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Nymphaea alba subsp. occidentalis
(Ostenf.) Hyl., a White Water-lily

Account Summary

Native, very rare. European temperate.

July 1946; MCM & D; Carrick Lough, Dresternan Td, NW of Derrygonnelly.

Stace (1997) recognises this form with its smaller flowers and leaves as a subspecies, which occurs in unproductive lakes in W Ireland and N & W Scotland. The authors of the Typescript Flora (and the Revised Typescript Flora) listed this subspecies separately but in the latter added the comment, "This is merely a starved form of N. alba growing in a habitat deficient in nutrients."

The status of subsp. occidentalis requires further investigation, particularly since Stace goes on to point out that intermediates occur between it and subsp. alba and that the intermediates are not confined to the areas where the two forms overlap (Stace 1997).

There are just two records of the supposed subspecies in the Fermanagh Flora Database, both made by Meikle and co-workers. The second site was at Carricknagower Lake, also on the Western Plateau, recorded in July 1947.

Growth form and preferred habitats

This conspicuous rhizomatous perennial is frequently found in open water floating leaf plant communities in still, shallow-water lakes of all sizes in our area, but it also extends into adjacent reedswamp shallows. In other parts of Britain and Ireland, White Water-lily is also found to a much lesser extent in slow flowing ditches and in river backwaters, but while we have over 280 records for N. alba in Fermanagh, only once has it been listed from this type of habitat, from a drain at Cornaleck, Upper Lough Erne in 2007.

In the type of still water bodies that N. alba frequents, the bottom is typically mud, silt or peat, and it is only rarely of shingle or rock. N. alba tolerates a wide range of water chemistry and it is found in calcareous turloughs (ie vanishing lakes) and marl lakes, as well as in decidedly acidic upland lakes, often over peaty bottoms. In the Britain and Ireland, it is normally regarded as a plant of relatively shallow, still, lowland waters, but it can survive in waters up to 5 m deep (Heslop-Harrison 1955b). It reaches an altitude of 405 m at Tarn Fell in Cumberland (C.D. Preston, in: Preston et al. 2002). Colonisation of deeper waters must be entirely by means of vegetative reproduction involving rhizome fragments since seedlings cannot grow at the low light levels that prevail at depth. N. alba also occurs in waters of all levels of productivity ranging from eutrophic to oligotrophic (Preston & Croft 1997).

Although generally found in open, full sun conditions, N. alba is occasionally found in the shade of overhanging trees, or more frequently among tall emergent stems, such as those of Phragmites australis (Common Reed), where light levels may be reduced by up to 50% of full sun (Heslop-Harrison 1955b).

Under favourable growing conditions, N. alba can dominate open water in smaller lakes, the large leaves of the species completely covering the surface. Such large clonal individuals may be of very great, or indeed, indefinite age, and can measure 10 m or more in diameter. Large colonies are generally ring-like in form, the central older parts of the clone having eventually died off (Heslop-Harrison 1955b).

Recognition

In the absence of flowers, the leaves can be distinguished from those of Nuphar lutea (Yellow Water-lily), by being almost circular in outline, having the lateral veins branching at wide angles and forming a rather inconspicuous net-like web near the margin. The leaf stalks are also rounded or oval in cross section, not angular as in Nuphar (Haslam et al. 1975; N.F. Stewart, in: Rich & Jermy 1998).

Alternative growth form

The species is also known to possess a terrestrial growth form with tufts of erect leaves with rolled margins, occasionally reported in marshy habitats in several areas of Europe, eg in W Ireland on Achill Island (Praeger 1934i, paragraphs 24 & 408), by a pool south of Lough Gill near Castle Gregory (H28) and around the shores of Lough Carra (H26), where it grows on wet, calcareous marl (Heslop-Harrison 1955b). Although we have similar marl lakes in Fermanagh, to date we have not observed this rather unusual form of the species anywhere in the VC.

Fermanagh occurrence

N. alba has been recorded in 98 Fermanagh tetrads, 18.6% of those in the VC. As the tetrad distribution map indicates, it is frequent in the W, C and SE of the county, but absent from the open-water areas of our largest lakes, Upper and Lower Lough Erne. The species lacks submerged leaves and is, therefore, much less tolerant of disturbed water than Nuphar lutea (Yellow Water-lily). Thus in Fermanagh's larger lakes, and especially in the navigable channels between their many islands where water can readily become turbid through wind and wave action or as a result of boating activity, White Water-lily is absent. In these lakes, it is confined to sheltered bays and backwater shallows protected from excessive disturbance by reedbeds.

Phenology and sexual reproduction

The floating leaves are produced annually, first making their appearance at the water surface around May. The flowers, which also float, are produced from early June to August. In comparison with Nuphar lutea, the blooms open much wider, and at up to 20 cm in diameter, they are the largest individual wild flower in these islands by a wide margin. The white flowers, which are very primitive (probably dating back to the Jurassic Period), have large numbers of separate, spirally arranged parts (tepals). The flowers close at night, or when it rains, during the 4-7 days each one lasts. The female organs ripen first (ie the flowers are protogynous), with a subsequent prolonged male phase. Pollination is effected either by bees or by other insect visitors, but should this fail, selfing occurs (Heslop-Harrison 1955b; Velde 1986).

After pollination the flower is pulled about 30 cm below the water surface by contraction of the stalk. The flower rots and the fruit ripens and eventually sometime between September and early November it bursts irregularly, releasing a floating mass of mucilage and embedded seeds which resembles frog-spawn and thus attracts both water birds and fish.

Seed production and dispersal

Typical seed production averages around 500 per fruit, although the number of flowers per plant and the seed set per flower, both vary considerably with growing conditions. The seed mass mucilage consists of the transparent arils around each seed aggregated together. It entraps air, floats and enables dispersal across the water body. According to Dutch studies, this flotation may be of short duration, since any rainfall releases the entrapped air and the seeds then immediately sink (Velde 1986; Smits et al. 1989). Duck, Coot and other water birds actively eat the seed, and fish such as Common Carp will also do so, but only if they are starving. Unfortunately, at least in the case of these particular animals, ingestion does not appear to aid the plant's dispersal since, unlike Potamogeton species (Pondweeds), the seed coat is weak, allowing it to be either completely digested or killed by passage through the animal's gut. This fact does not rule out the possibility that other birds and herbivorous fish with less efficient digestion, might internally transport and excrete viable seeds (a mechanism technically known as 'endozoochorous transport'), but as far as I know there is no positive evidence of this occurring at present (Smits et al. 1989).

Transport of species between water bodies

Due to this inability of seeds to survive passage through the animal gut, aquatic plants like N. alba having a weak testa, can transfer between water systems (ie long-distance or jump-dispersal), only through external adherence of seed on the body of an animal vector. This might be achieved either through chemical stickiness, or physical projections involving some kind of burr-like seed or fruit with a spiny or a hooked surface. Our two Water-lily species, Nymphaea alba and Nuphar lutea, have no such fruit or seed properties, and thus they are not specifically adapted for external transport on animal bodies. They might still, however, adhere for a short time in mud on the feet, coat or down of an animal moving between adjacent lakes or streams.

Thus it is not completely impossible to imagine the occasional or rare stochastic longer range dispersal event occurring. Studies of very long distance bird transport of seed to remote oceanic islands has shown that the down on young fledglings may well prove significant, since seed attaches very much more readily to this type of surface than to feathers, particularly pre-flight, preened ones (Falla 1960; Carlquist 1974). In the case of Water-lily species, it is likely that external animal attachment in mud would persist only for a short space of time, perhaps a few minutes, since it has been shown that the seed is susceptible to dehydration. However, I believe that the experimental test used to examine this factor was unrealistically extreme, as it involved air drying seed in a dissector for a period of 28 days before testing their viability! (Smits et al. 1989).

Long-distance dispersal must be a repeatable, recurrent, even if random event; it is not sufficient for it to be fortuitous. Thus animals which seasonally migrate along regular routes, such as birds, are favoured vectors to carry the plant propagules (Cruden 1966).

Seed properties

Seed germination is usually successful and seedlings can sometimes be found in large numbers, but few of them survive overwinter. In water, seed may survive dormant for up to three years (Jonsell et al. 2001), although other studies suggest the seed bank is only ephemeral (Thompson et al. 1997).

Irish occurrence

In Northern Ireland, N. alba, like Nuphar lutea, is very much more frequent in the southern half of the six counties, but overall it is the less common of the two Water-lilies (NI Flora Web Page (accessed 2015) http://www.habitas.org.uk/flora/species.asp?item=2757). The overall Irish distribution shows N. alba concentrated in the N and W of the island, with a thinly scattered occurrence in the centre of the island, and a remarkable almost total absence from the SE, where it is introduced in Wexford (H12), Carlow (H13), Laois (H14) and Dublin (H21) (Praeger 1934i, paragraphs 270 & 495; Scannell & Synnott 1987).

British occurrence

The British distribution in the New Atlas fails to distinguish native populations from the many introductions that are now known to occur as a result of the fashion for garden ponds. 'Escapes' and 'deliberate releases' from such ponds are especially frequent in SE England. The New Atlas map therefore shows N. alba occurring widespread in the lowlands throughout the whole territory, but becoming much less frequent in the E and the NE as one travels northwards (C.D. Preston, in: Preston et al. 2002).

Allowing as best one can for the introduced populations, it clearly remains the case that the somewhat erratic pattern of N. alba distribution in Britain and Ireland must depend both on the current presence of suitable lowland, nearly-still-water habitats, and the long-term effectiveness of dispersal by water, and perhaps by other means, between discrete water bodies and separate catchment areas.

Clinal variation in Europe

In Europe, the genus Nymphaea is generally recognised as consisting of four or five taxa at species or subspecies level. Of these, N. alba and N. candida are the most similar, to the extent that they are regularly considered as subspecies of N. alba. While these latter two forms usually remain geographically separate, N. candida being more NE European and Asian than N. alba, intermediate forms and small areas of territorial overlap do occur between them, so that in northern Europe a 'cline' may exist, ie a gradient of gradually changing variation running between the extremes of the two forms (Heslop-Harrison 1955b).

European occurrence

Beyond Britain and Ireland, the form of the species that occurs with us (N. alba) is common and widespread in W and C Europe, and to the NW it stretches beyond 68°N in coastal Norway, although absent north of 60°N in Sweden and present, but thinning northwards in Finland and the Baltic States (Jonsell et al. 2001). In southern Europe, the distribution thins, both in the Iberian peninsula and towards the Mediterranean, where there are a number of extinctions, eg on Sicily and the southern end of Sardinia. This thinning and local extinction pattern is also repeated towards E Europe and SW Asia (Jalas & Suominen 1989, Map 1509).

World occurrence

The southern limit of N. alba is reached in Algeria, and the SE extremity in Kishmir and the Himalaya (Heslop-Harrison 1955b; Hultén & Fries 1986, Map 812).

Fossil history

The fossil seed and pollen record of N. alba extends back to the Cromer Forest Bed interglacial series and it appears in all subsequent warm periods including the present Flandrian/Littletonian in Britain and Ireland. Indeed, the species is capable of surviving considerable frost, being present within the Arctic Circle at present, and a continuous fossil record runs back to the middle and late stages of the last major Ice Age, called the 'Weichselian' in Britain and the 'Midlandian' in Ireland. It is possible, therefore, that N. alba might have survived in situ the British Isles during much colder phases than the present, perhaps living quite close to the edge of the ice sheets under periglacial conditions (Godwin 1975).

Toxicity and uses

All parts of the plant, except the seeds, contain the alkaloid nupharine, the amount present varying with the season (Heslop-Harrison 1955b). The rhizome and leaves have a history of use in herbal medicine, as in addition they contain tannin, gallic acid, resin and mucilage. Grieve (1931, p. 484) details the plant's use in cases of dysentery, diarrhoea, gonorrhoea and leucorrhoea. The leaves and 'roots' were also used to poultice boils, tumours, ulcers and inflamed skin, and an infusion was gargled for mouth and throat ulcers.

Other folk uses include the starchy rhizome as a food in parts of Finland and Russia, and the same plant organ was a source of purple-black dye for wool and yarn in the Inner Hebrides (Heslop-Harrison 1955b; Vickery 1995).

Names

The genus name 'Nymphaea' is from the Greek name 'Nymphe' given by Theophrastus to an unknown water plant after one of the three half-divine water nymphs who in mythology inhabited seas, streams and woods (Gilbert-Carter 1964; Chicheley Plowden 1972). The Latin specific epithet 'alba', means white.

There are at least 16 local English common names listed in total between Britten & Holland (1886) and Grigson (1987). Some names are poetic and very evocative of the beautiful floating flower, eg 'Lady of the lake' and 'Swan amongst the flowers'. In his famous evocation of Cotswold village life, Cider with Rosie, the author Laurie Lee (1959) spoke of the white flowers, "... they poured from their leaves like candle-fat, ran molten and then cooled on the water."

A high proportion of the English common names refer either to 'water', eg 'Water Bells', 'Water Blob', 'Water Socks', 'Water Rose', or to 'floating', for instance, 'Floating Dock', of which 'Flatter Dock' is probably just a variant. References to the conspicuous broad leaves of the plant are only to be expected, and comparison with 'dock', as already mentioned, eg 'Can-dock', 'Can-leaves'. 'Can' is a reference to the carafe or jug-like shape of the fruit capsule (Grigson 1987). 'Bobbins' is a name applied to both Nymphaea alba and Nuphar lutea, being a further shape comparison of the globular fruit to a lace or weaving bobbin. The name 'Cambie-leaf' is a curious one of northern Scottish origin, applied there again to both of the common water lilies. I would welcome any explanation of the derivation. Yet another name applied to both species in early herbals is 'Nenuphar', which Grigson (1987) reports came down via Mediaeval Latin from the Sanskrit 'nilotpala', the name for the Blue Lotus of India, Nymphaea stellata. By comparison, Caltha palustris (Marsh Marigold) is 'Petie nenufar' (ie 'Petty nenufar'), in Turner's The Names of Herbes, 1548 (Watts 2000).

Threats

None, except perhaps undue water turbidity resulting from disturbance.