Macroevolutionary insights into sedges (Carex: Cyperaceae): The effects of rapid chromosome number evolution on lineage diversification

• DOI: 10.1111/jse.12730
• Publication Date: 2021-02-01T03:33:59Z
• Authors: José I. Márquez‐C...; Santiago Martín‐B...; Pedro Jiménez‐Mejías; Andrew L. Hipp; Daniel Spalink; Robert F. C. Naczi; Eric H. Roalson; Modesto Luceño; Marcial Escudero
• Keywords: Phylogenetic Comparative Methods; 0301 basic medicine; 03 medical and health sciences; Slouch; Bioclimatic variables; Morphological characters; Diversification; Bayou; Ornstein–Uhlenbeck model; Brownian motion; 15. Life on land; QuaSSE

AbstractChanges in holocentric chromosome number due to fission and fusion have direct and immediate effects on genome structure and recombination rates. These, in turn, may influence ecology and evolutionary trajectories profoundly. Sedges of the genusCarex(Cyperaceae) comprise ca. 2000 species with holocentric chromosomes. The genus exhibits a phenomenal range in the chromosome number (2n = 10 − 132) with almost not polyploidy. In this study, we integrated the most comprehensive cytogenetic and phylogenetic data for sedges with associated climatic and morphological data to investigate the hypothesis that high recombination rates are selected when evolutionary innovation is required, using chromosome number evolution as a proxy for recombination rate. We evaluated Ornstein–Uhlenbeck models to infer shifts in chromosome number equilibrium and selective regime. We also tested the relationship between chromosome number and diversification rates. Our analyses demonstrate significant correlations between morphology and climatic niche and chromosome number inCarex. Nevertheless, the amount of chromosomal variation that we are able to explain is very small. We recognized a large number of shifts in mean chromosome number, but a significantly lower number in climatic niche and morphology. We also detected a peak in diversification rates near intermediate recombination rates. In combination, these analyses point toward the importance of chromosome evolution to the evolutionary history ofCarex. Our work suggests that the effect of chromosome evolution on recombination rates, not just on reproductive isolation, may be central to the evolutionary history of sedges.