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"...the contrivances by which Orchids are fertilised, are as varied and almost as perfect as any of the most beautiful adaptations in the animal kingdom." - Charles Darwin, Fertilisation of Orchids.
Single cite
citeID 2 Darwin, C. (1877). Fertilisation of orchids: the various contrivances by which orchids are fertilized by insects. John Murray, London.
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Introduction
Few plants have the honorable status of being found only in Singapore and named after the country. One of these plants is the Singapore Nervilia, also known as Nervilia singaporensis Niissalo. In 2019, this rare and inconspicuous orchid received local media attention a year after.
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The flower of Papilionanthe Miss Joaquim (left) and its stems, leaves and aerial roots climbing on supports at the Singapore Botanic Gardens (right).
How can you support its conservation?
Provisional IUCN conservation assessment
The orchid should be classified as Critically Endangered globally in the IUCN Red list.
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The most probable extent of occurrence (EOO) is less than 100 km2 and area of occupancy is significantly below 10 km2. However, as a challenging species to find, the orchid may have been gone unnoticed at other localities in Peninsular Malaysia or Singapore. Fortunately, the species does not need pristine primary forest and survives in mature secondary forests. Due to the loss of forests near Choa Chu Kang, the only known population of the orchid is confined to a few square meters in Bukit Timah Nature Reserve. The quality of its habitat has also declined due to increased edge effects in the last century. Under the local Red list criteria and global IUCN assessment, the orchid should also be classified Critically Endangered. Information to support other threatened wildlife such as the orchid can be found here.
Orchid conservation and reintroduction programme
There are at least 200 native orchids in Singapore, more than half are nationally extinct.
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Bulbophyllum maxillare (Lindl.) Rchb.f. is one of orchids listed as Nationally Extinct being reintroduced in Singapore under the programme.
Name
Common Name: Singapore Nervilia
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Two emerging leaves and a mature fruit capsule of the orchid, growing above the forest floor leaf litter.
Etymology
Nervilia describes the prominent veins on the leaf. As the orchid was first found in Bukit Timah Nature Reserve, it was named after the type locality's country, Singapore.
Description
A size comparison size between my hand and the orchid leaves during surveys of it.
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Nervilia singaporensis with new leaves emerging in foreground, old leaves in background and a dried capsule.
Diagnosis
The developing capsule of Nervilia singaporensis after flowering recently with the bract intact.
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Clinandrial tissue surrounds the cleft anther cap dorsally for over half its length. The flower is also cleistogamous that pollinates itself by not opening fully.
Biology
General biology of genus Nervilia
Nervilia orchids are terrestrial and herbaceous and are characterized by their tubers.
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The reflective surface of Nervilia singaporensis under camera flash.
Cryptic diversity of Nervilia
An integrative morphological and phylogenetic approach was used to delimit the polyphyletic Nervilia punctata group in Southeast Asia.
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were also described using similar approaches. This approach is important for conservation of the genus, given the taxonomic difficulty in the orchid, ensuring its species diversity is not lost because of poor identification.
Phenology
In the taxonomic description of Nervilia singaporensis
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After a short flowering span, the orchid starts to develop its capsule as the perianth closes, the pollinia likely lands on its own stigma and undergoes self-fertilization.
Distribution
Nervilia singaporensis is only known from Singapore as there is unlikely any conspecific specimens from Peninsular Malaysia.
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The 163 ha intact forest Bukit Timah Nature Reserve, where the type specimen was found, highlighted in yellow, on the Singapore map. Other nearby forests are fragmented by urbanization and unlikely to contain the orchid. (Map: Google Maps)
Ecology
The orchid grows among the undergrowth vegetation of mature secondary forests in the type locality. Other plants found in the vegetation are: Ficus spp. and introduced herbs (Dieffenbachia seguine (Jacq.) Schott, Epipremnum aureum (Linden ex André) G.S.Bunting and Heliconia psittacorum L.f.). Fortunately, this orchid does not need pristine primary forest and stand a better chance of occupying other secondary forest habitats in Singapore if funding for tests are available.
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The heart shape leaves of Epipremnum aureum are very similar and difficult to discern from Nervilia singaporensis in the center of the photo.
Fungal symbiotic associations in other Nervilia orchids
Nervilia nipponica is a well-studied Japanese orchid species. However, the orchid is also a threatened species with limited distribution. Specificity to mycorrhizal fungus was suspected as a reason for its rarity.
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More importantly, such information can contribute to the orchid's conservation.
Classification
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Tracheophyta
- Class: Liliopsida
- Order: Asparagales
- Family: Orchidaceae
- Genus: Nervilia Commerson ex Gaudichaud-Beaupre
- Species: Nervilia singaporensis Niissalo
Phylogeny
Phylogenetic position of Nervilia in Orchidaceae
Nervilia belongs to the "LOWER EPIDENDROID" clade that was one of the 6000 equally parsimonious, successfully weighted rbcL trees, taken from Cameron et al. ,1999. Branch lengths (ACCTRAN optimization with equal weights) are represented by numbers above the tree branches. Nodes with strong bootstrap support values above 75% are drawn with a solid circle while those with weak bootstrap support of 50 to 74% are highlighted with open circles.
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, Nervilia is classified under the paraphyletic Lower Epidendroid orchids. The Epidendroid clade is considerably large, thus divided into "lower" and "higher" clades for convenience. It is the one of the five subfamilies of Orchidaceae, one of the largest family of plants. Within the clade, the Nervileae tribe, which Nervilia belongs to, is the sister group to the remaining tribes of Epidendroid. The phylogenetic analysis was done using parsimony from 171 taxa representing most orchids. Chloroplast rbcL exon coding sequences were used, each sequence was approximately 1330 base pairs. The species of Nervilia used in this study was Nervilia bicarinata Schltr (Voucher: Chase O-580 (K), Database accession: GBANAF074199).
Phylogenetic position of endemic orchid in Nervilia
ITS sequences from the ribosomes was utilized for this RAxML tree, outgroups are not shown.
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GenBank sequence for the type specimen for the tree above is available online. The sequence belongs to the ribosomal DNA from 18S to 26S. From the phylogenetic analysis, Nervilia singaporensis is more related to Nervilia trangensis S.W.Gale, Suddee & Duangjai from Peninsular Thailand than Nervilia punctata from Java, Indonesia. For other Nervilia species (Nervilia lanyuensis S.S.Ying, N. marmorata S.W.Gale, Suddee & Duangjai and N. infundibulifolia) that are genetically more similar to the locally endemic orchid than similar looking Nervilia punctata, their morphologies differ greatly.
Type information
The type specimen was collected on 3 December 2019 by M.A. Nissalo at Bukit Timah Nature Reserve, Singapore. Specimen ID: SING2019-1365. The holotype is a dissected inflorescence without the anther cap. It contains the fruit and stem. Holotype ID: SING0273892.
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| Single cite | ||
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Niissalo, M. A., Choo, L. M., Kurzweil, H., Yam, T. W., & Khew, G. S. (2020) A new species of Nervilia (Orchidaceae) from Singapore. Gardens Bulletin, Singapore. |
Glossary
| Terms | Definition |
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| Autogamous | an organism that fertilizes itself by fusing its own gametes |
| Cleistogamous | a self-pollination strategy where the plant's flower does not fully open for the male and female components to meet and fertilise. |
| Clinandrial | a description of the tissue found at the column of orchid before the anther cap |
| Deciduous | describes plants that shed their leaves seasonally |
| Dehisces | the action of a fruit splitting or bursting when opened |
| Dipterocarp | trees belonging to the plant family Dipterocarpoideae that dominate and characterize certain forests in South East Asia |
| Endemic | describes an organism that is native and restricted to a specific locality |
| Holotype | a type specimen where its species name and description comes from |
| Inbreeding | closely related organisms that mate with each other and often produce defective offspring |
| Phenology | the study of cyclic temporal patterns in organisms |
| Pollinia | refers to a single unit of pollen grains clumped together in a plant from one anther transferred during pollination |
| Rostellum | the projecting part of column in orchids, separating male and female components of the flower |
References
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*All photos taken by author unless stated otherwise
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