Trends in Plant Science
Volume 14, Issue 11, November 2009, Pages 590-598
Journal home page for Trends in Plant Science

Review
Special Issue: Plant science research in botanic gardens
Perspectives on orchid conservation in botanic gardens

https://doi.org/10.1016/j.tplants.2009.07.008Get rights and content

Orchids, one of the largest families of flowering plants, face an uncertain future through overexploitation, habitat loss and impacts of climate change. With their intricate abiotic and biotic dependencies, orchids typify the plight of global plant resources and, thus, provide ideal model species for ecological tracking and focussing conservation programs. Botanic gardens worldwide have traditionally been major centres of excellence in orchid horticulture, research and conservation as orchids generate wide public and educational appeal. Here, we highlight the role of botanic gardens in areas key to orchid conservation. With pristine habitats under threat globally, the challenge for orchid conservation programs will ultimately depend upon developing ecological restoration technologies, whereby orchids are reinstated into sustainably restored habitats.

Section snippets

Botanic gardens and conservation

As we face the sixth great extinction event, the question remains of what can be done to arrest the extinction crisis for plants [1]. With over 2500 sites worldwide (see: http://www.bgci.org/), botanic gardens represent the single largest biological institutional capacity, able to deliver effective plant conservation on all continents. But just how well are botanic gardens placed to meet the global extinction crisis? Are there models that demonstrate how to link ex situ conservation collections

Orchids as a scientific focus plant group in botanic gardens

With an estimated 25 000 species, orchids are the most species-rich of all angiosperm families [2]. They are found on all inhabited continents and are symbolic of the conservation crisis facing global plant life [3], with more orchid species listed as threatened on the International Union for Conservation of Nature (IUCN) Red List than species from any other plant family [4].

Threats to orchid populations include many of the major hazards facing plant life in general, such as overexploitation,

Pollination ecology

Since Darwin ignited world interest in orchid pollination [8], there is a growing body of literature showing how diversification of the family might be linked to pollinator specialization [9]. No other plant family engages in such an array of pollination syndromes. Rodents to birds, food rewards (oils to nectar), food and nest-site deception and a variety of mimicry systems ensure pollination success in orchids [10]. However, it is in the mechanism of sexual deception where orchids excel,

Mycorrhizal biology

Orchid-mycorrhizal biology has a long scientific history beginning in the 19th century, with several wide-ranging reviews of the biology, ecology and fungal associates of orchids (e.g. Refs 19, 20, 21). Whereas most orchids investigated have an association with fungi, only some studies demonstrate ecological specificity or the ecological reliance of the orchid for a fungal associate. The nature of this association, although historically considered mutualistic, has more recently been recognised

Conservation genetics

The past two decades have seen an increase in the use of molecular techniques in the field of orchid conservation, from protein studies (mostly alloenzymes) to DNA-based methods [amplified fragment length polymorphisms (AFLPs), microsatellites and DNA sequencing] [37]. Research groups in botanic gardens worldwide, often in collaboration with universities, have had a seminal role in the development of molecular approaches, with the Jodrell Laboratory at the RBG Kew representing a standout

Propagation

Outside of the large amateur interest in the propagation and culture of orchids, botanic gardens remain the major institutional organizations involved in orchid horticulture. The integration of scientific disciplines with practical horticulture found in many botanic gardens provides an ideal platform for combining knowledge acquisition with horticultural practice and presents exciting opportunities for botanic gardens to have a major role in translocation programs [7].

Unlike their epiphytic

Seed bank development

One characteristic of orchids that provides outstanding opportunities for conservation is their dust-like seed. A single seed capsule is capable of producing tens of thousands to millions of seeds [57], providing a ready and effective way to seed bank a species with as little as one seed capsule.

Despite the popularity of orchids, seed banking is in its infancy, with few empirical studies and a lack of general guiding principles, unlike the sophisticated approaches developed for seed banking of

Conservation priorities and education

Without doubt, the financial and time resources available to conserve biodiversity adequately are insufficient. Priority setting for conservation is usually focused on the conservation status of a species, or based on its evolutionary and taxonomic significance, with programs implemented often without analysis of the cost of management and likelihood of success [64]. Orchid conservation programs are no exception and often it is the most charismatic (e.g. the lady's slipper orchid project) or

Conclusion

The complexities of an orchid conservation program represent significant infrastructure and intellectual investment. Although relatively straightforward for epiphytic species, conservation of the one third of species that are terrestrial can represent significant technological challenges, as we move from species with low levels of biotic specialization and specificity to species with intricate and obligate ecological requirements. For some areas of specialization, such as mycorrhizal

Acknowledgements

The authors acknowledge the many colleagues and partner institutions who share our passion for conservation of orchids and who continue to marvel at these most beguiling of plants.

Glossary

Achlorophyllous
plants without chlorophyll.
Adaptive radiation
process in which one species gives rise to multiple species that exploit different niches.
Axenic culture
the culture of an organism that is entirely free from other contaminating organisms.
Epiphyte
a plant growing on another plant for mechanical support, although not parasitic, deriving its moisture and nutrients from the rain and air.
Genetic bottleneck
occurs when a portion of a population is either killed or prevented from reproducing

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