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The Integration of Neighbourhood Effects by Clonal Genets in Solidago Canadensis

D. C. Hartnett and F. A. Bazzaz
Journal of Ecology
Vol. 73, No. 2 (Jul., 1985), pp. 415-427
DOI: 10.2307/2260484
Stable URL: http://www.jstor.org/stable/2260484
Page Count: 13
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The Integration of Neighbourhood Effects by Clonal Genets in Solidago Canadensis
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Abstract

(1) When clones of Solidago canadensis were grown experimentally with pure stands of different species, the neighbouring species had different effects on ramet shoot-growth, flower-head production, and clonal growth. In general, S. canadensis shoot growth and flower production were greatest in the neighbourhood of Poa pratense, and lowest among Aster pilosus, whereas clonal growth was greatest among ramets growing in the A. pilosus neighbourhood and lowest in the Solidago canadensis neighbourhood. (2) When clones of S. canadensis were grown experimentally with each interconnected ramet among a different neighbour species, the effects of the different neighbours were evened out. All ramets responded more or less equitably in their shoot growth, reproduction, and clonal growth, regardless of the identity of their neighbours. These results suggest that clones integrate local neighbourhood variation and that the response of a given ramet to interference from a neighbour species is partly dependent upon the experiences of its interconnected sibling ramets. (3) There are several costs and benefits associated with maintaining physiological interdependency among ramets. Interdependent ramets may support the growth of ramets experiencing intense interference or resource limitation and may benefit from the ability to regulate internally the position and density of shoots within the clone and to overcome local variation in their environment. However, the maintenance of a network of long interconnecting rhizomes may be energetically expensive and may allow certain agents of mortality such as pathogens to spread rapidly among ramets. (4) The growth form of a clone may also influence the relationships between clonal plants and neighbours. Within-clonal Solidago canadensis ramets form pure stands, 1-several metres in diameter, that prevent the invasion of neighbours, distribute the effects of surrounding neighbour species, are buffered against neighbour interference, and expand uniformly in several directions regardless of the identity of neighbours. This is in contrast to patterns in other clonal species, e.g. Trifolium repens and Ranunculus repens in which very long rhizomes or stolons are produced and ramet interconnections are rapidly lost. These species are characterized by extensive lateral mobility and sampling of the environment, the avoidance of interference, and the differential growth of different independent portions of the genet in different parts of the habitat mosaic.

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