Although numerous studies have surveyed the frequency with which different plant characters are associated with polyploidy, few statistical tools are available to identify the factors that potentially facilitate polyploidy. We describe a new probabilistic model, BiChroM, designed to associate the frequency of polyploidy and chromosomal change with a binary phenotypic character in a phylogeny. BiChroM provides a robust statistical framework for testing differences in rates of polyploidy associated with phenotypic characters along a phylogeny while simultaneously allowing for evolutionary transitions between character states. We used BiChroM to test whether polyploidy is more frequent in woody or herbaceous plants, based on tree with 4,711 eudicot species. Although polyploidy occurs in woody species, rates of chromosome doubling were over six times higher in herbaceous species. Rates of single chromosome increases or decreases were also far higher in herbaceous than woody species. Simulation experiments indicate that BiChroM performs well with little to no bias and relatively little variance at a wide range of tree depths when trees have at least 500 taxa. Thus, BiChroM provides a first step towards a rigorous statistical framework for assessing the traits that facilitate polyploidy.

BiChroM Raw R Files1. Dataset and tree 2. Raw R files for optimizations 3. Full model optimizations 4. Reduced model optimizations 5. Profile rhoH and Profile rhoW 6. Bivariate profile rhoqH and Bivariate profile rhoqW 7. Raw R files for simulations 8. Simulations number of taxa 9. Simulations for tree heightBiChroMRawRfiles.zip