Local Ecotype The Importance of Using Local Plant Material

Prairie restorationists generally try to reconstruct, on a given planting site, a prairie ecosystem that looks and functions as much as possible like the prairie ecosystem that originally existed on that site. In order to do this, prairie restorationists try to use plant material that reflects the original flora as exactly as possible. This ideally means that seed used for prairie conservation originated in remnants (original, never plowed prairies) near the reconstruction site. The seed many have been collected directly from these nearby remnants, or may have been propagated (from seed collected from the remnants) on another site.

Using such local seed can sometimes make prairie reconstruction more difficult or expensive. But if seeds of distant genetic origin is used, meaning seed collected or descended from prairie remnants that are many miles fro the planting site, the resulting prairie reconstruction is much less likely to be a reflection of the prairie that evolved at the planting site originally. Furthermore, the plants growing from seed adapted to a different area will probably be different than those adapted to the local area. Problems may arise from inappropriate bloom periods, reduced tolerance to environmental extremes, or pest susceptibility. Conversely, the distant-origin plants may be more aggressive than local plants of the same species, and may crowd out other species in the reconstruction.

The reason this would happen lies in the fact that while the same species of plant may occur over a wide geographical range, there actually is a gradient of genetically distinct plants (although still considered the same species) adapted to the environmental differences caused by geographical changes within the species range. This means that plants from one area are not the exactly the same, genetically, as plants of the same species from another area.

If a mix of plants from several areas are planted together the genetic adaptations that occurred along the original geographical gradients are blended together. The end result of this blending is that the plants with genes best suited for that specific environment eventually hybridize with the less well suited plants and the offspring do not have the best genetics for coping with that environment.

Some of these adaptations to environmental differences are relatively simple to measure or document; more northern species may be more cold tolerant or bloom after a shorter growing period than their more southerly counterparts, for example. Other differences are more subtle and harder to identify, but nevertheless contribute importantly to the overall fitness of a given plant to a specific environment. These adaptations, both obvious and subtle, are important to the interrelationships of the total assemblage of plants and animals in any given natural community. To the prairie conservationist they represent an important reason to meet the challenge of using plant material from specimens that originated as closely as possible to the restoration site.

This concept of locally adapted plants having a superior ability to survive a particular set of environmental conditions is well demonstrated in agricultural practice. Farm seed suppliers provide seed differentiated by maturity dates so that farms in the north have crops that set seed in a shorter amount of time than those in the south, because the growing season gradually decreases along a gradient moving north. Even within Iowa more northern farmers use crops with slightly shorter growing seasons than those used by farmers in the southern parts of the state. Further evidence for differences in blooming period are seen when a farmer forced into a late season planting chooses seed bred for more northern areas to insure the plants successfully set seed before harvest time.

For these reasons, prairie restorationists do try to obtain seeds from remnant prairies (sites that have never been plowed and therefore reflect the original adaptations to that specific area) and use that seed when planting new “reconstructed” prairies near remnants. These seeds are referred to as having a “local ecotype”, meaning they carry the genetic adaptations of the plants that were originally growing in that specific area. Within an ecotype there is still some genetic variation but the pool of plants reflects the adaptations to the specific local environment.

Less concern about local ecotype usage is directed at the home gardener wishing to use native species of plants to help improve the soil and reduce water and chemical inputs in his backyard. In this case the goal of reproducing the original prairie flora is replaced by more typical gardening concerns, and due to isolation from intact prairies the potential for gene pool contamination is greatly reduced. The IPN wishes to stress it is always preferable to use local ecotype plants, but in some cases not imperative.