UBC Theses and Dissertations

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UBC Theses and Dissertations

Metavariation and long term evolutionary patterns Blachford, Alistair M


By definition "adaptability" is the ability of living systems to cope with change. Genetic adaptability requires the production of genetic variation. The view that variation production is undirected or random, i.e. unconnected with selection, implies that selection does not tailor genetic adaptability. But many genetic elements are known to modify processes of variation production, and secondary selection can act on them, so that view is not justified. Over the longer term, natural selection 'favors' properties important, in maintaining immediate fitness, as well as properties important for persistence in the short term. Genetic adaptability is less important in the short term, and is ignored in models based on short term definitions of fitness (e.g. relative effective rate of increase). If "fitness" is to be "the properties favored by natural selection", then its definition should be time scale dependent. Currently prevalent short term definitions of the action of natural selection should not be allowed to hamper consideration of the role of slow processes in determining long term evolutionary patterns. A review of patterns in genome size, and the existing explanations for them, reveals that most explanations are based on notions of adaptedness to the state of the environment. An explanation of genome size patterns based on the rate of change of environments is proposed. It is hypothesized that part of the genome is involved in regulating variation production, and that more DNA means slower production of additive genetic variation. This new hypothesis is simple, general, and testable, but requires more evidence. The question is raised of whether genomes might be organized to facilitate the adjustment of genetic variation production by natural selection.

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