Complementary ex situ conservation actions


A complementary conservation strategy involves the combination of different conservation actions (in situ and ex situ), which together lead to an optimum sustainable use of genetic diversity existing in a target genepool.

Source - Dulloo, M.E., Ramanatha Rao V., Engelmann F. and Engels J.. 2005. Complementary conservation of coconuts. In P. Batugal, V.R. Rao and J. Oliver, (eds.) Coconut Genetic Resources. IPGRI-APO, Serdang. Pp. 75-90.

Though it is essential to maintain species’ evolution and promote diversity through natural selection processes, in situ conservation has significant limitations. It is therefore important to complement in situ conservation activities with ex situ actions (in genebanks or botanic gardens) in order to ensure the maximum genetic diversity of target species is safely conserved.

This module compares ex situ and in situ conservation and present a number of different ex situ conservation methods.

In situ versus ex situ conservation

In situ conservation allows evolution and enhancement to continue through exposure to pest, diseases and other environmental factors whilst contributing to indirect benefits, including ecosystem support. Still it requires extensive areas for effective conservation which are expensive to maintain and might lead to conflicts with local landowners.

Ex situ conservation requires only limited space, is more cost effective and conserves an adequate representative sample of CWR populations. Nonetheless it is difficult to ensure adequate sampling (intra-specific variability) and ex situ conservation freezes the evolutionary process.

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Ex situ conservation methods

Seed genebanks
Involves drying seeds to low moisture content and storing them in moisture-proof containers at a low temperature.

Field genebanks
Consists of growing live plants in a field or in a screen or greenhouse. This method offers easy access to plant material for characterization, evaluation and subsequent utilization, but is often difficult and expensive to maintain.

Tissue culture
Involves the maintenance of plants in a sterile, pathogen-free environment with a synthetic nutrient medium.

Involves the storage of a range living tissues, including cell suspension, calluses, shoot tips, embryos and even whole seeds, at extremely low temperatures in liquid nitrogen.

Pollen storage
Pollen can be stored in the same way as seeds and used as a conservation method for genetic resources, especially for perennial species of fruit and forest trees.

Botanic Gardens
Involves the maintenance of live plants in a garden landscape. Since botanic gardens have limited amounts of space, the number of accessions of individual species is limited and thus their value for genetic diversity conservation is often questioned.

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Using ex situ collections to save CWR populations

Ex situ collections may be used to re-introduce a species that has disappeared from its natural environment. Accessions collected in the past and conserved in genebanks or in botanic gardens can provide valuable materials for restoration. The re-introduction of ex situ materials to the wild is a complex activity and needs to undertaken with careful consideration. One must ensure the stock or accessions introduced are, in fact, native to the site, that plants are free of diseases and that they have adequate genetic diversity.

Ex situ collections may also be used in enrichment planting or re-enforcement for threatened CWR populations and those which are not regenerating in the wild. New plant material can be obtained from ex situ collections and planted to reinforce the population at the site.

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