@ARTICLE{TreeBASE2Ref20156, author = {Kyong-Sook Chung and Andrew L. Hipp and Eric H Roalson}, title = {Chromosome Number Evolves Independently of Genome Size in a Clade with Non-Localized Centromeres (Carex: Cyperaceae).}, year = {2012}, keywords = {Agmatoploidy, karyotype, holocentric chromosomes, phylogenetic comparative methods}, doi = {}, url = {http://}, pmid = {}, journal = {Evolution}, volume = {}, number = {}, pages = {}, abstract = {The effects of chromosome rearrangement on genome size are poorly understood. While chromosome duplications and deletions have predictable effects on genome size, chromosome fusion, fission, and translocation do not. In this study, we investigate genome size and chromosome number evolution in 87 species of Carex, one of the most species-rich genera of flowering plants and one that has undergone an exceptionally high rate of chromosome rearrangement. Using phylogenetic generalized least squares regression, we find that the correlation between chromosome number and genome size in the genus grades from flat or weakly positive at fine phylogenetic scales to weakly negative at deeper phylogenetic scales. The rate of chromosome evolution exhibits a significant increase near the crown of a species-rich clade that arose approximately 5 million years ago. Genome size, however, demonstrates a nearly constant rate across the entire tree. This decoupling of the evolution of genome size from chromosome evolution may explain the high lability of chromosome number in the genus, as chromosome number shifts do not incur any selective disadvantages in terms of genome size. Our results also suggest that transitions in the rate of chromosome number evolution may govern lineage diversification in the temperate zone?s most species-rich angiosperm genus.} }

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