Silently and surreptitiously, a brash but beautiful alien invader has spread its tentacles to most of the water bodies in the country as well as official documentation, flaunting its vivid violet blooms to outshine its humble native cousins, the manel and the olu.
Let alone invading the country’s water bodies it has also got itself hybridized (crossed) with the native manel which is a day-bloomer which could lead to serious consequences including the extinction of the native, the Sunday Times learns, with this being the first record of an invading exotic-native hybridization in Sri Lanka.
The native under threat is manel (N. nouchali Burm. f.) especially the National Flower, Nil-manel (N. nouchali -- N. stellata was the scientific name at the time it was declared in 1986, but now this is the correct name).
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| The imposter |
The invader is also a threat to olu (N. pubescens Willd.), a night-bloomer, taking over its habitat and making it lose space in the country’s water-bodies, it is understood.
This accused in the dock of a major study that has been carried out across the country, the violet invader, though part of the family of water lilies (Nymphaea) is an ornamental aquatic species believed to have been introduced a long time back and spread rapidly in water bodies to become naturalized, the Sunday Times learns.
To add insult to injury to the natives, not only has the violet-flowered Nymphaea led to the shrinking of pure N. nouchali populations, it has also been erroneously identified as the native in both scientific and non-scientific literature, it is understood.
This error has been carried to such an extreme that after Nil manel was declared the National Flower, the picture depicting it is that of the violet invader, explains Prof. Deepthi Yakandawala of the Peradeniya University, the crusader fighting a lone battle to give a place in the sun to the Nil manel. The Sunday Times in an exclusive story titled, ‘The great pretender’ on November 7, 2010 highlighted the mistaken identity issue with evidence from Prof. Yakandawala.
In a six-year quest, Prof. Yakandawala, Prof. of Botany, Department of Botany, Peradeniya, has trekked to many a tank and water-hole to uncover the imposter-invader. Her labours have now blossomed as a research paper that has been submitted for publication to name the violet-flowered Nymphaea. By her side supporting her with all her work and acting as collaborator is husband Dr. Kapila Yakandawala of the Wayamba University.
The violet invader is a hybrid, stresses Prof. Yakandawala explaining that based on present observations, one of its parents is N. micrantha Gill. & Perr and the other possibly is either N. capensis Thunb or N. caerulea Savigny. Prof. Yakandawala whose business is plants speaks with authority, for her “preliminary investigation” to identify and estimate the extent of the spread of the alien exotic covered more than 120 water bodies in all three major climatic zones – wet, intermediate and dry.
A hybrid occurs when two different plant varieties are crossed to produce the valued attributes of each variety. Hybrids are developed for disease-resistance, size, flowering, colour, taste and any reason a plant might be considered special. In the natural environment, when two closely-related species are present, natural hybridization could invariably occur, it is learnt. (See box)
The violet-flowered Nymphaea occurs in abundance, says Prof. Yakandwala who has waded and sloshed through mud not only in large, medium and small tanks and pools but also climbed into ditches to peer at water lilies during her study, adding that it has also extended its territory to larger tanks which are habitats of other aquatic plants. The large leaves floating on the surface, cuts down a fair percentage of the light that penetrates into the water.
The ability of this invader to conquer the water-bodies could be attributed to its hybrid origin, according to this plant expert, who points out that it is also possible that several introductions were made of this Nymphaea to the country at different stages, because of its ornamental value, paving the way for it to mix, hybridize and initiate the invasiveness. “The most suitable violet-flowered hybrid has got established, extending its territory.”
With the erroneous identification of the violet-flowered Nymphaea species as N. nouchali (Nil manel), the National Flower, they play a prominent role in social, cultural and religious events and could very well have resulted in people being instrumental in its spread, it is understood.
Pinpointing how this invader spreads its tentacles easily, Prof. Yakandawala says the plant does not produce viable seeds but reproduces by vivipary (developing a new plant while still attached to the parent plant), which is an effective method of propagation and dispersal.
Virtually almost all the mature leaves are capable of producing a plantlet at the junction where the petiole meets the leaf lamina.
The disclosures with regard to the flawed identity of the Nymphaea with violet flowers, its hybrid origin and the hybridization with native N. nouchali has opened up new avenues for major research on alien invasions into Sri Lanka, she says, adding that these findings provide an excellent opportunity to initiate studies locally on this novel area of hybridization between natives and invasive alien species.
Although thrilled about her findings, Prof. Yakandawala has one major regret that the violet invader continues to be portrayed as the National Flower.
“Even after all the hard and meticulous work, the imposter reigns,” she adds.
| Natives under threat |
Dealing at length with the dangers being posed by the invader where hybridization is creating populations of Nymphaea with intermediate characters, Prof. Yakandawala points out that scientists engaged in research on a global scale have attributed invasivness to the phenomenon of hybridization.
Plants that result from hybridization between natives and exotics could result in a hybrid with invasiveness, such research has unfolded, this botanist says, stressing that this is something Sri Lanka needs to focus on.
Hybridization of invasive aliens with native flora is currently identified as a major threat which could lead to the extinction of the native flora, she reiterates, giving evidence in the form of work done by researchers worldwide that biota (plants and animals) of islands should receive special attention as this may be a significant threat to rare species, thereby diluting the native gene pool to the point of extinction.
Delving into the work of many other scientists who have engaged in bringing to the fore the importance of plant systematics (the identification of plants), Prof. Yakandawala says it is important to identify the hybrid taxa as the base for studying the invasion ecology of congeneric species.
The basis for such a study lies in the identification of the parent plants. The present incorrect identification of the violet-flowered Nymphae a species as native N. nouchali is a classic example where the former species is treated as a native as well as the National Flower, overlooking the invasiveness, she says.
Some of the worldwide examples are cordgrass, where hybrids between Spartina foliosa (native California cordgrass) and S. alterniflora (alien Atlantic smooth cordgrass) originated in the tidal salt marshes of San Francisco Bay following the introduction of the Atlantic smooth cordgrass into the range of the native. Although earlier, it was assumed that the cordgrass invader was Atlantic smooth cordgrass, later work using molecular markers suggested that the plants invading the new sites were hybrids and pure Atlantic smooth cordgrass plants were common only in sites where they were initially planted.
From studies done in other countries on island plants, Prof. Yakandawala cites the examples of common butterwort (Pinguicula vulgaris), which is locally rare in the British Isles and Canary madrona (Arbutus canariensis) and Hawaiian ebony (Gossypium tomentosum) which are endemic to the Canary and Hawaiian Islands, respectively.
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