with high chromosome numbers of ancient polyploid origin? If so, what can we learn about gene silencing from these plants? How extensive has gene silencing been, and is there evidence for the cooption of duplicated genes for new function? The study of polyploidy is a dynamic and open area of research, ranging from molecular genetic comparisons to population genetics, with important implications for the biology and evolution of the majority of plant species.
We thank Kent Holsinger and an anonymous reviewer for helpful comments on the manuscript. This research was supported, in part, by the National Science Foundation. This work is dedicated to the memory of G. Ledyard Stebbins.
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