The Ecology of Clonal Growth in Plants: Studies on Solidago Canadensis L
Hartnett, David Charles
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https://hdl.handle.net/2142/71276
Description
Title
The Ecology of Clonal Growth in Plants: Studies on Solidago Canadensis L
Author(s)
Hartnett, David Charles
Issue Date
1983
Department of Study
Plant Biology
Discipline
Botany
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Abstract
Clones of Solidago canadensis L. were studied to determine (1) the degree of physiological interdependence among interconnected ramets, (2) the ecological consequences of ramet interdependence, (3) the genet and ramet population responses to increasing plant density, and (4) the dynamics of ramets and genets in a natural colonizing population.
Ramets severed from their parental clone in the field showed reduced growth, survivorship, and reproduction relative to intact controls. In addition, patterns to photosynthesis, growth, survivorship, and reproduction of sunlit versus shaded ramets of transplanted clones indicated that shaded ramets are supported by assimilates translocated from other ramets within the clone. Therefore, ramets are not independent but are physiologically integrated such that ecologically, the genet defines the functional individual.
Both ramet interrelationships and clonal growth form may influence clonal competition. When Solidago canadensis clones were grown in pure stands of each of three different species, the three species had different effects on shoot growth, reproduction, and clonal expansion. When different interconnected ramets were grown with different species, all ramets responded equitably regardless of neighbor species. Hence one consequence of ramet interdependence is that genets can integrate local environmental heterogeneity.
In experimental populations, increasing shoot density resulted in reductions in shoot and rhizome growth, and a reduction and delay in reproduction. Shoot population densities were regulated by a combination of density dependent genet mortality, ramet mortality, and density dependent clonal growth. At high densities, genet mortality and clonal expansion of survivors resulted in a population composed of progressively fewer but larger genets with time. Interconnected ramets did not conform to weight/density relationships predicted by the "law of constant final yield". This is additional evidence that intra-clonal ramets do not function as ecologically independent individuals.
The natural Solidago canadensis population studied colonized via a single episode of recruitment 3 to 4 years after field abandonment with no subsequent genet recruitment. Genet survivorship and clonal growth were inversely related to arrival time. Among the established clones, the maintenance of a large territory, ramet interdependence, and the ability to integrate environmental heterogeneity may buffer genets against localized selective influences resulting in little differential mortality among genotypes. This may be one mechanism maintaining variation in clonal S. canadensis populations.
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