Local Ecotype

A local ecotype is a subset of a species that has adapted to a specific geographic environment and as a result has evolved to be genetically distinct from other members of the same species found in different environments. Different ecotypes of the same species can usually form fertile hybrids but in some cases they do not.

 

Within the conservation community there is general agreement that it is desirable to use plant material genetically similar as possible to the plant community which originally existed on the reconstruction site. However, there is some disagreement over the terminology that best describes the appropriate plant material. The IPN has chosen to use the term local ecotype to identify a collection of plants originating in a specific area and therefore carrying genetic adaptations to that specific environment. Plant material appropriate for use in prairie reconstruction projects is therefore referred to as local ecotype plants or local ecotype seed.

 

The term ecotype is often used in biological literature, usually to describe populations that have evolved in an extreme environment such as soil with unusual mineral concentrations or atypical geographical areas. By using the word local in conjunction with ecotype we identify a similar situation, a collection of plants that evolved in response to the specific local environment of an area, although the differences in environment are usually subtle rather than extreme and usually represent a geographical gradient.

 

In some instances the definition of ecotype has been restricted to populations that can no longer interbreed but in other cases the definition specifies populations that do retain hybridization potential with each other. It is the latter that the IPN includes in it’s definition.

The term ecotype implies adaptation or differentiation and therefore is more desirable than the term genotype, which is the collection of all the alleles (mutations in specific genes) in a population, including many random mutations that have not been selected for by environmental pressures.

 

Some ecological restoration literature uses the term "local origin seed" (or a similar phrase) to convey this concept. The IPN has found a tendency for people to misunderstand such phrases because they contain familiar words, so the reader may not realize an important new concept is being conveyed. The use of an uncommon term like ecotype is more likely to cause the reader to pause and realize that learning is needed.

 

A further problem encountered when using a phrase such as "local origin seed" is the tendency for readers to confuse it with "buy local", a term frequently used by commerce groups meaning "shop close to home". In this case, shopping close to home could be interpreted as a recommendation to go to the nearest retail nursery outlet, where local ecotype seeds and plants are not necessarily sold.

 

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Why is Local Ecotype important?

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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 may have been collected directly from these nearby remnants, or may have been propagated (from seed collected from the remnants) on another site.

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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 from 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.

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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.

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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.

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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.

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Guidelines for Selecting Local Ecotype Plant Material

• Find out what’s already growing on your site first

• Visit nearby remnants and nearby good reconstructions if possible to see what they are like

• Find out what species are native to your area, talk with local prairie people

• Decide on goals and needs

• If you buy seed, you need to discuss needs and goals with seed dealers and specify the seed sources you want

• Flexibility as needed (some planting sites further from remnants than other, for larger plantings, may draw from a wider area, use “Tallgrass Restoration” thoughts

• Ethics of seed collecting (basics like not over-collecting, getting permission, etc.

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