566 T. M. H. Almeida et al.
climate change on cacti will go beyond physiology. Ecological factors, including dependence on pollinators and nurse plants, also play a key role in their survival (Reyes-García & Andrade, 2009; Goettsch et al., 2015). Some authors have suggested cacti are not vulnerable to the potential impacts of climate change (Larios et al., 2020), but others have emphasized the risks they face be- cause of low population growth rates (Shryock et al., 2014) and their limited natural ranges (Barthlott et al., 2015; Hultine et al., 2016), which could affect population regen- eration and success in reintroduction programmes (Carrillo-Angeles et al., 2016). The uncertainty that surrounds the potential impact of cli-
mate change on cactus diversity is a challenge for conserva- tion
planning.Nevertheless, the number of threatened species of Cactaceae is projected to rise, particularly in hotspots such as the Atlantic Forest and Caatinga, with up to 90%of species potentially threatened by 2050 (Pillet et al., 2022). Numerous globally threatened cacti, including Critically Endangered species, have not yet been secured in ex situ col- lections (Oldfield & Hunt, 2010). The Cactarium collection of the Rio de Janeiro Botanic Garden, established in 1913 (Brasil, 1914), has recently strengthened its contribution to ex situ conservation, including prioritizing species diver- sity, mapping in situ populations and conducting field surveys. This has resulted in an increase in the number of threatened species present in the collection from 11 in 2014 to 64 in 2019 (Gonzaga et al., 2019). Because of the importance of this collection, assessing its current holdings and planning future conservation actions
are vital to enable the Rio de Janeiro Botanic Garden to sup- port the effective conservation of cacti both in the wild and in cultivated collections. Here we evaluate the diversity of the collection and recommend strategic actions to enhance its conservation value.
Methods
The c. 3,000 m2 Cactarium of the Rio de Janeiro Botanic Garden (Gonzaga & Reis, 2019) is located in the Atlantic Forest and contains species of Cactaceae and other fam- ilies. Specimens are cultivated in three greenhouses, a pergola and external beds for public viewing, and two further greenhouses, a pergola for shade plants and a technical reserve area for research. Specimens for public viewing (Plate 1a–c) are planted in the ground and ar- ranged in groups for landscaping and educational pur- poses. Research specimens are maintained in vases (Plate 1d,e) for conservation and study. We inventoried all plants in this living collection during January–May 2022, counting all specimens and recording label data in a digital database. Specimens of Cactaceae were the most abundant in the collection, and identifications were confirmed by the curator of the Cactarium, who is a taxonomist specializing in this family. We consulted information on the inventoried plants in
the institutional specimen registry system, Jabot (Silva et al., 2017). We checked and updated scientific names, fol- lowing Flora e Funga do Brasil (2023) for native species, and the Tropicos database (Tropicos, 2023) and the Plants
PLATE 1 Rio de Janeiro Botanic Garden Cactarium, Brazil: (a) aerial view, (b) greenhouse for visitation, (c) outdoor flower beds, (d) pergola with the shade plant collection, (e) greenhouse for research. Photos: (a) A. Machado; (b–e) T.M.H. Almeida.
Oryx, 2024, 58(5), 565–575 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324000012
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