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Raphionacme haeneliae - Rare species rediscovered

Written and photographed by Oliver Halsey, to view more of his work visit Oliver Halsey Website

The seemingly inhospitable gravel plains of the Namib Desert extend over a vast distance. Standing alone in the middle of this barren landscape can be a daunting experience. At a glance, there seems to be no sign of life in the hot, dusty, rocky, and apparently endless plains that surround you.

The line of the horizon extends in all directions, save southwest, the line thickening with the dunes of the Namib Sand Sea, just visible through the dancing heat waves. It isn’t until your gaze turns to the ground beneath your feet that the smaller signs of life appear. Small burrow holes pockmark the surface, so uniform a field that the pattern remains invisible to the casual passer-by. In burrows, and racing along the surface, the plains are home to an impressive variety of beetles, lizards, geckos, and other small life forms. These are examples of superbly adapted desert wildlife, which can obtain the water that they need to survive without often drinking, if at all. One of the last things you would expect to see in this arid wilderness is a bright green plant - the quintessential illustration of life.

 RH1A lone R. haeneliae on the vast gravel plains of the Namib Desert.

Over 40 years ago in 1972, on the gravel plains of the Namib-Naukluft Park, a small plant was discovered and collected by Ernest Robinson, a research assistant at Gobabeb Research and Training Centre at the time. Robinson collected two specimens; they were sterile but later identified as a Raphionacme species from the tubers. Raphionacme is a genus in the family Apocynaceae of some 36 species, six of which occur in Namibia (Klaassen & Kwembeya, 2013). The two specimens that Robinson collected were then locked away at the University of Fort Hare’s Herbarium for several years. Searches were made in the subsequent years following their discovery in an attempt to locate more, however it was to no avail - the plants were never seen again.

JasperJasper Vannueville of Vives University College, Belgium attempts to locate a plant with GPS on the desolate gravel plains of the Namib.

More than two decades after Robinson’s original find, Christine Hänel, an intern at Gobabeb, found a plant that looked suspiciously similar to Robinson’s find. It had been after heavy rainfall, and again on the gravel plains of the central Namib. Hänel collected the plants, which were later determined, revealing that they were indeed a new species of Raphionacme. The new taxon was then named after Hänel, Raphionacme haeneliae Venter & Verhoeven - a tribute to the rediscovery of this secretive species.

Since the publication of the type description, the mysterious plant seemed to have vanished into hiding again. Many years later in April 2009, after heavy rainfall, Dr Antje Burke, a botanist in Namibia, lead a team to determine the conservation status of the plant for the IUCN Red List. The team managed to locate several specimens and determine that it should be listed as “Least Concern” due to no perceived threats associated with it, however it is considered “Rare” due to its extremely limited distribution (Loots & Burke, 2009).

This past June, heavy rainfall descended once again on the Namib, and the peculiar, desert-adapted miracle revealed itself once again. After 18 mm of rainfall around Gobabeb in just two days, Executive Director of Gobabeb, Dr Gillian Maggs-Kölling decided to search for the mysterious plant. Using a photograph taken in 1996 to align the rocky outcrops on the horizon, Maggs-Kölling finally came across the elusive plant. The infrequent sightings have always been after heavy rainfall, making it probable that the plant sprouts only after a significant amount of rain has fallen, the tuber hidden away underground for most of the time.

RH2Dr Gillian Maggs-Kölling and Meg Schmitt (foreground) of Gobabeb try to locate the small plant on the extensive plains.

After enough rainfall, the flowers of R. haeneliae are apparently the first to penetrate through the soil surface (Venter & Verhoeven, 1996). The searches following the spectacular rainfall of 2016 revealed no R. haeneliae flowers. It is possible that rodents and/or game had grazed them as the plants rather remarkably left little trace (such as fruit remains) behind - unusual due to extremely slow decomposition rates within the arid desert environment. However, there are numerous examples of plants that bloom many years apart and there is a strong possibility that R. haeneliae does not flower regularly. With only the inconspicuous green leaves penetrating the surface, this could be another possibility as to why the plant is seldom seen.

RainbowRain descends over the Namib Sand Sea, producing the rare sight of a double rainbow in the desert.

RH7Raphionacme haeneliae.

RH3Close-up of the leaves of R. haeneliae.

As well as large game, the central Namib is home to a number of burrowing creatures such as aardvarks, foxes, gerbils, ground squirrels, lizards, mice and porcupines. Disturbed soil has been observed in areas where R. haeneliae has been sighted, and this seems to be linked to a greater abundance of the plant, potentially encouraging its growth.

RH4Soil disturbance is prevalent where R. haeneliae grows. Here, the plant can be seen next to what is thought to be evidence of rodent burrowing.

Numerous scientists at Gobabeb have been trying to locate populations of R. haeneliae in the subsequent months after the rain, keeping track of their locations with GPS. In the 2016 survey, R. haeneliae has been located at several more sites, although it is still seemingly endemic to the gravel plains of the central Namib.

In June 2016, more than 40 mm of rain fell at Ganab, compared to 18 mm at the other known R. haeneliae locations. The plants seemed to respond positively to rainfall, with Ganab hosting the plant in far greater numbers. Shortly after the rain, Ganab hosted abundant newly-bloomed desert flowers and other desert-adapted flora, such as a flowering Hoodia currorii - a succulent, desert endemic that has potential commercial use as a hunger suppressant.

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Hoodia   A flowering Hoodia currorii plant - a species historically used by the indigenous San people as a hunger suppressant.

Ganab FlowersSmall desert flowers (Grielum sinuatum) in bloom, two months after heavy rainfall.

EV  A top Thomasberg, Ganab – Euphorbia virosa plants look out over the plains to below, where R. haeneliae grows.

Ganab LandscapeMany of the small, green Raphionacme plants were found dotted amongst the landscape of Ganab.

There are many unanswered questions surrounding this plant. “Raphionacme haeneliae is obviously perennial”, Maggs-Kölling says, “[and] we want to monitor known sites in the future to understand their distribution patterns. We haven’t yet seen the pollination mechanism of the plant so its reproductive strategies are uncertain.” Mice pollinate some taxa in the genus Protea, a dominant element of the Fynbos, a vegetation region in the Cape, South Africa (Proctor, Yeo, & Lack, 1996). In such cases the flowers are carried close to the soil surface and are thus accessible to small rodents. The same could be said for R. haeneliae, which may explain its abundance in rodent-disturbed soil.

SeedRaphionacme haeneliae seeds - hairy comae (tufts of hairs) indicate wind dispersal. Photo courtesy: E. Marais.

Among the more interesting components of this mysterious plant are its familial relations. “We are to look at closely related taxa in the family Apocynaceae and whether they are edible or not. Lots in the family are very toxic”, says Maggs-Kölling. Scientists can refer to what they know about other species within the Raphionacme genus, and thus assume certain functions and attributes regarding R. haeneliae.

RH5Leaves of R. haeneliae.

Fockea is a genus of plants indigenous to southern Africa. They are known collectively as “water roots” and have large, milky sap-producing tubers, much like R. haeneliae. The tuber of F. angustifolia is a sought-after food for the indigenous Jul’hoansi people, providing “juicy, crisp flesh” (Leffers, 2003). Other species of Raphionacme such as R. lanceolata and R. velutina produce similar tuberous rootstocks, the latter being the plant responsible for the archetypal image of San bushman life - the squeezing of the tuber to produce a thirst quenching liquid. Historically for many San people, being able to recognise the stalks of R. velutina in the sandy soil was a matter of life and death (Leffers, 2003). Archaeological evidence of human activity dates back to over 8,000 years at Mirabib (Sandelowsky, 1974), a site in the vicinity of R. haeneliae. If the tubers are edible, it is reasonable to assume they may have been a lifeline for people wandering the desert plains thousands of years ago.

Tuber 2Jessica Sack, research technician at Gobabeb digs to remove the tuber of R. haeneliae.

TuberR. haeneliae and its tuber.

The discovery of a new species, or in this case, the rediscovery of a relatively recently described but ever-elusive species, is always exciting. With many plants the world over providing significant benefit for humans, further research on R. haeneliae could potentially reveal hidden uses or provide answers to yet-unknown questions.

What we understand so far is that the leaves of R. haeneliae only spout after heavy rainfall and last for about two to three months before drying up. Rare heavy rainfall combined with the remote location in which the plant is found are likely reasons as to why it is seldom seen. After the recent rediscovery, Gobabeb aims to continue to locate and monitor R. haeneliae through annual surveys. It is hoped Gobabeb’s scientists will be able to unravel some of the secrets that this miraculous plant holds, allowing for a more concrete understanding of this green mirage on the plains.

DeadThe leaves of R. haeneliae start to turn yellow and fall off two months after its initial sprouting.

RH8The vibrant green leaves of R. haeneliae.

Acknowledgments


 

Special thanks are extended to: Gobabeb Research and Training Centre for providing the necessary means to locate and photograph Raphionacme haeneliae. Dr Gillian Maggs-Kölling, Executive Director of Gobabeb and Dr Eugene Marais, Chief Curator of the National Museum of Namibia for locating and recording the known locations of the species, as well as for sharing their botanical knowledge. Ms Sonja Loots and Dr Antje Burke for undertaking population size estimates for IUCN and the willingness to share this information. Ms Frances Chase of the National Botanical Research Institute, Windhoek for providing Gobabeb with current information and publications regarding R. haeneliae. Ms Bryn Morgan of Dartmouth College, New Hampshire, USA for mapping the GPS coordinates of R. haeneliae to view its current, known distribution within the Namib-Naukluft Park.

 

References


Klaassen, E. & Kwembeya, E. (eds) (2013) A checklist of Namibian Indigenous and Naturalised Plants. National Botanical Research Institute Occasional Contributions 5. 171.

Leffers, A. (2003) Gemsbok Bean & Kalahari Truffle Traditional plant use by Jul’hoansi in North-Eastern Namibia. Windhoek, Gamsberg Macmillan Publishers. 110 – 166.

Loots, S. & Burke, A. (2009) Plant Red List Data of Namibia. National Botanical Research Institute, Windhoek. (Unpublished data sheets).

Proctor, M. Yeo, P. & Lack, A. (1996) The Natural History of Pollination. London, Harper Collins Publishers. 258 – 261.

Sandelowsky, B.H. (1974) Archaeological Investigations at Mirabib Hill Rock Shelter: South African Archaeological Society Goodwin Series 2. 67 – 69.

Venter, H.J.T. & Verhoeven, R.L. (1996) Raphionacme haeneliae (Periplocaceae), a new species from the Namib Desert, Namibia: South African Journal of Botany 62(6). 316 – 320.

 

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