The best type of plant material to store in ex situ collections will vary by species. For species with ‘orthodox’ seeds (able to be dried and stored at low temperatures for many years and still remain viable), seed banks provide the greatest direct conservation value at the lowest cost. For species with ‘recalcitrant’ seeds (not able to be dried and stored), tissue culture or cryopreservation can provide high direct conservation value, but at a greater cost. Living plant collections can provide either direct or indirect conservation value, depending on how they are collected and maintained.
The type of ex situ collections maintained by different institutions will also depend on factors like the organization’s mission, availability of appropriate facilities, cultural conditions and climate, dedicated staff time and expertise, and financial support. Collaboration among institutions leads to more efficient and effective ex situ conservation action by pooling resources and connecting appropriate facilities, training, and other necessary support.
The protocols used to acquire plant material for ex situ collections determine the conservation uses and impacts of that collection. In general, well-documented, wild-collected ex situ collections that capture as much genetic diversity of the species as possible will have the greatest conservation value. Numerous organizations have developed protocols to guide the wild-collection of plant material for genetically diverse and appropriate ex situ collections for direct use in reintroduction projects. These protocols often focus on ex situ seed collections, as this is the most effective way to capture and store genetic diversity off-site over the long-term for species with orthodox seeds.
For example, the European Native Seed Conservation Network (ENSCONET) has produced manuals for seed collecting and curation which are avaialble in a wide range of languages (English, Spanish, French, Greek, German, Polish, Italian, Portuguese and Hungarian) and can be downlaoded here. Similarly, the Millennium Seed Bank (MSB) has developed a number of technical publications on seed banking which can be downloaded from the MSB website
Ex situ institutions such as botanic gardens often maintain collections of living plants represented by one to many specimens per species, and from sources that are of wild or non-wild (cultivated or unknown) origin. While only genetically diverse and representative collections are appropriate to directly support in situ conservation (e.g. reintroduction), living collections represented by only a few individuals from known sources serve important indirect conservation purposes, primarily through research, horticulture and education.
Collecting plant material for ex situ collections can impact the survival prospects of native populations if not carried out appropriately. Research has shown that collecting 10% of the seeds produced in a wild population once out of every 10 years does not significantly increase extinction risk, even for more sensitive species. However, collecting even slightly more than this can severely decrease survival prospects for some species (particularly those that are already experiencing population declines). This means ex situ collection efforts must be conducted carefully to ensure wild populations are not placed at additional risk. These findings highlight the importance of developing robust ex situ collections for species before their populations decline.
Finally, the long-term maintenance of viable and genetically diverse plant material plays a critical role in determining the ultimate conservation value of an ex situ collection. Without proper curatorial management, the conservation value of a collection, or the collection itself, can be entirely lost. Collections with the most direct conservation application are genetically diverse and representative of the species, and must be managed to ensure the material is genetically sound and available for research and conservation activities over the long-term. Many living collections today do not meet these standards due primarily to genetic issues such as having too little genetic diversity, being of unknown provenance, or losing genetic diversity via drift or adaptation to cultivation and hybridization.
Ex situ collections management should minimize the risk of loss due to random events or natural disasters (such as staff changeover, theft, fire, disease, or other catastrophic loss) by ensuring that collections are maintained at more than one site. Additionally, curatorial oversight of living collections through time is crucial to maintaining associations between collection data (e.g., provenance) and specimens. By using relational database and plant records technology, record-keeping for ex situ collections can ensure the maintenance of critical links between specimens and collection data for broader conservation and research activities.
To facilitate coordination and monitoring of this target, institutions with ex situ collections of wild plants (both living plant collections and seed banks) are encouraged to share data via BGCI's PlantSearch database. This database allows ready identification of rare and threatened plants in collections, facilitates collections-based research, as well as conservation priority setting through the identification of gaps in collections.