Genome Evolution and Diversification in Palms

Genomic analysis has revealed no correlation between genome size and organismal complexity, known as the “C-value paradox”. However, recent studies demonstrate relationships between genome size and species diversity, suggesting polyploidy or other phenomena potentially confer selective advantages due to the introduction of genetic novelty. Processes contributing to such immense genome size variation include polyploidy (genome doubling), tandem duplication, expansion/contraction of repetitive regions such as transposable elements, illegitimate/intramolecular recombination, fractionation/diploidization, inefficient ‘cleanup’ mechanisms, and possibly selection for smaller genomes. One such group is the palms (Arecaceae), representing diverse, widespread, and ecologically dominant components of tropical ecosystems, with >2,500 species. Modal chromosome numbers are 16-18 but otherwise vary widely, while the pattern of genome size variation and its causal mechanisms remain unclear. Ultimately we aim to test the hypothesis that polyploidy has facilitated species diversification in palms within the context of their closest relatives, the commelinid monocots, and to investigate mechanisms of genomic change. We comparatively address relationships between chromosome number and C-value across the family and reconstruct ancestral estimates of these values. We use publically available and newly generated genomic and transcriptomic data to investigate evidence for polyploidy among the commelinids and within the palms (at the subfamily level) by comparing the age distribution of paralogous, duplicated genes. Lastly, we address causal mechanisms of genome size variation by exploring repeat type and content. Disentangling the causes of genome size variation in palms will help elucidate the genetic conditions facilitating adaptive radiation and ecological success in other economically and ecologically important clades.