Rediscovery of thewaterlily Nymphaea thermarum Eb. Fisch. in Rwanda THOMAS ABELI * 1 , 2 , 3 ,S AR A H MARIE MÜLLER 4 and S IEGMAR S EI D E L 4
Abstract Nymphaea thermarum Eb. Fisch. (family Nymphaeaceae) is a small waterlily endemic to Rwanda that has been categorized as Extinct in the Wild since 2010. We report the rediscovery of N. thermarum in July 2023, not far from its locus classicus, identify the current and potential threats to the wild population (mining and overharvesting by collectors, respectively) and recommend the urgent conservation measures and research required to save the species from extinction. The species occupies small muddy ditches fed by hot spring water used for avocado plantations and fish pools. The population comprises hun- dreds of individuals, including reproductive adult plants, and seedlings. In the short term, conservation actions should include land protection, negotiation to ensure that sufficient water is reaching the habitat of N. thermarum and the reassessment of the species on the IUCN Red List, probably as Critically Endangered. In the medium term, the creation of a nature reserve, the restoration of the areas already affected by mining, and the reintroduction of N. thermarum to its original site would support long-term in situ conservation of the species. Further research should clarify the total and effective population size, population structure, ecology and genetics of this species.
Keywords Conservation measures, East Africa, Extinct in the Wild, Nymphaea thermarum, rediscovery, threat assess- ment, waterlily, wetlands
A
ccording to the IUCN Red List Categories and Criteria (IUCN, 2012), species categorized as Extinct in theWild
are those that survive only under human care in ex situ facil- ities or naturalized outside their native range. Although ex situ facilities such as botanic gardens and seed banks limit plant species extinctions (Abeli et al., 2020), there are several problems associated with long-term ex situ culti- vation that make the reintroduction of Extinct in the Wild species difficult (i.e. low genetic diversity, inbreeding and adaptation to ex situ conditions; Ensslin & Godefroid,
*Corresponding author,
thomas.abeli@uniroma3.it 1Department of Science, Roma Tre University, Rome, Italy 2IUCN Species Survival Commission Conservation Translocation Specialist
Group 3IUCN Species Survival Commission Freshwater Plant Specialist Group 4Rwanda Centre and Office for Africa Cooperation, University of Koblenz, Koblenz, Germany
Received 12 September 2023. Revision requested 15 November 2023. Accepted 30 November 2023. First published online 21 February 2024.
2020;Tremblay etal., 2022). As a result of these problems, and combined with the probable destruction or degradation of their original habitats, the rediscovery of species that are Extinct in theWild has a significant impact on their conser- vation because it facilitates the coupling of ex situ and in situ conservation, including site protection, wild population re- inforcement and revitalization of ex situ collections with new genetic material from the wild (Smith et al., 2023). Nymphaea thermarum Eb. Fisch. (family Nymphaeaceae)
is a small, iconic waterlily endemic to southern Rwanda that has become amodel for the study of the evolution of early an- giosperms (Povilus et al., 2020). The species was discovered and described in 1987 by Eberhard Fischer (Fischer, 1988; Fischer & Magdalena, 2011) near the Mashyuza hot spring in the area ofNyakabuye, RusiziDistrict. Nymphaea thermar- um was last seen in its original site in 2008, and attempts to find it in the wild since then have been unsuccessful, lead- ing to its categorization as Extinct in theWild on the IUCN Red List in 2010 and 2019 (Juffe, 2010; Fischer et al., 2019). The species was initially cultivated and propagated at the Botanic Gardens of the University of Bonn, Germany, from several plants collected at the time of discovery, and it is cu- rrently cultivated in at least 13 botanical gardens (BGCI, 2023). On 29 July 2023, authors TA and SMM, and Jean Marie Habiyakare, visited the area of the Mashyuza hot spring and found N. thermarum in a new site west of its original loca- tion, on private land (Plate 1). Given the interest of collectors and waterlily enthusiasts for this species (which is sold on the horticultural market for c. EUR 500/plant) the exact lo- cation of the discovered population is not provided here, and will not be disclosed until protection measures are es- tablished. On 29 August 2023, author SS visited the site and completed preliminary observations on the population status of N. thermarum. We found N. thermarum in small ditches and ponds in
an area currently occupied by small plantations of banana, mango and avocado, and fishponds. We assessed the popu- lation to be healthy and to comprise hundreds of individ- uals, including reproductive adult plants, and seedlings (Plate 1). The area occupied by the species is c. 4,600 m2. There are serious and imminent threats to this wild N.
thermarum population. Mining by a local cement factory (the property of which is c. 10mfrom a group of N. thermar- um) is the most significant threat, and the mining has al- ready affected the population directly through excavations and road development and indirectly through impacts on the springs feeding the ditches and ponds where the species
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http://creativecommons.org/licenses/by-nc-sa/4.0),which permits non-commercial re-use, distribution, and reproduction in anymedium, provided the sameCreativeCommons licence is used to distribute the re-used or adapted article and the original article is properly cited. The written permission of Cambridge University Press must be obtained prior to any commercial use. Oryx, 2024, 58(5), 600–602 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323001837
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