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Considering Genetic Diversity
in Grassland Restoration
1
Steve Smith2
Biodiversity is a multifaceted characteristic of a biological system that may involve the variety of
organisms present, the genetic differences among them, and the communities and ecosystems in
which they occur. Arranged in a hierarchical fashion, one could consider the patterns and
connections between landscapes and regions. The next level of the hierarchy would examine the
characteristics of communities and ecosystems such as abundance, frequency and richness, and at
the species level, the abundance or frequency of individual species. Genetic diversity would be
found at the base of this hierarchial scheme, and although may be the least appreciated of the
levels, is the most important. Genetic diversity is the source of variation among and within
populations, and is the ultimate source of biodiversity at higher levels.
Examination of model populations of grass species in minimally disturbed sites yields
information on community organization and genetic variation for use in restoration. A few sites in
southern Arizona have not been exposed to disturbance and serve as good sources of information.
For collection of native seed, three rules should be followed to enhance genetic diversity.
Restorationists must remember local adaptation to changes in environment may occur over a very
short distance, so collections from model populations at or near the restoration site are
recommended. The second rule relates to the size of the sample. The probability of sampling the
full range of genetic variation present in a population is directly related to the size of the sample, so
at least one hundred individuals in the model population should be sampled. Random sampling,
rule three, stresses the importance of elimination of bias in the sampling procedure.
Genetic diversity among and within the population is the ultimate source of all biodiversity.
Successful grassland restoration depends on selection of reasonable model communities and
populations. Samples from model populations for use in restoration should be large, and should be
collected randomly. To obtain a truly random sample is complicated, and very little is known about
the genetic characteristics of some plants. Collecting an overly large sample may provide an
allowance for error.
1
2
Summarized by Linda Elliott, Arizona State University, Tempe AZ.
Department of Plant Sciences, University of Arizona, Tucson AZ.
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