Rare species rediscovered in the dancing heat waves of the Namib

Text and Photographs Oliver Halsey

T he seemingly inhospitable gravel plains of the Namib Desert extend over vast distances. 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 unobstructed horizon extends in all directions, save southwest, where its line thickens 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 around 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. The plains are home to an impressive variety of beetles, lizards, geckos and other small life forms in burrows, and racing along the surface. They are examples of superbly adapted desert wildlife which can obtain the water that they need to survive without drinking often, 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.

Over 40 years ago, in 1972, on the gravel plains of the Namib- Naukluft Park a small plant was discovered by Ernest Robinson, a research assistant at Gobabeb Research Centre at the time. Robinson collected two specimens. They were sterile but from the tubers they were later identified as a Raphionacme species. Raphionacme is a genus in the family Apocynaceae of some 36 species, six of which occur in Namibia. 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 years following their discovery in an attempt to locate more, but to no avail – the plants were never seen again.

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. It was after heavy rainfalls, and again on the gravel plains of the central Namib. Examinations later revealed that the plants collected by Hänel were indeed a new species of Raphionacme. The new taxon was then named after Hänel, Raphionacme haeneliae – 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, after heavy rainfall in April 2009, Dr Antje Burke, a botanist in Namibia, led a team to determine the conservation status of the plant for the IUCN Red List. The team managed to locate several specimens and determined that the species 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.

In June last year (2016) heavy rainfall descended once again on parts of the Namib and the peculiar, desert-adapted miracle revealed itself again. After 18 mm of rainfall around Gobabeb in just two days, the research centre’s Executive Director, 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, Dr Maggs-Kölling finally came across the elusive plant. Since the infrequent sightings were always made after heavy rains, it seemed probable that the plant sprouts only after a significant amount of rain, the tuber hidden away underground most of the time.

After sufficient rainfall the flowers of R. haeneliae apparently are the first to penetrate the soil surface. The searches after the spectacular rainfall of 2016 revealed no R. haeneliae flowers, however. It is possible that rodents and/or game had eaten them because rather remarkably there was no trace left of the plants (such as fruit remains) – which is unusual due to extremely slow decomposition rates in the arid desert environment. But 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 reason why the plant is seldom seen.

Numerous scientists at Gobabeb have been trying to locate populations of R. haeneliae in the months after the rain, keeping track of their locations with GPS. In the 2016 survey, R. haeneliae was located at several additional sites, although it still seems 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 rain, with far bigger numbers found at Ganab. Shortly after the rain Ganab had an abundance of newly-bloomed desert flowers and other desert-adapted flora, such as a flowering Hoodia currorii – a desert endemic succulent that has potential commercial use as a hunger suppressant.

There are many unanswered questions surrounding this plant. “Raphionacme haeneliae is obviously perennial”, Dr Maggs-Kölling says. “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 Fynbos, a vegetation type in the Cape region, South Africa. In such cases the flowers are carried close to the soil surface and are thus accessible to small rodents. The same could be true for R. haeneliae, which may explain its abundance in rodent-disturbed soil.

Among the more interesting aspects 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 Dr Maggs-Kölling. Scientists can refer to what they know about other species in the Raphionacme genus, and thus deduce certain functions and attributes regarding 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 sought-after by the indigenous Ju/’hoansi people as a juicy snack. Other species of Raphionacme such as R. lanceolata and R. velutina produce similar tuberous rootstocks. The latter is the plant responsible for

the archetypal image of San (Bushman) life: squeezing a tuber to produce a thirst quenching liquid. In previous times, being able to recognise the stalks of R. velutina in the sandy soil was a matter of life and death for many San people. Archaeological evidence of human activity dates back to over 8,000 years at Mirabib, a site with R. haeneliae in the vicinity. If the tubers are edible, it is reasonable to assume that they may have been a lifeline for people wandering the desert plains thousands of years ago.

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 sprout after heavy rainfall and last for about two to three months before drying up. The rarity of heavy rainfall combined with the remote location in which the plant is found are likely reasons 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 that 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.

This article was first published in the Travel News Namibia Autumn 2017 issue.