How Do We Begin an Off-Site Cycad Collection?

A major challenge for off-site preservation of cycads will be to ensure that sexually propagated plants do not become museum specimens incapable of surviving under natural conditions (Barrett and Kohn, 1991). Therefore, to have a successful off-site program, as well as to enhance the preservation and research value of the collections, it is important to obtain the collection in such a way as to maximize the amount of genetic diversity within each taxon.

Before initiating the development of a cycad off-site program, the objectives of the collection must be well defined and the associated institution must make long-term preservation, financial, and space commitments to the program. Too often off-site projects fail to come up to expectations because the taxonomic and biological bases of the original samples are inadequate, either from how they were obtained or the lack of complete documentation for future propagules derived from the original collection. In fact, the majority of existing public and private cycad collections do not have preservation value and cannot be considered off-site collections because of the lack of documentation on how the plants were obtained.

Prior to the development of an off-site cycad program, one should understand the factors that control the life history and breeding system for the cycad taxon being preserved and propagated. The life history and breeding system of a taxon have a tremendous impact on the short- and long-term financial commitment and the land space required for development and management of an off-site collection. Knowing these factors provides the necessary background to maximize the genetic diversity of the taxon being sampled, the number of plants required to begin the off-site collection, and how to manage, long-term, the resulting collection.

Maximizing the genetic variability within an off-site cycad collection begins when the original plants are collected in the taxon’s native habitat. The original collection obtained from the native population is called the core collection. A complete understanding and full documentation of the core collection will have a major impact on what plants become part of the off-site collection and what male and female plants should be crossed in the future to produce seeds for the next generation, other gardens, and potential other off-site collections. The following three items must be considered when developing the core collection.

1. Collectors must indicate how many plants were sampled within a population.
2. Collectors should try to represent each mother plant equally.
3. Seeds collected from different mother plants must be kept separate and accessioned accordingly.

Based on two studies produced by the author, using the technique of starch gel electrophoresis, the total genetic diversity within a cycad population can typically be represented by obtaining two seeds from five widely scattered mother plants within a population (Walters and Decker-Walters, 1991; Walters, Yang, and Decker-Walters, n.d. and citations within). Therefore, the goal for representing a population sample within an off-site collection is to have a minimum of ten plants grown to coning stage.

Of course, the above number of ten plants derived from collecting two seeds from five mother plants assumes that all ten seeds germinated, all ten seedlings grew to maturity, all ten of the resulting plants coned, at least five of the ten plants were female, and that the five females produced seed for the next generation. The odds of meeting all of these requirements are almost zero. Seeds do not germinate, seedlings often don’t survive to planting size, disease and insects can kill a plant at any stage, and, typically, the odds are much higher for having a male plant over a female plant. The author recommends that to have at least five females and five males representing the genetic diversity of a population, five seeds each from five widely scattered mother plants should be collected. Removal of five seeds from a single mother plant within a population would essentially have no impact on future generations, since one female may produce from 50 up to 200 seeds (Donaldson 1995).

In some cases, seeds from five plants are not always available within the natural habitat at a specific collecting time. When there are less than five plants with seed, one should try to obtain a total of at least 25 seeds from as many mother plants as possible or, better yet, return to the site at another time to see if other female plants have seeds.

The resulting off-site population sample should include a minimum of 15 plants going into the ground and grown to maturity. This assumes that of the 25 seeds originally collected, 15 seeds germinated and made it to planting size. Planting 15 plants should support having a total of five female plants for the production of future generations.

Cycad field investigators have reported that numerous cycad taxa do not cone in their natural habitat. Of course, it could be the timing of the field investigation, the present-day ecological environment the plant is growing within, or that the existing plants are all too young to cone. This raises the question of how to sample a population that does not appear to be producing seeds. Removal of an entire plant is the very last resort for a propagule for an off-site collection. The present size and health of the existing population, legal aspects, and the future stability of the population all need to be considered prior to removing a plant. Numerous cycad taxa produce underground suckers or bulbuls on the stem. Sampling of one sucker or bulbul from the plant is a viable option. It is important that the source plant is not damaged and that once the sucker or bulbul is removed, the wound that was created is sealed with a protective fungicide paste. The total number of suckers, bulbuls, or plants that are removed will depend on many factors such as those stated above. One bulbul or one sucker from 20 plants should be sufficient, if available.

Keeping in mind that genetic variation is the raw material that increases the chance of a target taxon surviving through unexpected circumstances in off-site cycad collections, diversity can be increased by including multiple population samples. The establishment of an off-site collection derived from multiple populations of a taxon will naturally increase the diversity of the collection since the core collection will have captured both intrapopulation diversity and interpopulation diversity. The Center for Plant Conservation (1991) recommends that for taxa with more than five known populations, the core collection should contain samples from four to five populations covering the geographic range of the taxon. If less then five populations of a taxon are known, collections should be made from all populations.

How Do We Maintain, for the Future, an Off-Site Collection?

The core collection is the best source to produce seed for future demands on the off-site collection for enhancement of the existing collection, the creation of additional public and private garden off-site collections, and plants for reintroduction to the native site. Since the core collection is the most valuable portion of an off-site collection, plants within the collection should be clearly labeled so as not to confuse them with future generations.

Since cycads are extremely long-lived perennials, maintaining the health of the original wild collection is vital. The high labor and financial demands of annual and short-lived perennial off-site collections, which require constant evaluation and replacement of the original collection, are not factors in cycad collections, however.

The future long-term health of the collection starts with first identifying a long-term site for the collection. Soils, drainage, humidity, canopy cover, and amount of rain must all be considered when choosing a site for a specific taxon. Maximizing the health and vigor of each plant during the first three years after planting will be extremely beneficial for the future. Once a cycad adjusts to a new site, and once a regular schedule for irrigation and fertilization is developed based on the soils and the site, the collection will require less and less time and financial investment as decades pass.

If the plants are healthy and natural disasters do not occur, the plants will outlive any individuals overseeing or directing the off-site collection. Therefore, the selection of an appropriate long-term growing site must also become part of an institution’s master site plan. The commitment to a healthy maintenance schedule for the original collection must also become integrated into the long-term goals for an institution.

There are two ways of propagating off-site cycad collections: vegetative propagation and sexual reproduction. Vegetative propagation has the advantage that the original genotype, the genetic make-up of the individual, is preserved. However, with vegetative propagation on a long-term scale, the expression of natural variability that is required for long-term survival may be suppressed (Esser 1976). Sexual reproduction includes the production of seeds.

Seed production should include a male and a female originally collected from different mother plants within the same population. As the original collection matures and ages, some plants may be lost and need replacement, requiring further enhancement of the existing collection or development of other off-site collections. Replacing plants or enhancing the collection should always begin with seeds from the original collection. Seeds produced for institutions for research and educational purposes and for the private sector should be sent with full documentation of the parents along with the pollination methods used to produce the seeds. Individuals will appreciate the seeds more and place a higher value on them, knowing that they came from wild-collected parents from a known locality and the pollination method used to produce them.

Seed production within an off-site collection can be accomplished in three ways:

1. The first is to maintain the collection near the native population site so that natural pollinators will produce the seed.
2. The second is to collect the pollinators along with the core collection and have seeds produced by insect pollination. The institution would then have to make a commitment to preserve the pollinator along with the off-site collection. Of course, one would have to plan that the pollinator would remain associated with the collection (not always the case) and support seed production. One must be careful if the collection contains more than one taxon; using insects as pollinators might create hybrid seed of unknown male parentage. An institution should be aware that introduction of the pollinator from another country might not be allowed because of potential ecological disturbances to the native fauna where the off-site collection is located.
3. The third is to produce seeds from hand pollination.

The first and second options have the advantage of supporting the preservation of the pollinator for possible reintroduction into the wild. The disadvantage of depending on insects for off-site collection seed production is that the parentage of seeds would be unknown, and therefore, it would be almost impossible to quantify that the genetic diversity of the core collection is being maintained.

Although the pollination biology of most cycad taxa is not known, it does appear that pollen dispersal by wind may play a factor in some taxa or at some level in addition to insect pollination. Studies on the pollination biology of the plants within an off-site collection are vital during the early years of cone production. If wind pollination does produce seed set, hand pollination followed by bagging will be required to ensure the known genealogy of the seeds that are produced.

Replication (duplication) of critical off-site collections is of vital importance. Even with the most carefully managed and planned collections, the unexpected can happen. The institution developing an off-site collection should consider collecting material for another institution. An excellent practice when collecting in another country is to collect enough material (only if the population can handle this) so the seeds can be divided in half: one half stays with an institution within the country of collection and the other half goes to the collector’s institution. If this is not possible, seed from the off-site collection should be produced and sent, along with complete documentation, to another institution. Institutions generating seeds from their collections should also consider donating seeds to individuals who have shown an interest in and commitment to maintaining an off-site collection of a taxon. This practice allows private collectors and growers to obtain thoroughly documented seeds for their collections; an option which is not typically available to most of them since they are only able to obtain legally, undocumented material.

It Is Not Cheap

It is one thing to promote that you want to save the world -- it is quite another thing to do it.

Conservation projects must be undertaken according to a management plan that is part of the ongoing master and strategic (financial) plans for a garden or research institution. A long-term commitment must be made initially before a conservation program can be initiated. When this commitment is not in place, as is the situation more often than not, the institution ends up with a few endangered plants representing various species that are fully domesticated and have essentially become museum specimens. For off-site preservation to amount to more than the maintenance of a few endangered specimens, the institution must commit space (both nursery and ground space), time (for collecting, horticultural care, and propagation), and finances (e.g., horticultural supplies, labor, collecting costs, etc.; Whitelock, 1995). Sufficient space must be made available to grow colonies of particular taxa, and knowledgeable workers with an interest in conservation must be provided to care for them on a long-term basis (Whitelock, 1995).

Botanical gardens and allied institutions need to make a major financial commitment to conservation and preservation -- for example, a percentage of their annual budget. Dividends are and will continue to be small, but they come in the future in the form of a more aware and educated public - people better able to respond to calls for conservation-oriented lifestyles and collections to encourage research on the taxa (Given, 1994).

Editor’s Note: This is the second of a series of three articles on ex situ preservation of cycads.

Literature Cited

Barrett, C. H. and J. R. Kohn 1991. Genetic and evolutionary consequences of small populations size in plants: implications for conservation. In Genetics and Conservation of Rare Plant,s eds. D. A. Falk and K. E. Holsinger. Oxford University Press, New York.

Center for Plant Conservation. 1991. Genetic sampling guidelines for conservation collections of endangered species. In Genetics and Conservation of Rare Plants, eds. D. A. Falk and K. E. Holsinger. Oxford University Press, New York.

Donaldson, J. 1995. Understanding cycad life histories: an essential basis for successful conservation. In Cycad conservation in South Africa: issues, priorities and actions, ed. J. Donaldson. The Cycad Society of South Africa, Matieland, South Africa.

Esser, K. 1976. Genetic factors to be considered in maintaining living plant collections. In Conservation of threatened plants, ed. J. B. Simmons, R. I. Beyer, P. E. Brandham, G. L. Lucas, and V. T. H. Parry, pages 185-197. Plenum Press: London.

Frankel, O. H., A. H. D. Brown, and J. J. Burdon. 1995. The conservation of plant biodiversity. Cambridge University Press, Great Britain.

Given, D. R. 1994. Principles and practice of plant conservation. Timber Press: Portland Oregon. 292 pages.

Osborne, R. 1989. Encephalartos transvenosus. Encephalartos 20: 10-18.

Vovides, A. P. 1992. Cycad conservation in Mexico: Dioon edule Lindl., a study case. In Cycad 90 Second International Conference on the Biology of Cycads (Abstracts).

Vovides, A. P. and C. Inglesias. 1994. Dioon edule: conservation and propagation in Mexico. Cycad Newsletter 18(3): 18-20 (originally labeled as Volume 17 (3)).

Walters, T. W., S. L. Yang, and D. S. Decker-Walters. n.d. The systematic implications of allozyme patterns in Chinese Cycas. (available from the author)

Walters, T. W. and D. S. Decker-Walters. 1991. Patterns of allozyme diversity in the West Indies cycad Zamia pumila (Zamiaceae). American Journal of Botany: 436-445.