Data from: Chromosome number evolves independently of genome size in a clade with non-localized centromeres (Carex: Cyperaceae)

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 evolution, however, demonstrates a nearly constant rate
across the entire tree. We hypothesize that this decoupling of genome size
from chromosome number helps explain the high lability of chromosome
number in the genus, as it reduces indirect selection on chromosome
number.