Inference of Ancient Polyploidy from Genomic Data.

Whole-genome sequence data have revealed that numerous eukaryotic organisms derive from distant polyploid ancestors, even when these same organisms are genetically and karyotypically diploid. Such ancient whole-genome duplications (WGDs) have been important for long-term genome evolution and are often speculatively associated with important evolutionary events such as key innovations, adaptive radiations, or survival after mass extinctions. Clearly, reliable methods for unveiling ancient WGDs are key toward furthering understanding of the long-term evolutionary significance of polyploidy. In this chapter, we describe a set of basic established comparative genomics approaches for the inference of ancient WGDs from genomic data based on empirical age distributions and collinearity analyses, explain the principles on which they are based, and illustrate a basic workflow using the software "wgd," geared toward a typical exploratory analysis of a newly obtained genome sequence.