Rhododendron diversity conservation in global botanic gardens: a case study of Maddenia species L IN G HU * 1 ,MARION MACKAY 1 ,SUSAN E. GAR D I NER 2 and J ENNI FER A. TAT E 1
Abstract Effective ex situ conservation of plants in botanic gardens requires sufficient wild accessions to represent wild diversity. In Rhododendron L. (Ericaceae), c. 64%of the taxa are threatened or require field investigation. As a case study of the analysis of ex situ conservation gaps we used ecogeo- graphical representation as a proxy for genetic representa- tion in ex situ collections of the 65 taxa of Rhododendron subsection Maddenia. We compiled the first list profiling both wild distributions and ex situ wild collections of all taxa in subsection Maddenia. Our results reveal that 55 Maddenia taxa are in cultivation. Of the 18 threatened taxa all are in cultivation but nine require further collection to capture adequate wild diversity. There are 12 Data Deficient taxa: these await further field investigation of wild populations and nine of them require wild collections to conserve genetic diversity. The UK, the USA, Australia, New Zealand and China are the top five countries holding ex situ collections of subsection Maddenia; in these coun- tries nearly 66%of the ex situ sites hold.86%of the global living collections of subsection Maddenia.We recommend that wild collections of endemic species of subsection Maddenia should be established in all 10 countries of origin and that data should be shared internationally for meta- collections. In addition to proposing priorities, our case study highlights the challenges facing data and collection management to help achieve effective ex situ conserva- tion for Rhododendron species.
Keywords Ecogeographical representation, ex situ conser- vation, genetic representation, living collection, Maddenia, prioritization, Rhododendron, wild accession
The supplementary material for this article is available at
doi.org/10.1017/S0030605324000759
Introduction P
lant biodiversity conservation was prioritized for urgent action at the United Nations Biodiversity Conference CoP 15, with a particular focus on the
*Corresponding author,
gloria_hu95@outlook.com 1School of Agriculture and Environment, Massey University, Palmerston North,
New Zealand 2The New Zealand Institute for Plant and Food Research Limited, Fitzherbert Science Centre, Palmerston North, New Zealand
Received 16 April 2023. Revision requested 14 September 2023. Accepted 17 April 2024. First published online 4 November 2024.
development of the post-2020 global strategy for plant conservation (CBD, 2021). As a component of integrated plant conservation, ex situ conservation not only con- serves plant diversity but also supports habitat restoration (Havens et al., 2006;Westwoodetal., 2021). The genetic variation in ex situ collections at the species, population, individual, and allelic levels could be drawn from to facili- tate the adaptation of species to potential environmental changes in habitat, as well as safeguarding against intro- duced diseases and pests (Sharrock, 2020). Botanic gardens (including arboreta) are key repositories
of living collections for plant ex situ conservation (Havens et al., 2006;O’Donnell & Sharrock, 2017; Sharrock, 2020; Hudson et al., 2021; Westwood et al., 2021). Target 8 of the Global Strategy for Plant Conservation (CBD, 2010) directs that at least 75% of threatened species be con- served in ex situ collections (preferably in their countries of origin), with over 20% available for restoration pro- grammes. Examining the ex situ conservation status of species against Target 8 and identifying gaps enables botanic gardens to support ex situ conservation more effec- tively (Godefroid et al., 2011; Linsky et al., 2022). According to analyses of data from the largest plant conservation network in the world, Botanic Gardens Conservation International (BGCI), plant collections in global botanic gardens face problems, such as species being held dis- proportionately in temperate locations, outside their country of origin and in one institution only (Mounce et al., 2017; Sharrock, 2020). To overcome these problems, ex situ collections require scientific management to maxi- mize conservation effectiveness. Afundamental underpinning for effective ex situ conser-
vation is a sufficient number of wild-source accessions that represent the wild diversity of species (IUCN SSC, 2014; Mounce et al., 2017; Maxted et al., 2020; Wei & Jiang, 2021;Westwood et al., 2021). The limited space and facilities of botanic gardens have to be allocated to prioritized species (Heywood, 2017; Sharrock, 2020). Factors such as species richness, taxonomic distinctiveness, vulnerabilities and threats in the wild as well as ongoing ex situ conservation activities have been considered to determine priorities for several plant genera (Kozlowski et al., 2012; Toppila, 2012; Hoban et al., 2018; MacKay et al., 2018; Linsky et al., 2022). To estimate the genetic representation (captured gen- etic variation) in ex situ collections, the concept of the eco- geographical representativeness of wild accessions has been proposed as a surrogate when the genetic diversity of the species is unknown (Rae, 2011; Griffith et al., 2015, 2020;
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (
http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution and reproduction, provided the original article is properly cited. Oryx, 2024, 58(5), 576–586 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324000759
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