- Maintaining small populations of plants in protected places may be a necessary conservation strategy for some species; these are known as field genebanks. At botanical gardens, these are often part of living display collections.
- The genetic diversity of the field genebank requires awareness of maternal line health and representation over years in cultivation and may require intentional gene flow via cross-fertilization from wild populations or from sister institutions housing the species.
- Institutional collaborations and careful georeferenced record keeping and sharing will be essential for maximizing conservation value of field genebanks.
Some rare species whose seeds cannot be stored by conventional means or do not produce seeds (exceptional species; Pence 2014) will need to be maintained as whole plants growing in a group or population on property that can offer long-term security. Field genebanks have been traditionally developed for cultivars of com-mercially valuable plants that must be maintained as living clones (FAO 2013). Within the CPC network, field genebanks, sometimes called living collections, are grown at our botanical gardens or on properties where landowners have agreed to con-serve and maintain living populations of the species for many years. When the field genebank is located near a water source and fenced so that plants are protected from herbivory, it improves the ability to care for the collection and the chances of the collection’s long-term survival. Most CPC field genebanks support long-lived tree species with five to 20 unrelated individual plants per conservation collection. Most require collaborations across institutions, because it is unlikely that a single institu-tion will have enough space available to house the 100 or more individuals needed to capture the desired genetic diversity of a species.
In Hawai’i, special field genebanks have been established and are known as inter situ collections. They are, in a sense, half-way houses between the full care facilities of-fered at a botanical garden and the “fend for oneself” life in the wild. Often located at mid-elevation between the plant’s wild habitat (which in many cases can no longer support the species) and the practitioner’s botanical garden, these semi-protected settings provide a place where plants can experience some natural climatic variation, while still receiving supplemental care when necessary.
Field genebanks require very long-term planning and commitment by property owners. Plants have the best of both worlds: exposure to some natural climatic conditions and extra help (usually in the form of water, fertilizer or hand-pollination) when necessary. This can help ensure maintenance of adaptive traits; support of mutualists like pollinators, seed dispersers, and soil microorganisms; and easy access to propagules for restoration.
Acquiring a Conservation Collection for Field Genebanks or Inter Situ Collection
Make preparations before making collections.
- Plan the conservation collection considering species' attributes and institutional capacity. (See “Questions to Ask before Acquiring a Conservation Collection” box and “Hierarchy of Questions to Ask to Determine the Most Efficient Way to Preserve the Plant Tissue Long-Term” box).
- Know how to identify the species and know its natural and cultural history. Consult with local botanical experts and agency recovery staff. Work with in-country partners to make collections. By acquiring data on the species’ phenology at the target population site, you may streamline your collection trips. Visit publicly available plant collections databases, such as the Global Biodiversity Information Facility (GBIF), to determine the time of year a species typically produces flowers or fruits. Explore citizen science projects, such as iNaturalist, to view georeferenced photos of plant observations in real time. Take a reconnaissance trip to verify the actual timing of flowering and fruit set so that you can capture seeds when they are ripe. Recording flowering date and maturity of seeds in the population can aid future collections and can be reported with accession information. (See Example Monitoring Form.)
- Understand legal obligations for collection, transport, and propagation. Obtain permission from landowners to make seed collections and report permit numbers in accession records. Realize that obtaining permits for listed species may require obtaining permits from landowners and regulatory state and federal agencies; the process may take as long as 6 months to 1 year, so it is important to begin the process well in advance of your collecting season. FAQ - How can I obtain permits to make seed collections?
- Know sources for gathering reliable information about species’ conservation status. FAQ - How can I find out a species conservation status?
- Research the seed storage requirements of a taxon, as this will determine how the seed will need to be processed after collection. FAQ - How do I know my species storage requirements?
- To avoid over collection and/or to learn from other collectors, survey other ex situ collections to determine what species and populations have already been collected. For example, check records in Plant Search for Botanic Gardens Conservation International or California Plant Rescue.
- Participating Institutions can search for priority species for their region in the CPC PI portal on the “Rare Plant Finder” tab.
- Become familiar with Sentinel Plant Network and Weed Risk Assessments. Evaluate potential pest/pathogen issues and invasive behavior of the species you are collecting (Gordon and Gantz 2008; Gordon et al. 2008a and 2008b; Reichard et al. 2012).
While collecting, do no harm to collecting site or the rare plant population.
- If no previous specimen exists for the species at your collecting site or if the last known specimen is more than 10 years old and the population is large enough to accommodate removing one plant or plant part, document the identification of the species with a voucher specimen. If the population is not large enough, take good photographs. Note that permission to collect the voucher may be required prior to the collection.
- Collect within permit guidelines. To minimize impact on the wild population, collect no more than 10% (or the maximum allowed by permits) of an individual plant’s reproductive output and/or no more than 10% of the population reproductive out-put in a season (Menges et al. 2004). For many species making collections at this intensity can be sustainable over multiple years, but the intensity and frequency of safe collection is influenced by population and climate specifics. For species that will need to be maintained in a field gene bank, consider the total number of plants your institution and partner institutions could maintain so that you avoid over-collecting. (See Part 1B, “Collecting Seeds from Wild Rare Plant Populations” and Part 3B, “CPC Genetic Guidelines for Acquiring a Conservation Collection.”)
- Adhere to highest outdoor standards. Leave only footprints. Some habitats are extremely fragile. Adjust actions accordingly, including being mindful of habitats that are particularly sensitive to trampling and erosion.
- Be aware of any sensitive animal species at your sites. Access may require permits, training, or adjusted timelines if protected animal species co-occur with or near your species of interest.
Capture representative genetic diversity.
- Collect within permit and institutional space constraints.
- Capture representative genetic diversity across the population’s spatial expanse, morphological maternal plants and range of seed appearance. Include seeds or tissues from large and small maternal plants, along the edge and from the center of the population. It is also good to sample across years to capture diversity. Some populations have individuals that flower sporadically due to varying environmental conditions (Namoff et al. 2010, Griffith et al. 2015). Collecting in a single year will not capture total population genetic diversity. For the same reason, it is important to collect from early seeding, mid-season, and late seeding individuals within a year. This requires returning at multiple times to the population.
- For seeds, strive to collect mature seeds. If you detect immature seeds in your collection, attempt to germinate immediately.
- For stem cuttings, attempt to collect multiple replicates per maternal line of tissues at appropriate developmental stage for traditional vegetative propagation and tissue culture (that is, not excessively woody).
If possible, pair the collection with parallel leaf samples for DNA banking. Within the database, maintain linked genetic information with the plant growing in the collection.
Genetic studies can help determine the number of plants needed to capture the majority of a wild population’s genetic diversity. (See Figure 2.4 /3.2 in Griffith et al. 2015; see Hoban and Strand 2015; Hoban and Schlarbaum 2014 and Kashimshetty et al. 2017 for simulation studies related to efficient sampling).
Transport to propagation facility in the shortest time possible and in the best condition possible.
- Document the collection appropriately.
- Essential accession information includes: institution name, accessionnumber, collector, collection date, species name, family, locality information, georeferenced latitude and longitude, site ownership, permit documentation, and population information (the total number of individuals in the population, number of reproductive individuals, and number of individuals sampled for seeds that were harvested). (See CPC Field Collection Form.)
- Providing habitat information may provide clues to germination or tissue culture requirements of the species. Recommended fields include light and moisture conditions, soil type, slope orientation, and associated species. Provide photos of habitat and plant in its habitat.
- Be sure to document any associated collections (for example, leaf litter, soil, mycorrhizal fungi) and maintain the link through processing of samples.
- Gather and report additional accession data according to institutional protocols. Complying with International Transfer Format for Botanic Garden Plant Records and/or Darwin Core standards will allow easy transfer of information to partners.
Complete one field form per accession. Multiple accession numbers and field forms only need to be created for collections made from populations, which are differentiated by at least 1 kilometer.
Transmit accession data to CPC.
Maintaining the Field Genebank or Inter Situ Conservation Collection
At the propagation facility, follow steps for material type to propagate and maximize its survival.
Optimize conservation value.
- For highest conservation value, maintain adequate numbers of plants to allow for long-term sustainability of the collection and ability for plants within the collection to reproduce to provide material for other conservation uses.
- Realize that adequate numbers of 100+ individuals may require collaborations with other institutions.
Georeference the collection and label plants clearly.
- Use georeferencing to label collections.
- Replace labels with accession numbers as the collection ages.
Use appropriate cultivation practices to provide optimal conditions for growth and reproduction.
Monitor collection health; minimize weeds and pests.
Minimize artificial selection and genetic drift.
- While growing the conservation collection in the nursery, garden, or inter situ setting, minimize artificial selection and genetic drift.
- If an accession must be maintained as whole plants for a number of generations, maintain as large a population as possible and provide periodic immigration of approximately five migrants per generation from a wild source population or a sister institution housing the species and increase (triple, if possible) the samplesize each generation (Havens et al. 2004).
Consciously maintain high genetic diversity of the collection.
- Maintain identities and numbers of maternal lines to capture diverse growth rates, flower production, and presumably genetic diversity. If plants die, take care to propagate new plants to maintain the number of maternal lines represented in the conservation collection.
- Accurate documentation in the database and on individual plants is key to accomplish this.
Minimize unintended hybridization.
- Maintain accessions of conspecifics from different populations or congenerics separated at distances that will minimize unintended hybridization. If you plan to collect seed in a given year, bag flowers and hand-pollinate or clip flowers of conspecifics from different populations or congenetics that year, as gardens might not be big enough for spatial isolation.
Document the horticultural care and conservation management given the collection.
Maintain the value of the collections.
- Realize that institutional memory is key to maintaining the value of these collections, as the individual plant lives may be longer than the average tenure of personnel working at the institution. For any record, imagine that someone 50 years hence will need to read and understand exactly what you did.
Capturing Material for Future Conservation Uses
Collaborate with sister institutions.
- Collaborate with sister institutions housing the species to maximize next generation reproduction (Fant et al. 2016)
- Inventory ex situ collections of sister institutions holding the species.
- If possible, conduct genetic studies to compare captive to wild population genetic diversity.
- It may be necessary to transport pollen from wild population or a sister institution for hand-pollination trials. If genetic fingerprints or ancestries are known, then compatible matches can ensue to optimize genetic diversity of next generation as is done with endangered animals (Princée 2016).
Collect seeds of the next generation when they develop.
- If possible, store via cryopreservation or distribute seeds to sister institution with interest in long-term preservation of the species. Maintain records of maternal line, dates of seed production, and storage details in database. See Part 2B, “Collecting and Maintaining Exceptional Species in Tissue Culture and Cryopreservation.”
Use next generation material for reintroductions or conservation translocations.
- When opportunities arise, use next generation material for reintroductions or conservation translocations. See Part 4, “Rare Plant Reintroduction and other Conservation Translocations.”
Reference for CPC Guidelines
FAO Genebank Standards for Plant Genetic Diversity (FAO 2014)
Standards for Acquisition of Germplasm
5.2.1 All germplasm accessions added to the genebank should be legally acquired, with relevant technical documentation.
5.2.2 All material should be accompanied by at least a minimum of associated data as detailed in the FAO/Bioversity multi-crop passport descriptors.
5.2.3 Propagating material should be collected from healthy growing plants whenever possible, and at an adequate maturity stage to be suitable for propagation.
5.2.4 The period between collecting, shipping and processing and then transferring to the field genebank should be as short as possible to prevent loss and deterioration of the material.
5.2.5 Samples acquired from other countries or regions within the country should pass through the relevant quarantine process and meet the associated requirements before being incorporated into the field collection.
Standards for Establishment of Field Collections
5.3.1 A sufficient number of plants should be maintained to capture the genetic diversity within the accession and to ensure the safety of the accession.
5.3.2 A field genebank should have a clear map showing the exact location of each accession in the plot.
5.3.3 The appropriate cultivation practices should be followed taking into account micro-environment, planting time, rootstock, watering regime, pest, disease and weed control.
Standards for Field Management
5.4.1 Plants and soil should be regularly monitored for pests and diseases.
5.4.2 Appropriate cultivation practices such as fertilization, irrigation, pruning, trellising, rootstock and weeding should be performed to ensure satisfactory plant growth.
5.4.3 The genetic identity of each accession should be monitored by ensuring proper isolation of accessions wherever appropriate, avoiding inter-growth of accessions, proper labelling and field maps and periodic assessment of identity using morphological or molecular techniques.
Standards for Regeneration and Propagation
5.5.1 Each accession in the field collection should be regenerated when the vigour and/or plant numbers have declined to critical levels in order to bring them to original levels and ensure the diversity and genetic integrity is maintained.
5.5.2 True-to-type healthy plant material should be used for propagation.
5.5.3 Information regarding plant regeneration cycles and procedures including the date, authenticity of accessions, labels and location maps should be properly documented and included in the genebank information system.
Fant, J. B., K. Havens, A. T. Kramer, S. K. Walsh, T. Callicrate, R., C. Lacy,M. Maunder, A. Hird Meyer, and P. P. Smith. 2016. What to do when we can’t bank on seeds: what botanic gardens can learn from the zoo community about conserving plants in living collections. American Journal of Botany 103 (9): 1541–1543.
Gordon D., and C. Gantz. 2008. Screening new plant introductions for potential invasiveness: a test of impacts for the United States. Conservation Letters 1:227–235.
Gordon, D. R, D. A. Onderdonk, A. M. Fox, and R. K. Stocker. 2008a. Consistent accuracy of the Australian weed risk assessment system across varied geographies. Diversity and Distribution 14:234–242.
Gordon, D. R, D. A. Onderdonk, A. M. Fox, R. K. Stocker, and C. Gantz. 2008b. Predicting invasive plants in Florida using the Australian weed risk assessment. Invasive Plant Science and Management 1:176–195.
Griffith, M. P., M. Calonje, A. W. Meerow, F. Tut, A. T. Kramer, A. Hird, T. M. Magellan, and C. E. Husby. 2015. Can a botanic garden cycad collection capture the genetic diversity in a wild population? International Journal of Plant Sciences 176: 1–10.
Guerrant, E. O. Jr., K. Havens, and M. Maunder. 2004. Ex situ plant conservation: supporting species survival in the wild. Island Press, Washington, DC.
Havens, K., E. O. Guerrant, Jr., M. Maunder, and P. Vitt. 2004. Guidelines for ex situ conservation collection management. Pages 454–473 in Guerrant, E. O., Jr., K. Havens, and M. Maunder, editors. 2004. Ex situ plant conservation: supporting species survival in the wild. Island Press, Washington, DC.
Hoban, S., and A. Strand. 2015. Ex situ seed collections will benefit from considering spatial sampling design and species’ reproductive biology. Biological Conservation 187:181–191.
Hoban, S., and S. Schlarbaum. 2014. Optimal sampling of seeds from plant populations for ex situ conservation of genetic biodiversity, considering realistic population structure. Biological Conservation 177:90–99.
Kashimshetty, Y., S. Pelikan, and S. H. Rogstad. 2017. Effective seed harvesting strategies for the ex situ genetic diversityconservation of rare tropical tree populations. Biodiversity and Conservation 26: 1311–1331.
Meissen, J. C., S. M. Galatowitsch, and M. W. Cornett. 2017. Assessing long-term risks of prairie seed harvest: what is the role of life-history? Botany 95: 1081–1092, https://doi.org/10.1139/cjb-2017-0069.
Menges, E. S., E. O. Guerrant, Jr., and S. Hamze. 2004. Effects of seed collection on the extinction risk of perennial plants. Pages 305–324 in E. O. Guerrant, Jr., K. Havens, and M. Maunder, editors. Ex situ plant conservation: supporting species survival in the wild. Island Press, Washington, DC.
Namoff, S., C.E. Husby, J. Francisco-Ortega, L.R. Noblick, C.E. Lewis, and M. P. Griffith. 2010. How well does a botanical garden collection of a rare palm capture the genetic variation in a wild population? Biological Conservation 143: 1110-1117
Pence, V. C. 2014. Tissue cryopreservation for plant conservation: potential and challenges. International Journal of Plant Sciences 175: 40–45.
Princée, F.P.G. 2016. Exploring Studbooks for Wildlife Management and Conservation. Springer, Cham, Switzerland.
Reichard, S., H. Liu, and C. Husby. 2012. Managed relocation of rare plants another pathway for biological invasions. Pages 243–262 in J. Maschinski and K. E. Haskins, editors. Plant reintroduction in a changing climate: promises and perils. Island Press, Washington, DC.