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The Comparative Biology of Closely Related Species Living in the same Area: IX. Rumex: The Nature of Adaptation to a Sea-Shore Habitat

P. B. Cavers and J. L. Harper
Journal of Ecology
Vol. 55, No. 1 (Mar., 1967), pp. 73-82
DOI: 10.2307/2257717
Stable URL: http://www.jstor.org/stable/2257717
Page Count: 10
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The Comparative Biology of Closely Related Species Living in the same Area: IX. Rumex: The Nature of Adaptation to a Sea-Shore Habitat
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Abstract

The reactions of Rumex obtusifolius and both the inland and maritime forms of R. crispus were compared under laboratory simulated maritime conditions. The maritime taxon contrasted with the inland taxa in the following respects. (i) Seed of the maritime form of R. crispus: (a) floated in sea water, (b) was slightly more inhibited in germination by dilute sea water, and (c) germinated more rapidly than the inland form in fresh water after soaking in sea water. (ii) Seedlings of the maritime form of R. crispus: (a) rooted more successfully under a seaweed mulch, (b) produced longer tap roots, (c) suffered less from sea water dousing, and (d) were at an advantage in mixtures with the inland form when growing on shingle substrates, a situation reversed on a garden soil. (iii) Inflorescences of the maritime form of R. crispus suffered less from gale damage than the inland forms. (iv) Plants of the inland form of R. crispus often flowered in the first year. This was never observed for the maritime forms of R. crispus. The differences between inland and maritime taxa were never absolute and it is concluded that the maritime form occupies its rather exclusive habitat by virtue of adaptations affecting stages throughout its life cycle.

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