Inbreeding depression and mating system evolution in the autotetraploid Chamerion angustifolium

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Ozimec, Barbara C.

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University of Guelph

Abstract

In this thesis I investigated the role of inbreeding depression in the evolution of polyploid mating systems using the autotetraploid plant ' Chamerion angustifolium.' First, I compared the mating systems of diploid and tetraploid populations of 'C. angustifolium' and found, contrary to theoretical predictions, that both cytotypes were predominately outcrossing. Second, I quantified inbreeding depression in diploids, tetraploids and newly synthesized tetraploids, and assessed the effect of repeated selfing on the evolution of inbreeding depression in the tetraploid lineages. The magnitude of inbreeding depression was higher in diploids than tetraploids and was lowest in newly synthesized tetraploids. Inbreeding depression increased with inbreeding history. Taken together the data show that although selling among early generation polyploids may initially be selected, continued selling leads to increases in inbreeding depression that may prevent the evolution of self-fertilization. These results are counter to what is expected in diploid systems.

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autotetraploid, chamerion angustifolium, inbreeding depression, mating system evolution, outcrossing, selfing

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