flowers are also very strongly fragrant [4]. |
 Flowers of S. grande and the downturned leaves. Close-up of a flower by Photos of NUS Toddycats, ICCS, and LKCNHM on Flickr |
| It produces fleshy fruits that are ellipsoid, about 4 cm long and 3 cm wide that are green when ripe [3,4]. Each fruit has a prominent 6mm diameter apical calyx rim and one seed [3]. |
 Ripe fruits of S. grande. |
| It has simple, opposite, stalked leaves that are broadly elliptic, about 16 cm long and 9 cm wide [2,3]. The leaves are darker green above, lighter green below, and each has a down-turned leaf tip. Two intramarginal veins run parallel to the leaf margin, with 9–16 pairs of side veins [2]. |
 Senescent leaf showing the distinct intramarginal vein, edited from uforest.org Leaves of a seedling showing the leaf arrangement. (Photograph by Tan WA Lorraine) |
| The bark is pale-grey to pink-brown, becoming cracked and flaky with age [3]. The base of the trunk is fluted but are not truly buttressed [4]. |
 Trunk of an individual from the Singapore Botanic Gardens. (Photograph by Tan WA Lorraine) |
Ecology
Syzygium grande can be found in habitats which include: bamboo forest, savannah, edges of evergreen forest and coastal forest [2,3]. It is a perennial which grows relatively quickly and generally flowers and fruits from March to May in Singapore, with exceptions [4]. As the seeds are common and germinate readily, the species helps with natural regeneration [9].The fruits are eaten by bats which helps with their dispersal [9]. Syzygium grande is also the caterpillar host plant for butterflies species such as the Centaur Oakblue (Arhopala centaurus nakula) and the Plain Plushblue (Flos apidanus saturatus) [10,11].
With birds, a Thai study in Khao Yai National Park found that although Syzygium spp. (as Eugenia) trees represented only 3% of all large trees in 302 sample plots, they managed to garner 26% of the hornbill nests recorded [12]. Knowing the range and habit of S. grande, S. grande could be included in this observation and be beneficial to the local species of hornbill in Singapore.
Another bird association that has been observed is with Red-breasted Parakeets (Psittacula alexandri) in Singapore, where they have been observed to eat the flowers of S. grande.
Uses
The trunk is used as timber, a medium hard wood known as ‘Kelat’ [9]. It is also an ornamental tree that was planted as a roadside tree in Singapore to act as fire breaks from lalang fires [3]. Recently, to reduce the risk of branch falls [13], roadside S. grande trees have been replaced by a shorter species (up to 20 m) Tristaniopsis whiteana, or River Tristania.More information on the ornamental uses and cultivation of S. grande can be found here.
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Taxonomy
Classification
- Kingdom: Plantae
- Phylum: Tracheophyta
- Class: Magnoliopsida
- Order: Myrtales
- Family: Myrtaceae
- Genus: Syzygium
- Species: Syzygium grande
Origin of Name
Greek syzygos, joined, referring to the paired leaves of this genus; Latin grandis, great, referring to the large leaf and flower bud [3].Name and Type
Syzygium grande (Wight) Walp. was originally described as Eugenia grandis Wight (1841) [14] as seen in Figure 3.
Figure 3: Description of Eugenia grandis Wight. Taken from the Biodiversity Heritage Library.
There was no specific holotype assigned in the original description, with the given information only listed as “Mergui—Griffith Silhet”. As such, a lectotype was designated by Byng et al. [15] with the details as follows: “—BURMA [Myanmar]. Mergui, Griffith s.n. (K! [barcode K000821429]; isolectotype P! [barcode P05208756])”.
The accepted name was given by Walpers in 1843 [16].
Synonyms
The synonyms were taken from The Plant List ver 1.1:- Eugenia cymosa Roxb. (Illegitimate)
- Eugenia grandis Wight
- Eugenia laosensis Gagnep.
- Eugenia laosensis var. quocensis Gagnep.
- Eugenia montana Wight (Illegitimate)
- Jambosa firma Blume
- Jambosa grandis (Wight) Blume
- Syzygium firmum (Blume) Thwaites
- Syzygium gadgilii M.R.Almeida (Illegitimate)
- Syzygium grande var. parviflorum Chantaran. & J.Parn.
- Syzygium laosense (Gagnep.) Merr. & L.M.Perry
- Syzygium laosense var. quocense (Gagnep.) H.T.Chang & R.H.Miao
- Syzygium megalophyllum Merr. & L.M.Perry
- Syzygium montanum Thwaites & Hook.f.
- Syzygium tamilnadensis Rathakr. & V.Chithra (Illegitimate)
Roxburgh described the species in 1832 as Eugenia cymosa, before Wight [17]. This description was deemed illegitimate because the name Eugenia cymosa was already used by Lamarck in 1789 for Syzygium cymosum (Lam.) DC. [18]. This is why Wight’s description contains Roxburgh’s name for the species as Eugenia cymosa non Lam..
Eugenia-Syzygium split
Syzygium Gaertn. [19] is the largest genus in the Myrtaceae and has about 1200 species of evergreen trees and shrubs in the Old World tropics and subtropics [3]. Separating species has been difficult due to few diagnostic characteristics and great variability [20]. There has also been much confusion because many Syzygium species were originally described under the Neotropical genus Eugenia.Merrill and Perry were the first to provide prominent modern research for the taxonomic revisions of Eugenia L. and Syzygium Gaertn. [21]. It was only more than 30 years later that this argument gained more ground, when Schmid provided strong floristic evidence to separate the two genera [22]. Even then, there was practical difficulty in telling apart the leaves, making the trend unpopular [4]. In molecular data, Gadek et al. were the first to use matK data to show the separation of the Asian Syzygium from the Neotropical Eugenia [23]. Their analysis showed that Syzygium is separate from the Myrtoidae clade which Eugenia belongs to, with bootstrap certainty of 52%. This, coupled with molecular and morphological data from many other studies, has led to the conclusion that the separation is fact [7].
As molecular analyses grew in frequency, Soh and Parnell were able to focus on Syzygium in greater detail [24]. In their study, they investigated the phylogenetic relationships of subgenera within the Syzygium genus. Through analysing DNA sequences (ETS and ITS) and leaf morphology, they were able to generate a strict consensus tree from eight of the Most Parsimonious Trees (MPTs) (Figure 4). This tree has higher bootstrap support than the analysis of the DNA evidence alone. However, the exact relationships between S. grande and the closely related species are still unclear due to the polytomy.
Syzygium cumini is also a tree that can be found in tropical Asia, but it is an exotic that has been introduced in Singapore [25]. The other species have distributions restricted to mainland Southeast Asia [26].
Figure 4: Strict consensus tree of eight MPTs retrieved from the combined analysis of ETS, ITS and morphological data. Bootstrap values >50% are indicated above the branches. Bayesian posterior probabilities are indicated below the branches. Dashed line indicates alternative branching retrieved from Bayesian analysis. Adapted from Soh and Parnell [24].
Future Work
For future work in the Syzygium genus, Parnell et al. [7] predicts that there will be a lot of logistical difficulty. There is currently insufficient data for such a species rich, widespread and poorly known genus. Molecular data has been limited on the reliability of genes and phylogenetically important morphological data (such as leaf anatomy [24]) are still being discovered. These limit understanding what drives diversification in Syzygium and the different breeding mechanisms of the species.Their work also showed that it may be operationally unfeasible to adhere strictly to the concept of monophyly [7]. Variation patterns of Syzygium in Southeast Asia differ from Australasia partly due to different breeding systems, making applying a uniform species concept difficult. From this arises the debate among taxonomists for what is "sufficient mass" to justify the possibility of splitting the very large Syzygium into smaller genera. As such, there is a lot of potential in looking into the genus and S. grande would be part of the scrutiny in years to come.
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References
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