3 April 2017
Revisiting the Madagascan suicide palm: a spectacular discovery
In a surprise final part of the Tahina spectabilis story, Lauren Gardiner reveals a stunning discovery the team made in Madagascar last year after their return to the original site at Antsingilava, which they can only now reveal and which has just been published in the international conservation journal, Oryx.
At the end of last year, two Kew Science blog posts, Revisiting the Madagascan suicide palm and Revisiting the Madagascan suicide palm: a decade on, told the story of the discovery of the Critically Endangered palm Tahina spectabiis, and Kew’s return to the remote site a decade later.
At the end of 2014, photographs of a huge-leaved fan palm, taken on a mobile phone had been sent to colleagues at Kew by a collaborator, Theophile Rajaonilaza, from a site near the town of Maromandia. The plants were identified as almost certainly being Tahina, but intriguingly this was a completely different location for the species, more than 80 km northeast of the original location, and in a fragment of forest in a valley, rather than around a limestone karst formation (tsingy).
Why on earth would you try to take a car to Amparahibe?
After meeting Theophile and leaving the road near Maromandia, we travelled on increasingly rudimentary zebu cart tracks towards the village of Amparahibe, approximately 10 km away. The lack of natural vegetation, visible recent burning, and eroded soils did not bode well for what we would find on this part of the trip. A local woman called us crazy and asked ‘Why on earth would you try to take a car to Amparahibe?!’ as we passed. But we made it, and we were generously received by the village elders, to whom Theophile explained our mission to look for Tahina here, the importance of this species and why it needed to be protected.
The plot thickens…
That afternoon, led by a group of local people, we went to see the closest individual of the mysterious palm, an isolated individual on a hillside. We found a young, stunted-looking palm, surrounded by scrubby, part-burned vegetation, with leaves up to two metres across. We weren’t entirely sure that this was Tahina spectabilis – but it did not match any other known genus either, with rounded leaflets tips, relatively short petioles, and lacking the usual striking distichous leaf arrangement (leaves arranged in one plane, rather than being arranged spirally).
The plant had been deliberately damaged, with digging at the base, and leaves removed at the petiole with a machete. The villagers told us that the palm heart (the growing point, or apical meristem, found at the top of the trunk) was good to eat - alarming news to hear for a Critically Endangered palm species. Harvesting the heart of such a palm, which only has a single growing point, will kill the entire plant. Whatever species the palm turned out to be, if the local people were eating it, this would be a huge threat to its survival. The large fan-shaped leaves are also used by local people occasionally as mats to sit on at ceremonial occasions, and as temporary umbrellas.
Hiking in the other direction from the village the next morning, the villagers showed us the second isolated individual. This plant was actually in a worse condition and even more precarious situation, similarly stunted but with more leaves removed. The vegetation all around had recently been cut and the surrounding steep hillsides burned, and similar digging was seen at the base of the stunted trunk.
A remarkable discovery confirmed
Puzzled and worried by the two ‘Tahina’ plants we had seen so far, it was not until we reached a fragment of humid forest that we could unequivocally confirm the presence of Tahina spectabilis. Following, and repeatedly crossing, the shallow river meandering its way through the dappled shade, Theophile suddenly called out from ahead and reappeared, beaming with excitement. Ahead lay a giant – a 12 metre tall adult Tahina spectabilis, unmistakeable and with a small grove of young Tahina plants and seedlings below. As we knew from Antsingilava, Tahina can grow to at least 18 metres in height, but there the plants are surrounded by other large individuals and towering tsingy cliffs. At the new site the surrounding trees were smaller and there were no rock-faces, so the scale looked very different. In this kind of vegetation, the largest Tahina towered over everything else – including us.
Theophile’s reaction was genuine surprise and revelation. When he had been here before he had not actually seen this group of plants – approximately 40 m away was the small group of juveniles he had photographed on his mobile phone. He had missed this second group with its one huge trunked individual before, but he recognised it immediately from the images of Tahina sent to him by Kew.
The team surveyed the site in detail, taking pieces of leaf material for DNA samples from each individual. Altogether, including seedlings and the two isolated individuals seen away from the forest, we found a total of 27 Tahina spectabilis plants near Amparahibe. At the main site, there was more evidence of leaf harvesting and digging at the base of trunks and the largest of the group of juveniles Theophile had photographed in 2014 had since been felled. The local people thought this was likely to have been for the palm’s edible heart.
The villagers also told of foreigners visiting the area and specifically asking for, and buying plants collected from the forest - and how they would collect plants from the wild and take them to the roadside nurseries to sell.
Future directions for the conservation of Tahina
Future work will include studying the population genetics of the individuals found at the new site, and those of the plants at Anstingilava, to study the genetic differences within and between the populations. The existence of the new population is likely to improve the likelihood of genetic diversity being discovered between the sites. This, in turn will improve the chance that seed produced in the future may be genetically more resilient, and efforts to collect seed for ex situ conservation from the new population will be important to maintain this diversity.
The Tahina population found growing at such a distance from the original site improves the likelihood that further populations may exist elsewhere. The new site is also so different from the original site, that the new environmental and habitat conditions, will allow us to predict whether or not the species might grow in other remaining vegetation fragments in northwest Madagascar, and we can better target efforts to search for Tahina at other sites.
Even with an expanded geographic distribution and more individuals of Tahina being found, with fewer than 50 mature adult individuals known in the wild globally, the conservation status of the species is still Critically Endangered (using the IUCN Red List of Threatened Species Categories and Criteria). As such this species continues to need active conservation efforts – especially in the face of clear threats at the second location, from harvesting the leaves, to cutting the trunks for palm heart, and poaching of wild plants for foreign buyers.
Initial discussions about the future conservation of Tahina, with the elders and the wider community at Amparahibe went very well. A follow-up trip by other members of the Kew Madagascar team in October 2016 further discussed how the community, alongside Kew can work together, and integrate community development with conservation in the area.
References
Gardiner, L.M., Rabehevitra, D., Letsara, R., & Shapcott, A. (2017). Discovery of a second population of the Critically Endangered Madagascan suicide palm Tahina spectabilis. Oryx 51(2): 205-206. DOI: 10.1017/S003060531700014X. Available online
Gardiner, L.M., D. Rabehevitra, R. Letsara, A. Shapcott. (accepted, to be published June 2017) Tahina spectabilis: a new discovery in Madagascar ten years on. PALMS (Journal of the International Palm Society) 61(2): 69-82.
Acknowledgements
Generous support from the Mohamed bin Zayed Species Conservation Fund made this expedition and the follow-up work possible.
Individual thanks go to the following: The Kew Madagascar team, especially Helene Ralimanana, David Rabehevitra, Theophile Rajaonilaza, and Roger Rajaonarison; Alison Shapcott (University of the Sunshine Coast, Queensland, Australia); Rokiman Letsara (Parc Botanique et Zoologique de Tsimbazaza and Californian Academy of Sciences); Kew Madagascar’s Research Leader, Stuart Cable; Head of Conservation Science, Colin Clubbe; Alain Andrianandraina and Manitra Razafinahatratra from VERAMA (part of UNIMA group); Cedric de Foucault from Anjajavy Resort; and Joseph from the COBA of Antonibe.