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Species in the spotlight

A small wonder of nature saved from extinction

Nymphaea thermarum, listed as Extinct in the Wild, is unique. It is the smallest water lily in the

world, endemic to one single site in Rwanda, and has not been recorded elsewhere, despite extensive searches. The intriguing story about this scientifi c rarity seems more like a drama screenplay than a true scientifi c achievement.

It was discovered in 1987 by Professor Dr. Eberhard Fischer at Mashyzuza near Nyakabuye in Rwanda. Its specifi c habitat requirements seem improbable; it is known only from a muddy site fl ooded by a series of hot springs that fl ow at 80ºC, where the waters have cooled to approximately 24-26ºC (Fischer 1993).

A few specimens were airlifted from its only known location soon after its discovery and were kept at Bonn University Botanic Gardens, where botanists were hoping to propagate the species. All attempts failed. While growing mature specimens seemed to be relatively easy and seeds easily germinated, the seedlings were impossible to grow to maturity and died shortly after they germinated. The urgency for understanding its growing requirements became increasingly evident as repeated searches in numerous hot springs across central Africa failed to fi nd another single population (Fischer, pers. comm. 2010). In 2008, a pump was installed in the only hot spring where N. thermarum used to grow, sequestering the water before it reached the surface. The whole habitat dried out in the sun, and

the last 50 specimens growing in the wild died. Probably millions of years of evolution in stable conditions were wiped out in one single human action.

In 2009, Carlos Magdalena, a senior horticulturist from the Royal Botanic Gardens, Kew in London, unveiled the secret. While the seeds of all other Nymphaea species are traditionally grown deep, submerged in water, this species was again different. Growing the seedlings in pots fi lled with loam totally damp but so shallow that the surface of the compost (and therefore the seedlings) was exposed to the air, was the simple change that made all the difference and was all that was needed to save the species. Once its ex-situ growing requirements were met and fully understood the species was easy to propagate. Hundreds of plants are currently being grown at the Royal

Botanic Gardens, Kew, while not a single one has survived in the wild.

If Professor Fischer had missed the ”unusual” little plants while he was looking at the area, the species would never have been discovered and its extinction would have gone unnoticed. If Fischer had considered that his duty as a botanist ended just as he described the species instead of also trying to fi gure out the conservation status, then the plants would have reached Germany only as dried (and therefore dead) specimens and there would have been no material from which to propagate. In addition, had the Bonn Botanic Gardens failed to provide facilities and horticultural skills over a long period of time, it would have also been lost forever. If Bonn had decided to keep these little gems for themselves instead of sharing them with other institutions, then the mystery about how to propagate this species may have never been solved at Kew.

All the above highlights the importance of knowing what species we have, where they grow and which ones are really in peril. Once those are identifi ed, we can spare the resources and the skilled staff able achieve the goal of keeping them going. This particular species has a huge potential for a reintroduction programme, and its story is fascinating enough to raise awareness about the wonders and singularities of nature and, sometimes, its compelling fragility. N. thermarum illustrates a success story for which its last chapter is yet to be written.

Magdalena, C¹ and Juffe Bignoli, D²

¹ Royal Botanic Gardens, Kew. ² Freshwater Biodiversity Unit, IUCN.

The minute fl ower of Nympheae

thermarum, listed as Extinct in the

Wild. © C MAGDALENA

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Species in the spotlight

Sailing fl owers

Lagarosiphon is a genus with nine species that are confi ned to Africa and Madagascar. One species (Lagarosiphon

major) has become naturalized in Europe and New Zealand. It has been in Europe since, at least, 1910. Occasionally it fl ares up in pools and lakes where it may interfere with sport fi shing. In New Zealand it has become a serious pest; large populations can choke dams and rivers, interfering with the generation of electricity and irrigation. It has, therefore, been gazetted as a class B noxious plant. Following this, it was declared to be a pest in Australia (one can be fi ned up to AUS 80,000 for introducing it to Queensland) and also in the USA, despite the fact that it is not naturalized in either of these countries. It is probably this

information that led to the species being declared a noxious weed in South Africa although it is in fact, endemic to southern Africa, confi ned to an area extending from southern Zimbabwe to South Africa, where it leads a modest and blameless existence!

Although most species of Lagarosiphon are common, they have not merited presentable vernacular names – they are just called oxygen weeds or babergrass. Even the Latin name, which is in fact Greek, is boringly technical: Lagarosiphon is derived from the Greek words lagarós, meaning thin or weak, and siphon, tube - which refers to the long tube joining the ”fl ower” with the ovary. From a distance the plants do not look exciting, and perhaps deserve their lack of interesting common

names. On top of it all, they are not particularly good at producing oxygen.

When they fl ower a real wonder takes place. The fl ower buds of the male plants become detached from the mother plant; they are liberated under water and come to fl oat on the surface of the water. Then, relatively quickly and in front of your eyes, they open. At fi rst the sepals and petals bend back on themselves. Their outer surfaces are wettable, so they stick to the water surface, which stabilizes the fl ower so that it cannot capsize. The inside parts of the fl ower are unwettable and remain dry. Three fertile stamens then stretch horizontally, parallel to the water surface. Three sterile stamens become feather-like and elongate, eventually reaching upwards to form a sail. The male fl ower is a perfectly engineered tiny sailing boat that skims over the water surface with the slightest breeze. This is something unique in the plant kingdom

The stamen is also very special. Only one pollen mother cell from each of the four pollen sacs divides. Each stamen thus develops only 16 pollen grains. This is the minimum possible number of pollen grains for a complete anther. The anthers take a vertical position at right angles to the stamen fi lament. The pollen grains are abnormally large; they are presented on the outer surface of the anther, just in the right position to deposit their grains on the upright stigmas of the female fl owers, which they hit while skimming over the water surface.

Just because Lagarosiphon major leads a modest life in southern Africa today, it does not mean that it must stay so. Perhaps major alterations to the environment could encourage its ability for very fast growth, and it could become a serious threat.

Cook, C.D.K

Lagarosiphon major fl owers. © C.D.K. COOK

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Palmiet (Prionium serratum) is the only African representative of the family Thurniaceae, but up to the

recent past it has been allocated either to the family Juncaceae or given its own family Prioniaceae. Even though palmiet in itself is not a threatened species (listed as Least Concern), the unique ecosystems that it forms are becoming increasingly rare.

Palmiet is a special type of plant in that it is an ecosystem engineer. It creates wetlands by growing in dense stands that block the fl ow of rivers. These wetlands are subsequently colonized by many other plant species that would otherwise not fi nd suitable habitats. In that sense, P. serratum forms the basal structure for a complete ecosystem, and is responsible for creating the most extensive peatlands of the Cape Floristic Region. Pools that come into existence when river fl ows are blocked by Palmiet also provide valuable habitats for animals such as fi sh. For example, the Clanwilliam Yellowfi sh (Labeobarbus capensis) is a threatened species (Vulnerable) endemic to the Olifants River System on the West Coast of South Africa, where deep permanent pools with good cover provided by palmiet beds are important refuges for the species in seasonal rivers during the hot dry summers.

Palmiet’s distribution is limited to Table Mountain Sandstone (TMS). It only grows on this extremely nutrient-poor substrate so does not occur away from the Cape Mountains. The nutrient-poor conditions in which palmiet grows are in sharp contrast with the luxurious growth form that it exhibits. A single ramet of the plant consists of a light woody stem covered in old leaf sheaths, which

protect the living tissues against fi re. On top of the stem it carries a crown of stiff greyish serrated leaves with sharp edges, making it diffi cult to move around in an area dominated by palmiet. Underground, the palmiet plant has a dense network of fi brous roots that extend far deeper than any other wetland plant occurring in its habitat, sometimes reaching fi ve metres deep. This root network extends deep into the peatland and, since palmiet grows in dense, widespread, stands, it is assumed that this underlying fi brous root system has a considerable impact on ecosystem functioning.

Palmiet occurs in two very distinct habitats: mountain streams and peatlands. In the fi rst habitat, small plants of palmiet can be found lining Cape mountain streams or even headwater seepages. The second habitat is created entirely by autogenous succession (where the stimulus for change is internal) of the palmiet plants themselves. In the foothill zone of rivers the species can form dense stands that slow down the water fl ow. Since palmiet is able to grow in fl owing water it can

choke the river leading to inundation of large areas of the valley. In this situation, peat will start to form and the palmiet itself will then be able to further expand the area that it occupies. In these situations, palmiet will create a habitat for many other riverine and wetland species that grow between the palmiet plants.

The species occurs in two disjunct populations on two different strata of quartizitic sandstone. The Table Mountain group sandstones are found in the Western Cape Mountains. Here Palmiet occurs together with plants such as Wachendorfi a thyrsifl ora, Cliffortia strobilifera and Calopsis paniculata. On the Natal Group sandstones, extending from the Eastern Cape into southern KwaZulu-Natal, palmiet is also found, often occurring together with Pondoland endemic species such as Leucadendron

pondoense and Syzygium pondoense. The palmiet here has slightly narrower leaves with less of the greyish shine as seen in the Table Mountain populations, so it has been suggested that this may represent a second species. The name ”Palmiet Valley” that can be found on maps of the city of Durban in southern KwaZulu-Natal, suggests that the distribution range of this second form of palmiet historically must have extended further north than it does today.

Most farmers in the area have a paradoxical relationship with palmiet. They use water found in the peatlands to irrigate their land, but simultaneously cut away the palmiet plants themselves in effort to limit encroachment into their land. In the past, the leaves of the palmiet have been used as fi bres, but this use is not very extensive nowadays. The fi bre, called palmite, is the original source of the name for this plant.

Species in the spotlight

The habitat creatorSieben, E¹

¹ University of the Free State, South Africa

The palmiet (Prionium serratum) (LC) is

endemic to South Africa. It is common

in the Western Cape province in South

Africa. © E. SIEBEN

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E ichnornia crassipes, or water hyacinth, is an aquatic plant within the family Pontederiaceae and is

native to the Amazon basin. This species, which is now widespread throughout much of Africa, was fi rst recorded in western Africa in 1985 where it was recognised as a problem species within a few years (Ouédraogo et al. 2004). The adverse impacts of the species in Africa have led to it being called the “Tiger of Bengal” (NAS 1976) or “Green peril of Congo” (Lebrun 1959). The rapid spread of water hyacinth poses a signifi cant threat to water supplies and the use of inland water bodies, such as for fi shing or transport, throughout the western Africa region. The Inter-State Committee for the Fight Against Drought in the Sahel (CILSS) prioritises water storage and its sensible management as a key component in their food self-suffi ciency policy and the fi ght against poverty (ECOWAS 1994). The control of water hyacinth infestation throughout the region has, therefore, become an imperative (Ouédraogo 1996).

The harmful effects of this plant are demonstrated through the following specifi c examples from various water bodies in western Africa. For example, in some key fi shing areas in the west of Burkina Faso, the rapid spread of water hyacinth and its subsequent impacts on the free movement of fi shing boats effectively paralyzed all related human activities across 15 kilometres of the Son River. This resulted in an estimated loss of earnings amounting to EUR 27,500 a year (Ouédraogo et

al. 2004). In other places, increases in biomass and the associated high rates of evapotranspiration due to water

hyacinth proliferation have reduced the capacity of water bodies to meet the needs of men and animals. For example, in the Ouagadougou dams (Burkina Faso), annual water loss due to infestation of nine hectares by water hyacinth amounted to 292,329m3 with an estimated associated cost of EUR 80,000, according to the National Water and Sanitation provider (ONEA). The biomass of water hyacinth covering the area was estimated to be 3,500tonnes, representing a major obstruction to free movement across the water body and posing a serious threat to the functional ecology of such freshwater systems that represent an important resource for many people across the region.

The water hyacinth is highly adaptive and has proved resistant to the many varied efforts to eradicate it from the region. It has a cyclical growth pattern within the two distinctive seasons typical to western Africa. Plants behave as hemicryptophyes as the rizome and vegetative parts become dormant during the unfavourable dry season, but rapidly activate when conditions become more favourable in the

humid season, at which time the plant spreads rapidly. There is also a signifi cant germination of seeds in the late wet season. Hence, the water hyacinth shows a perfect adaptation to the Sahel environment, being able to withstand water shortage and droughts and to ensure its survival and rapid expansion through massive production of seeds and vegetative growth (Ouédraogo et al. 2004). These factors are of major importance when considering new strategies and methods for controlling these plants in the Sahelian countries.

The control of water hyacinth and other invasive plants through integrated strategies is already underway. Technologies generated in the fi eld do, however, need to be constantly adapted to meet local peculiarities and to take account of climatic differences. Despite clear successes, current methods for controlling this plant need to be improved through further research in order to make strategies more effi cient and cost-effective. An integrated approach including reduction of nutrient loading of inland waters, and biological and chemical control is recommended.

Species in the spotlight

Water hyacinth, a threat to the freshwater biodiversity of western Africa

Ouédraogo, R.L.¹

¹ Institute de l’Environment et de Recherches Agricoles, Burkina Faso

Water hyacinth in Burkina Faso. © R.L. OUEDRAOGO

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