580 L. Hu et al.
TABLE 1 Number of botanic gardens in the countries of origin of Rhododendron subsection Maddenia. Countries are listed in descending order by number of taxa. Numbers of gardens with ss. Maddenia or Rhododendron collections are from PlantSearch (BGCI, 2021b), and numbers of BGCI or non-member botanic gardens are from BGCI GardenSearch (BGCI, 2022a).
Country China
Number of ss. Maddenia taxa
Myanmar 20 India
Viet Nam 13 Bhutan
Thailand 4 Nepal Laos
3
Bangladesh 2 Indonesia 1
45 19 7 3
Number of gardens with ss. Maddenia collections
5 0 0 0 0 0 0 0 0 0
showed a similar pattern to the number of ex situ sites/coun- tries (Supplementary Fig. 1). However, taxa are generally not well conserved with wild accessions. Amongst the 18 threa- tened taxa, Rhododendron coxianum (1 wild accession), Rhododendron fleuryi (2), Rhododendron kiangsiense (1) and Rhododendron taronense (2) had fewer than three wild accessions, with none for Rhododendron roseatum and Rhododendron sinonuttallii. Although all four Near Threatened taxa had .10 wild accessions, the 12 Data Deficient taxa had few wild accessions in cultivation. Only four Data Deficient taxa were represented by more than three wild accessions. Notably, R. linearilobum and R. rhom- bifolium had no documented wild accessions, although they were in cultivation (Table 2; Supplementary Fig. 1). For the 20 Least Concern taxa, although little conservation con- cern is indicated, Rhododendron crenulatum, Rhododendron mianningense, Rhododendron parryae and Rhododendron pseudomaddenii had fewer than three wild accessions and two (Rhododendron vanderbiltianum and Rhododendron yungchangense) are not in cultivation. The two subspecies of the Rhododendron maddenii complex, R. maddenii subsp. maddenii and R. maddenii subsp. crassum, were re- presented by the greatest number of wild accessions.
Ecogeographical representation of ex situ collections
Using available provenance data (either coordinates or lo- cations), we mapped 179 of the 277 wild collections to show the geographical origins of ss. Maddenia in ex situ conservation (Fig. 1b; Supplementary Table 2). Most of the wild accessions were from south-west China, north-east India, Bhutan, eastern Nepal, northern Myanmar, north- ern Viet Nam and north-west Thailand. Amongst the taxa threatened or at risk (Critically Endangered, Endan- gered, Vulnerable, Near Threatened, Data Deficient), 10 (2 Critically Endangered, 2 Endangered, 3 Vulnerable, 3 Data Deficient) had documented wild accessions but from
Number of gardens with Rhododendron collections
16 0 0 0 1 0 0 1 0 1
Number of BGCI member gardens
40 1
10 1 1 7 0 1 0 3
Number of botanic gardens
173 5
138 10 1
18 2 1 5 5
fewer than three wild sources (Supplementary Fig. 2). Because of a lack of provenance data we did not map a pro- portion of wild collections (98/277, 35%; Supplementary Fig. 2; Supplementary Material 3). Although identified as from the wild, these collections were recorded with no geo- graphical information. This resulted in six taxa not being mapped (R. coxianum, R. kiangsiense, R. taronense, Rhodo- dendron levinei, R. parryae, R. pseudomaddenii) among the 49 taxa having recorded wild accessions in cultivation (Table 2).
Discussion
Ex situ conservation of Rhododendron subsection Maddenia
Our analysis of living collections will inform ex situ con- servation management of this subsection of 65 taxa to- wards the Global Strategy for Plant Conservation Target 8 (CBD, 2010). The 85% of ss. Maddenia taxa in cultivation is an improved position compared to the 73% for the whole genus in 2018 (MacKay et al., 2018), with all threa- tened taxa now cultivated in at least three sites (Supplementary Fig. 1a). This meets the Target’s criterion of ‘taxon cultivated in at least three ex situ sites and have at least three wild accessions’ to adequately capture genetic diversity in ex situ conservation. However, amongst the 34 taxa threatened or at risk, only two (Rhododendron excellens, Rhododendron nuttallii) are conserved with over 15 wild collections (number of wild sources in Sup- plementary Table 2; Supplementary Material 3), and half (17/34) do not meet the criterion (Supplementary Figs 1b & 2). In particular, six threatened taxa (R. coxianum, R. fleuryi, R. kiangsiense, R. roseatum, R. sinonuttallii, R. taronense; Supplementary Fig. 1b) have no or fewer than three wild accessions at any site. In addition, Data Deficient taxa account for 28%(18/65 taxa) of the whole
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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