Plants for the future – a future for our planet.
Volume 9 Number 1 - January 2012
Marie-Stéphanie Samain and Eduardo Cires
It is estimated that one-third of all plant species are threatened with extinction and yet plants continue to be under-represented in conservation debates and policies. However, global initiatives, such as the Global Strategy for Plant Conservation (GSPC) are aiming to bring a significant change. As stated in Target 8 of the GSPC, at least 75% of threatened plant species should be present in ex situ collections. Botanical gardens play a key role in conservation of plant diversity, but about only 30% of globally threatened plant species are currently held in their living collections (Oldfield, 2010). To be of conservation value, living collections must be genetically representative. Although information on genetic diversity in ex situ collections is scarce, it is thought that diversity is low in collections of numerous species. Moreover, besides the many studies and initiatives for specific taxa, our knowledge about the genetic diversity of threatened plant species in general is quite limited. This lack of insight into genetic diversity of threatened wild plant species contrasts with the broad knowledge about crops and their wild relatives. This fact is also reflected by GSPC Target 9, which specifically states that 70% of the genetic diversity of crops, including their wild relatives and other socio-economically valuable plant species, should be conserved. We still have a long way to go to understanding genetic diversity in threatened plants, conserving an important part of this diversity in ex situ collections, defining which percentage of genetic diversity might be feasible and/or desirable to aim for, and finally making this available for conservation and restoration projects.
Setting the stage
The GSPC 2011-2020 states that:
“Without plants there is no life. The functioning of the planet, and our survival, depends upon plants.”
Achieving Target 8 of the GSPC depends on the existence of genetically representative collections, and these are essential for recovery and restoration work. Our focus should therefore be on assessing and ensuring the conservation value of ex situ collections (Sharrock et al., 2010).
Assessments of a representative sample of plant species will provide a basis for an initial estimation of a baseline, and to monitor progress towards this target. Therefore, toolkits under this target need to include protocols for genetic management of ex situ collections and consequent reintroductions.
One of the suggested milestones to serve as a step towards the 2020 target is that ex situ collections of all critically endangered species should be genetically representative of the species (SBSTTA, 2010). However, preliminary observations and data suggest that this currently is not the case in many collections, as the genetic diversity from wild population to ex situ collections ‘gradually’ decreases (= genetic bottleneck) as a consequence of 1) habitat destruction narrowing genetic diversity and subsequent evolution (= genetic erosion), 2) collection bias (‘easy’ localities, selection of morphological variation which is not necessarily reflected by genetic variation), 3) cultivation bottleneck (accessions dying because of unsuitable conditions). Hence, the establishment of a protocol guiding genetic management during the different steps (wild population – ex situ collection – reintroduction) is essential for implementation of Target 8 of the GSPC and, ultimately, for safeguarding the future of our planet.
Towards an assessment for flagship groups: Hydrangea, Magnolia and Cactaceae
The Botanical Garden and the Research Group Spermatophytes of Ghent University (Belgium) are increasingly involved in conservation of the plant groups which are housed in their living collections and studied in ongoing projects, such as Peperomia (Samain et al., 2010), Hydrangea (Red List project in cooperation with BGCI, including a specific conservation project in Mexico), and Aristolochia (Rivera Hernández & Samain, 2011). Our strategy, to combine fundamental botanical research with conservational efforts, has also led to the establishment of a project, initiated in 2011, which will be continued and accelerated thanks to the support of the Fondation Franklinia. Within this project we aim to compare genetic diversity between wild populations and ex situ collections of three unrelated Angiosperm groups with different life histories and growth forms. A range of genomic tools will be applied to wild and ex situ individuals of selected species of the flagship groups Hydrangea, Magnolia and Cactaceae to enable rapid characterization of genetic variation, providing 1) support for specific conservation actions, and 2) general guidelines and a protocol on genetic management for acquiring accessions for ex situ collections, in order to be used by collectors and botanical gardens worldwide in the framework of achievement Target 8 of the GSPC.
Sampling and lab work
The three plant groups being studied are considered as priority groups for BGCI, the IUCN/SSC Global Trees Specialist Group and the International Organization for Succulent Plant Study (IOS), with whom we cooperate. These groups are rather well-studied taxonomically and are also very important in the horticultural trade, with especially Cactaceae also suffering from illegal harvest and trade. Despite the fact that these groups are a priority for conservation, the genetic diversity within ex situ collections is almost entirely unknown, and has not been compared with wild populations. There is clearly an urgent need for this research.
“Around one-third of the globally threatened species that are found in botanic garden collections are recorded in only one collection.”
Global and/or local Red Lists are available for each group (Magnolia: Cicuzza et al., 2007; Cactaceae: e.g. IUCN, 2011) or are being prepared (Hydrangea s.l.). These groups represent different unrelated families of Angiosperms, with different habitat preferences and a range of life history traits. Within each group, taxa are selected based on: 1) presence in a representative number of public and accessible private ex situ collections (botanical gardens, arboreta, etc.), 2) well-documented origin of the accessions, and 3) availability of material verified by specialists. Because of the second criterion, the quantity of useful accessions is much reduced, but we believe it is not useful to include samples without documented origin as their value, for example in reintroduction projects, is highly doubtful. Additionally, Magnolia and Hydrangea individuals are plants with life spans of several hundred years, predating fragmentation events, so we will obtain reliable genetic information that may help genetic restoration projects (e.g. López et al., 2008).
Availability in botanical garden collections has been checked via the PlantSearch module on the BGCI-website (http://www.bgci.org/plant_search.php) or via direct and ongoing communication with gardens. A final selection criterion is that most of the species are ‘Vulnerable’, ‘Endangered’ or ‘Critically Endangered’ according to IUCN Red List categories and criteria, hence they are priority species for conservation and for use in recovery and restoration work. Furthermore, the genetic diversity of these rare species will be compared with some more common or widespread species.
Field work has already been or will be performed in countries and areas where the Research Group has extensive field experience and local cooperation partners (Latin America and East Asia). Within the wild populations, a representative sample of individuals will be collected, meanwhile in the ex situ collections we aim to include an equal number of accessions from as many gardens as possible. In addition, our work on Hydrangea will also help to build new living collections, e.g. in Mexico, supported by the Mohamed Bin Zayed Species Conservation Fund.
Molecular tools provide valuable data on diversity through their ability to detect variation at the DNA level. Identification is of fundamental importance in diversity studies in a variety of different ways. For evaluation of species diversity, it is essential that individuals can be classified accurately. The identification of taxonomic units and endangered species, whose genetic constitution is distinct from their more abundant relatives, is important in the development of appropriate conservation strategies. Taking advantage of current molecular techniques, relatively quick assessments of genetic diversity in plants can be performed using well-sampled material and ready-made protocols, as long as the most limiting factor, funding, is available. For each flagship species, different molecular techniques (e.g. RFLP, microsatellites, AFLP, ISSR, PCR sequencing) are currently being tested and/or developed, with comparisons of cost versus data yielded, ease of use, and applicability for conservation research (Table 1). For the elaboration of these techniques, either in-house experience has been developed or collaboration with experienced research groups has been set up.
Table 1. Comparative assessment of some of the salient characteristics of different molecular genetic screening techniques: RFLP (or Restriction fragment length polymorphism), Microsatellites or simple sequence repeats (SSRs), AFLP (or Amplified fragment length polymorphism), ISSR (or Inter Simple Sequence Repeat) and PCR sequencing.
Outlook – Connecting the dots
To our knowledge, this is the first comprehensive study of this kind, with a constant evaluation of the different techniques, in order to assess the progress of the project (see Figure 1).The expected results can be subdivided in two levels: i) specific results for each group: they will provide insight into genetic diversity and history, providing a basis for further conservation work; ii) comparison of different unrelated groups with different life histories and growth forms: this approach will lead to a general overview of the genetic diversity available in wild populations and ex situ collections, as well as of the specific problems involved with decreasing genetic diversity from the wild to the collection, information which will be extremely useful for implementation of Target 8 of the GSPC.
Some important specific outcomes are listed here: 1) assessment of percentage of genetic diversity present in ex situ collections worldwide for the three plant groups under study, 2) identification of priority populations for ex situ conservation, 3) definition of a genetically representative collection (compared to Target 9 of the GSPC stating that 70% of the genetic diversity of crops and other socio-economical valuable plant species should be conserved), 4) indication of the number of samples that needs to be collected in the wild to obtain a genetically representative collection, 5) testing the hypothesis that endangered species with narrow distribution are genetically limited, 6) conservation of flagship species, and finally, 7) reports and publications in cooperation with e.g. BGCI, the IUCN/SSC Global Trees Specialist Group and the IOS.
Last but not least, it has already become clear during this pilot year 2011 that this study will lead to further international cooperation with many interested gardens and researchers.
“We expect to form a scientific network studying genetic diversity in plants for conservation purposes under the auspices of BGCI.”
Please feel free to contact us if you would like to cooperate, exchange experiences, or if you do have comments or questions.
Cicuzza, D., Newton, A. and Oldfield, S. 2007. The red list of Magnoliaceae. Fauna & Flora International. Cambridge, UK.
IUCN, 2011. IUCN red list of threatened species. http://www.iucnredlist.org/ (Accessed January 2012).
López, D.M., Bock, B.C. and Bedoya, G. 2008. Genetic structure in remnant populations of an endangered Andean Magnolia. Biotropica 40: 375-379.
Oldfield, S. 2010. Plant conservation: facing tough choices. Bioscience 30: 778-779.
Rivera Hernández, J.E. and Samain, M.S. 2011. Where has Aristolochia tricaudata (Aristolochiaceae) gone? New record of a critically endangered species in Oaxaca, Mexico. Revista Mexicana de Biodiversidad 82: 281-286.
Samain, M.S., Dugardin, C. and Goetghebeur, P. 2010. Peperomia reference collection: an ex situ living plant collection for scientific research. Proceedings of the 4th Global Botanic Gardens Congress, June 2010.
SBSTTA, 2010. Progress in the implementation of Global Strategy for Plant Conservation and development of a consolidated update beyond 2010. UNEP/CBD/SBSTTA/14/INF/16.
Sharrock, S., Hird, A., Kramer, A. and Oldfield, S. (Comp.) 2010. Saving plants, saving the planet: Botanic Gardens and the implementation of GSPC Target 8. BGCI, Richmond, UK.
Marie-Stéphanie Samain and Eduardo Cires
Spermatophytes & Botanical Garden
K.L. Ledeganckstraat 35