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Population Differentiation in Agrostis tenuis Sibth I. Morphologica Differentiation

A. D. Bradshaw
The New Phytologist
Vol. 58, No. 2 (Oct., 1959), pp. 208-227
Published by: Wiley on behalf of the New Phytologist Trust
Stable URL: http://www.jstor.org/stable/2429220
Page Count: 20
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Population Differentiation in Agrostis tenuis Sibth I. Morphologica Differentiation
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Abstract

In order to investigate the pattern of population differentiation in Agrostis tenuis, sixty tillers were collected from each of thirty-three areas mainly in central Wales. These were grown under garden conditions in Aberystwyth. In a subsequent experiment five of these areas were sampled again by tillers, and at the same time sampled by seed. These samples were grown under garden conditions in Bangor. Numerous differences between these population samples were recorded. The main conclusions are as follows: (i) The environment is the dominating factor in determining population differentiation. (ii) Although the distribution is continuous, distances of about 50 m or less are sufficient to effectively isolate populations from one another. (iii) Thus the species is able to evolve under the influence of natural selection in response to very local variations in environment. (iv) Since the environment is a graded patchwork of different conditions, the pattern of differentiation is similar. (v) It is, therefore, not possible to classify effectively such intraspecific variation. (vi) It is likely that this situation is to be found in most other outbreeding continuously distributed plant species occupying a wide range of habitats.

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