Rhododendron conservation in botanic gardens 583


TABLE 3 Botanic gardens conserving living collections of . 10 ss. Maddenia taxa, in descending order of total number of conserved taxa, with the number of taxa in each IUCN Red List category in contrast to that in cultivation globally. Numbers in parentheses are number of taxa in cultivation/number of total taxa in the category.


Botanic garden


University of California Botanical Garden at Berkeley


Dandenong Ranges Botanic Garden Dunedin Botanic Garden RhodoBG_023 Pukeiti Garden


Royal Botanic Gardens Kew4 Blue Mountains Botanic Garden Germplasm Bank of Wild Species St Andrews Botanic Garden


University of British Columbia Botanical Garden


Country


Rhododendron Species Botanical Garden USA Royal Botanic Garden Edinburgh2


UK USA Australia


Number of conserved taxa (55/65)


48 37 33


New Zealand 27 Australia


New Zealand 23 UK


Australia China UK


Canada


31 25 19


19 14 14 11


IUCN Red List status1 CR


EN


(3/3) 3


2 3


3 1 2 1 1 2 1 0 0


(2/2) 2


1 1


1 1 1 1 0 0 1 0 0


VU


(13/13) 12


10 8


5 7 5 4 4 4 0 4 3


NT


(4/4) 4


3 3


3 2 2 2 1 2 2 1 3


DD


(9/12) 6


4 2


4 2 1 2 1 0 1 1 0


LC


(18/20) 18


15 14


14 13 13 12 12 10 8 8 5


1CR, Critically Endangered; EN, Endangered; VU, Vulnerable; NT, Near Threatened; DD, Data Deficient; LC, Least Concern; NE, Not Evaluated. 2Including Royal Botanic Garden Edinburgh at Edinburgh, Logan and Benmore. 3Garden anonymised as permission for naming the garden was not acquired. 4Including Royal Botanic Gardens Kew at Richmond and Wakehurst.


available for different taxa, hence our capturing of distribu- tions could differ amongst species. The distribution of ss. Maddenia is often not well described to specific localities but rather to broad administrative units, especially in areas where few taxa have been found (Fig. 1a; Supplementary Material 3). Assessment of ecogeographical representation requires


wild collections to be well documented. Adequate geograph- ical data, especially with precise coordinates of the source specimens, and regular updates on the living status of accessions are essential to record in wild collections. However, ex situ collections usually suffer from poor docu- mentation, and the extent of the documentation of details of wild collections differs amongst botanic gardens. This causes difficulties in tracing the origins of wild collections and limits the accuracy of evaluations of captured diversity.


Recommendations for urgent conservation action of subsection Maddenia


Wesuggest that relevant botanic gardens collaborate to con- serve subsection Maddenia by: (1) investigating and/or establishing ex situ collections in their countries of origin; (2) sharing ex situ data with BGCI and the Global Conser- vation Consortium for Rhododendron;(3) establishing an accessions database with fields for individual gardens to facilitate genus-wide analyses; and (4) developing a meta- collection of ss. Maddenia across sites and nations to pool wild accessions for the conservation of genetic diversity.


Field investigation and wild sampling should be further developed, particularly in the border regions between countries of origin. Genetic information could be added to the database of wild accessions developed in this study to underpin research within the global conservation network. Based on the criterion of three wild accessions per taxon


we propose urgent action: (1) to establish ex situ collections for the three Data Deficient taxa that are not in cultivation (R. amandum, R. yaogangxianense, R. yizhangense) unless they are reassessed as Least Concern; (2) to obtain wild col- lections for the two Vulnerable (R. roseatum, R. sinonut- tallii) and two Data Deficient taxa (R. linearilobum, R. rhombifolium) that currently have no wild accessions conserved; and (3) to extend the ecogeographical range of wild sampling for the 10 taxa that are threatened or at risk but with documented wild accessions from fewer than three wild sources, including two Critically Endangered taxa (R. coxianum, R. fleuryi), two Endangered taxa (Rhododendron fletcherianum, R. kiangsiense), three Vulnerable taxa (Rhododendron dalhousiae var. rhabdotum, R. taronense, Rhododendron walongense) and three Data Deficient taxa (Rhododendron chunienii, Rhododendron ciliipes, R. kuomeianum). In this study we have identified the gaps in knowledge


of Rhododendron ss. Maddenia in ex situ conservation, with a focus on the ecogeographical representation in ex situ collections for guiding further conservation efforts. We find that botanic gardens are important repositories for this group: 86% of the taxa, including all threatened taxa,


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 NE


(6/11) 3


2 2


1 1 1 1 0 1 1 0 0


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