Researchers discover two new species of forest plants that are native and endemic to Singapore

The two species of Hanguana - Hanguana rubinea and Hanguana triangulata - have been discovered for the first time and can only be found in Singapore

4 June 2015 - Two new species of plants - Hanguana rubinea and Hanguana triangulata - have recently been discovered in Singapore by the researchers at the Singapore Botanic Gardens, continuing the Singapore Botanic Gardens’ heritage role of studying the flora of Singapore and the region, Hanguana is the only genus in the small plant family Hanguanaceae. All species are flowering herbs which are often confined to the understorey of primary forests. The two new species, which are new to science and were discovered for the first time, are native to Singapore and can only be found here.

The Hanguana species has not been studied extensively previously. The genus Hanguana (Hanguanaceae - Commelinales) was until recently believed to be represented in Singapore by a single species, Hanguana malayana. This large helophyte (plant that grows partly submerged in water) is often seen growing by the edge of waterbodies and is occasionally used in the landscaping industry for its ornamental value.

The discovery of the Hanguana rubinea and Hanguana triangulata is unique in that there were at least 25 existing herbarium records of Hanguana at the Singapore Botanic Gardens Herbarium, some of them dating more than 100 years old. However, all previous herbarium records of this group of plants collected from Singapore were mistakenly identified as Hanguana malayana, a common misconception due to the lack of study of the genus Hanguana. With field surveys conducted at our nature reserves and areas and through the study of fresh as well as existing herbarium material, researchers from NParks have established that there are at least six species from the Hanguanaceae family in Singapore.

Characteristics critical for distinguishing Hanguana species, are often not obvious in the dried herbarium material, explaining the previous confusion. These, for example, include shape of the stigma, colour of the ripe fruits, shape of the seeds, angle at which the inflorescence branches are attached to the main axis (this is often manipulated in the specimens) or type of hairs present on young leaves (these often fall off in old leaves). The detailed study of fresh flowering and fruiting material in the current study also revealed existence of previously overlooked floral structures.   While its function is not yet fully understood, its form presents yet another potentially valuable characteristic to distinguish Hanguanas.

Said Jana Leong-Skornickova, the taxonomist behind the new discovery, “Finding any new species in heavily urbanised Singapore is almost a small miracle, in part because of our land area and also because Singapore’s flora has been so densely researched in South East Asia. Yet, the discovery of these new Hanguana species shows that tropical floras, including that of Singapore, are richer and more complex than we generally presumed. Continued effort towards documenting and fully understanding the richness of Singapore’s biodiversity is required to ensure that we correctly identify the conservation statuses of the native flora that is present on our island.”

Conservation and propagation works for Hanguana plant family

In 2014, NParks and NUS staff independently discovered another species of Hanguana, the Hanguana neglecta. This is a small primary forest herb with black berries native to Singapore and extending to Johor, Peninsular Malaysia. Considered locally Endangered, and globally Vulnerable, the specific epithet ‘neglecta’ has been chosen to reflect that this species in spite of sitting next to a path at the Bukit Timah Nature Reserve and being previously collected and studied, has been long neglected.  Currently, the only single population of this plant can be found at the Bukit Timah Nature Reserve, but through NParks’ conservation efforts, several plants have been successfully established in the ex situ collection at the Singapore Botanic Gardens.

Immediate conservation and propagation works are ongoing for the Hanguana plant family. Following the protocol for critically endangered plants, priority for re-introductions will be given to Nature Reserves and parks with suitable habitats. Upon successful establishment of the species in forest-like habitats, these species will then be considered to be re-introduced to suitable shady roadsides. There is also potential for the species to be used in the horticultural industry as ornamentals due to their foliage and long-lasting clusters of red, white or black fruits.

Singapore’s primary forests still thriving habitats for biodiversity

Singapore has balanced the needs for development with conservation of nature and biodiversity, in line with our City in a Garden vision. The discovery and rediscovery of plant species at our nature reserves and other nature areas is an indication that  Singapore still contains many thriving habitats for biodiversity. As part of NParks’ concerted efforts to conserve biodiversity in our native habitats, our professionals are engaged in systematic, long-term and coordinated surveys of our flora biodiversity. These surveys would allow us to better understand the conservation status and distribution of plants and animals and  would form the basis for sustainable management of our nature areas. This has yielded about 40 interesting finds in the last five years in primary forests and on islands in Singapore, which includes species not known to exist in Singapore, species previously thought to be extinct in Singapore and also species which are new to science.

With the discovery of the Hanguana rubinea and Hanguana triangulata, Singapore now has 3 species of endemic plants which cannot be found anywhere else in the world. These include the Zingiber singapurense, a ginger which was discovered as part of a conservation project initiated by the Singapore Botanic Gardens. Only three populations of the Zingiber singapurense has been discovered at the Central Catchment Nature Reserve, but a small number of these plants has already been successfully established in the ex situ native gingers germplasm collection at the Singapore Botanic Gardens.

Also key to conserving our native plant species is NParks’ Pasir Panjang Nursery, which is responsible for developing propagation techniques for native plant species. These native species are not found in commercial nurseries, and are grown at the Nursery for reintroduction into our parks, gardens and streetscapes. This will allow the public to appreciate our natural heritage in our urban environment.