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Genetic Diversity and Its Conservation in Natural Populations of Plants

Alan Gray
Biodiversity Letters
Vol. 3, No. 3 (May, 1996), pp. 71-80
Published by: Wiley
DOI: 10.2307/2999720
Stable URL: http://www.jstor.org/stable/2999720
Page Count: 10
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Genetic Diversity and Its Conservation in Natural Populations of Plants
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Abstract

This paper reviews patterns of genetic diversity in natural populations of plants: patterns which have emerged from more than 70 years of genecological investigation and 30 years of allozyme analysis. The compelling conclusion to be drawn from these empirical studies is that genetic diversity in most plant species lies along the axis of environmental, and specifically habitat, variability. This predominance of genotype-environment correlations, a testimony to the power and ubiquity of natural selection, demands that strategies for the conservation of genetic diversity involve sampling or protection schemes which are stratified across environments or habitat-types. The genetic response of species' populations to their environment is affected, or constrained, by a range of intrinsic biological properties such as the breeding system and external processes such as those which cause fluctuations in population size. Insight into the impact of such forces on the genetic diversity and structure of natural populations has been the major gain from studies of allozyme variation. However, there is some doubt about the neutrality of allozyme loci, and often no correlation can be found between levels of allozyme variation and those in quantitative trait loci. Furthermore, variation in intrinsic properties and external forces accounts for relatively small amounts of the between-species variation in genetic diversity (but rather more of the variation in their population genetic structure). Coupled with the remarkable, and largely unpredictable, range of diversity patterns found in rare and endangered species, this has led to the view that there are no useful generalizations on which to base conservation strategies. Each and every species must be investigated. Here I suggest that this view has been based on an inappropriate group of species (the rare and endangered) and that a habitat-based conservation strategy has generic utility. Because of the remarkably small numbers of plants needed to capture most of a species' genetic diversity, sampling, or conserving, across habitats Can be adjusted to account for the expected levels of between-population differentiation. Prediction of these levels may be improved by taking a phylogenetic approach.

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