Botanic gardens and the conservation of tree species

doi:10.1016/j.tplants.2009.08.013

Trends in Plant Science

Volume 14, Issue 11, November 2009, Pages 581-583

https://doi.org/10.1016/j.tplants.2009.08.013 Get rights and content

The general role of botanic gardens in plant conservation has been widely accepted since the 1970 s and many threatened plant species are now in well-documented living collections and seed banks. Conserving tree species in ex situ collections still presents particular challenges. Many trees have so-called ‘recalcitrant’ seeds that cannot be stored in conventional seed banks and the sheer size of living trees restricts the number of individuals of a particular species that can be grown in a botanic garden. Even if space is available, is ex situ conservation a desirable option and how does this compare with conserving tree species in their natural habitats? In reality, conservation action for globally threatened tree species, by either in situ or ex situ means, remains inadequate and steps should be taken to combine approaches to prevent the urgent loss of tree species worldwide.

Section snippets

The decline of tree species

Clearance of forest for agriculture and mining, logging for timber and overgrazing of woodlands have all contributed to the decline of tree species in the wild 1, 2, 3, 4, 5. Climate change is adding an additional overarching threat to species with limited distributions, such as trees that are endemic to the cloud forests of Mexico [6] and threatened trees that are endemic to Cuba [7]. Climate change is also likely to pose particular problems for tree species with poor regeneration and

Ex situ and In situ conservation of tree species

The Convention on Biological Diversity (CBD) defines ex situ conservation as the conservation of components of biological diversity outside their natural habitats (http://www.cbd.int/convention/convention.shtml). Ex situ conservation is the component of species conservation that is usually associated with zoos and botanic gardens. Article 9 of the CBD stresses the importance of ex situ conservation ‘predominantly for the purpose of complementing in situ measures’ (//www.cbd.int/convention/convention.shtml

Taking stock

At present, 1700 globally threatened tree species are recorded as represented in the living collections of botanic gardens and arboreta, according to the PlantSearch Database (http://www.bgci.org/plant_search.php) maintained by Botanic Gardens Conservation International (BGCI). Considering the 1002 Critically Endangered tree species, 192 are currently recorded in cultivation in the same database. An urgent priority is to ensure that all Critically Endangered tree species are included in ex situ

Conserving Magnolia spp.

Magnolias are one group of ornamental plants that are particularly well represented in botanic garden collections. Although the emphasis might be on showy cultivars, botanic gardens act as important repositories for globally threatened species of this genus. Over 130 Magnolia species are considered to be threatened with extinction, over half of all species in the genus [16]. As well as being valued ornamental trees and shrubs, magnolias also provide important sources of timber, medicinal

Restoration and reintroduction

Tree planting is widely seen as an important environmental activity and an effective response to climate change brought about by anthropogenic carbon emissions. However, knowledge of how to use tree species effectively in planting schemes is still inadequate. Generally, only a limited range of often non-indigenous tree species is used, particularly fast-growing species of pine and Eucalyptus. As pointed out by Innes and Hickey [17], forest plantations for carbon sequestration have generally

The last chance for trees?

Some of the trees represented in botanic gardens are already extinct in the wild including the Franklin tree, Franklinia alatamaha and Toromiro, Sophora toromiro. The specimens of these trees in botanic gardens around the world are poignant reminders of the loss of tree diversity in the wild. There is some hope that S. toromiro, the only tree on Rapa Nui (Easter Island) from which the iconic carvings were made, can be reintroduced to its island habitat [18] but as yet it remains only in ex situ

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Identifying gaps in the ex situ conservation of native plant diversity in China
2023, Biological Conservation
Due to intensified human pressure and climate change, ex situ conservation measures have become essential for conserving Earth's remaining biodiversity, but the development of targeted ex situ conservation strategies based on conservation gaps analysis is often a major challenge. Here, we used a dated phylogeny including 95.70 % of the Chinese vascular genera and 1,540,695 species distribution records to identify ex situ conservation gaps in the tree of life and geographic space in China. We found that at least 41.70 % (12,716 species) of all vascular plant species (30,494 species), including 49.31 % (1715 species) of Chinese endangered species, are conserved in the botanic gardens. The results show that most species in ex situ collections are from eastern China and have been housed in botanic gardens in this region, whereas several plant diversity hotpots in the southwestern and northwestern regions are not well represented in ex situ conservation; only 12.67 % of the collection capacity of the Chinese botanic gardens is allocated to endangered species; there are 18 phylogenetic clusters of genera absent from the ex situ collections and the missing species are mostly from alpine or desert, mainly distributed in the Himalaya-Hengduan Mountains and northern Xinjiang. Therefore, we suggest that more collection capacity of China be devoted to endangered species particularly in the southwestern and northwestern regions. Our study provides quantified resources of targeted inventory and area for future ex situ conservation in China, and a fundamental protocol to invest the future achievement of local or global ex situ conservation.
Ex situ species conservation: Predicting plant survival in botanic gardens based on climatic provenance
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Citation Excerpt :
Ex situ plant collections play an increasingly important role in biodiversity conservation amid growing anthropogenic pressures (Oldfield, 2009; Smith and Pence, 2017), including overharvesting, habitat alteration and climate change (Lughadha et al., 2020).
Living collections grown in outdoor landscapes within botanic gardens play an increasingly important role in ex situ species conservation, but there is little work predicting the survival of different plant species in these landscapes. Here we present an approach to predict the survival of plants grown from wild propagules in botanic gardens, based on climatic provenance. We developed mixed effects Cox models to relate plant survival to horticulturally informed measures of climatic differences between botanic garden landscapes and the wild distribution of plants. We fit these models to data on the survival of 1184 plantings of 410 species grown in the Missouri Botanical Garden (MBG, in Saint Louis, Missouri, USA) from wild propagules collected around the world. We detected major effects of growth form, minimum temperature of the coldest month, maximum temperature of the warmest month, and to a lesser extent precipitation of the driest month. Survival at MBG was predicted better by the climate of propagule collection localities than by the overall climatic distribution of species, suggesting local adaptation. However, there was substantial interspecific variation in survival among plants from similar climates. The best models predicted high survival for plants grown at MBG from propagules collected within broad latitudinal bands across non-tropical regions. We explore implications of these findings for the role of botanic gardens in ex situ conservation, and discuss the applicability of the approach we developed to enhance the capacity of living collections to represent species of conservation concern.
Proportional sampling strategy often captures more genetic diversity when population sizes vary
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Collecting and conserving genetic diversity from plant populations for ex situ collections is a major objective of seed banks and botanic gardens. However, current guidelines for collecting germplasm to preserve plant species ex situ might not adequately capture the genetic diversity present in real plant population systems. Here, we tested a previously unexplored challenge for sampling practices: when populations of a rare plant species vary in size. We hypothesized that sampling proportional to the population size would capture more genetic diversity than sampling an equal number of individuals from every population. Using simulations of a hypothetical rare species, we tested equal and proportional strategies and calculated how many alleles were captured by either strategy. The effects of migration rate, recent bottlenecks, and sampling intensity on genetic diversity capture were also examined. We found that when population sizes differ (e.g., one population 3 times the size of median population size), proportional sampling captures more genetic diversity under constant size populations. The relatively modest improvement (1–5% more allelic diversity for most cases) was observed across all parameters of migration and intensity tested–except when there were recent bottlenecks. We also created simulations tailored to three IUCN Red List threatened oaks (Quercus oglethorpensis, Q. engelmanii, and Q. acerifolia) and found similar results for these detailed case studies as for our generic simulations. We conclude that sampling proportional to population size may often be a useful sampling strategy to create genetically diverse ex situ plant populations, ultimately resulting in more efficient use of resources.
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Citation Excerpt :
However, habitat loss caused by climate change, land degradation, habitat fragmentation, or biological invasion (Thuiller et al., 2005; Conser and Connor, 2009; Gibbs and Salmon, 2015; Haddad et al., 2015) complicates the preservation of plants in situ. Ex-situ conservation has become an effective strategy for vegetation restoration (Hawkins et al., 2008), because it not only ensures the survival of plants, but also increases the number of ex-situ collections and provides materials for future reintroduction (Oldfield, 2009; Mounce et al., 2017). One of the main aims of the Global Strategy for Plant Conservation is to conserve 75% of threatened plant species in ex-situ collections, of which at least 20% is to be used for restoration activities (SCBD, 2010; Sharrock, 2012).
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Trends in Plant Science

UpdateFORUM: Science & SocietyBotanic gardens and the conservation of tree species

Section snippets

The decline of tree species

Ex situ and In situ conservation of tree species

Taking stock

Conserving Magnolia spp.

Restoration and reintroduction

The last chance for trees?

Diversity in strategies for conifer conservation, the Action Plan and future developments

Acta Hortic.

The Red list of Endemic Trees and Shrubs of Ethiopia and Eritrea

The Red List of Trees of Guatemala

The Red List of Trees of Central Asia

Conservation of tree species through sustainable use: how can it be achieved in practice?

Oryx

Applying climatically associated species to the modelling of compositional change in tropical montane forests

Global Ecol. Biogeogr.

Plants and Climate Change: Which Future?

Red Listing the world's tree species: a review of recent progress

Endanger. Species Res.

Update
FORUM: Science & Society
Botanic gardens and the conservation of tree species