Essential to plant conservation practice of the Center for Plant Conservation is taking action that will benefit species’ survival and reduce the extinction risk of globally and/or regionally rare plant species. CPC participating institutions make conservation collections for this purpose. To maximize its value, a conservation collection has accurate records of provenance, differentiated maternal lines, and diverse genetic representation of the species. But how do you know the best way to capture a diverse genetic representation when collecting? And how can you maintain high genetic diversity in an ex situ collection? What is the best genetic composition for creating a new population? Below we provide guidelines based upon best available scientific evidence.
Genetic diversity is the basis for any species’ ability to cope with changes in its environment, including disease, stress, or extreme events. A mindset for gathering, maintaining, and using the maximum diversity possible drives the following recommendations (see Overview). Many recommendations ensure that in the absence of genetic data practitioners can collect and maintain the maximum level of genetic diversity. With more information obtained about a target species’ biology, ecology, and genetics, the more accurate genetic sampling and management will be. It is our hope that these guidelines will help practitioners make good decisions. For particularly small populations, the existing genetic diversity may be limited, therefore maximizing the diversity of the conservation collection and of the reintroduction or conservation translocation is very important.
Many factors affect genetic integrity of a conservation collection. Collectors who attempt to capture the breadth of genetic diversity represented within a population and the genetic diversity across populations will improve the likelihood of success for all conservation steps that follow. Nevertheless, collectors should be aware of the possibility that genetic erosion may occur over time in their collections and take steps to minimize it. While in storage, some maternal lines may survive better than others, hence diversity may be reduced. Similarly, when regenerating the seeds or tissues from storage, differential germination and/or survival is likely, hence diversity may be reduced. With attrition at all steps along the way, the number of individuals available for a reintroduction will likely be less than the original wild collection. Planning for these losses is an essential component for genetic management of your conservation collection (see Overview).
These updated guidelines incorporate research and experience of CPC conservation officers, previous CPC guidelines, Center for Plant Conservation Genetic Sampling Guidelines for Conservation Collections of Endangered Plants (Center for Plant Conservation 1991), and Revised Sampling Guidelines for Conservation Collections of Rare and Endangered Plants (Guerrant et al. 2004b), as well as current literature. Key research on the threats of inbreeding versus outbreeding depression and concerns about genetic rescue informed these guidelines (Frankham et al. 2011; Frankham 2015), as well as serious thought about how changing climate will influence rare plant populations (Havens et al. 2015, Vitt et al. 2016). New genetic techniques are revolutionizing our abilities to examine genetic links to ecology and evolution of species (Ellegren and Galtier 2016). These in turn may offer solutions to difficult problems rare plants face.
Questions to Ask
Before Acquiring a Conservation Collection
- Does collecting pose a threat to the wild population?
- What is the purpose of the collection? Note: These guidelines pertain to conservation collections. Depending on the purpose of the collection, sampling strategy and numbers can vary (Guerrant and Fiedler 2004; Guerrant et al. 2004).
- Can the ex situ collection be made such that it benefits the species’ survival and reduces extinction risk?
- How many estimated or known numbers of individuals and populations exist? (The sampling universe is known.)
- What is the breeding system?
- Is the taxon monoecious or dioecious?
- Is it self-compatible or self-incompatible?
- What is the propagule dispersal mechanism?
- In what types of habitats does the species grow?
- Should seeds or other tissues be collected? (See “Questions to Ask to Determine the Most Efficient Way to Preserve the Plant Tissue Long-Term.”)
- What is the storage capability of the taxon? Can the seeds be stored in a seed bank or will the other forms of ex situ specialized propagation and care be required?
- How long will material be stored?
- How can the plant material be propagated? Do you know the horticulture requirements for growing plants from seeds or cuttings?
- What level of attrition or mortality of collected material is expected in storage and regeneration? (See Guerrant and Fiedler 2004).
- Will the material be used for a reintroduction or conservation translocation?