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Variation in Phenotypic Response to Light Availability between Diploid and Tetraploid Populations of the Perennial Grass Arrhenatherum Elatius from Open and Woodland Sites

Christophe Petit and John D. Thompson
Journal of Ecology
Vol. 85, No. 5 (Oct., 1997), pp. 657-667
DOI: 10.2307/2960536
Stable URL: http://www.jstor.org/stable/2960536
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Variation in Phenotypic Response to Light Availability between Diploid and Tetraploid Populations of the Perennial Grass Arrhenatherum Elatius from Open and Woodland Sites
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Abstract

1 Phenotypic plasticity and genetic differentiation may influence how natural populations colonize variable environments, and thus help explain differences in distribution of closely related taxa. The response to shading in woodland and open habitat populations of endemic diploid and widespread tetraploid Arrhenatherum elatius was studied. 2 Two questions were examined. (i) Does the widespread tetraploid A. elatius ssp. elatius show greater phenotypic homeostasis in fitness-related traits than the related Mediterranean endemic diploid ssp. sardoum? (ii) Do the two ploidy levels differ in patterns of population differentiation related to the original habitat? 3 For each ploidy level, 10 genotypes from each of three populations from woodland and three from open habitats were grown in a garden environment at two light intensity levels. 4 No differences in phenotypic plasticity of morphological, phenological and fitness-related traits studied were observed between the ploidy levels. Tetraploids showed greater vegetative and inflorescence size. 5 Tetraploid populations showed evidence of differentiation in relation to original habitat conditions: plants from open habitats had higher seed production, were taller and flowered earlier than populations from woodland habitats in both garden environments, but phenotypic plasticity did not differ between the two habitat types. No variation in phenotypic plasticity or population differentiation was observed among diploid populations from either habitat. 6 The lack of differences in plasticity between diploids and tetraploids, and the greater differentiation between woodland and open populations in tetraploids, are discussed in relation to the geographical distribution of the two ploidy levels.

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