Chromosome Number Evolution in Vascular Plants

Chromosome number variation underpins much of the genomic diversity observed in vascular plants, arising principally through two processes: polyploidy, the duplication of entire chromosome sets, and dysploidy, gains or losses of individual chromosomes via fission or fusion. These karyotypic changes can accompany speciation, influence recombination rates and shape ecological adaptation. Patterns of chromosome evolution are heterogeneous among clades, reflecting lineage-specific histories of whole-genome duplication, structural rearrangements and life-history traits. In many angiosperm groups polyploidy has sparked rapid radiations, whereas dysploid shifts often persist over longer time frames and may contribute to fine-scale diversification. Advances in cytogenetics, comparative genomics and probabilistic modelling are now allowing researchers to reconstruct ancestral chromosome states, infer rates of chromosomal transitions and link karyotypic shifts to environmental and reproductive factors. The global significance of these findings extends from the elucidation of plant biodiversity hotspots to the improvement of crop breeding programmes by harnessing natural mechanisms of genome change.

Research from Nature Portfolio

A quantitative assessment of chromosome number variation across endemic vascular plants revealed that phylogenetic inertia exerts a strong influence on karyotype, whereas environmental factors such as habitat disturbance and stability modulate chromosome counts. By fitting Ornstein–Uhlenbeck models to a phylogeny of over eight hundred taxa, researchers demonstrated that open, drought-prone habitats tend to select for lower chromosome numbers, while shaded, perennial herbs in stable environments maintain higher counts. This work highlights the interplay between evolutionary history and ecological context in driving chromosome number evolution across diverse angiosperm clades.

Chromosome Number Evolution in Vascular Plants publication trend

The graph below shows the total number of articles in chromosome number evolution in vascular plants across all publications each year (not limited to Nature Index journals).

Technical terms

Polyploidy: Duplication of the entire set of chromosomes, resulting in organisms with more than two homologous sets.

Dysploidy: Incremental changes in chromosome number through the gain or loss of individual chromosomes via fusions or fissions, without whole-genome duplication.

Cladogenesis: Evolutionary divergence of a lineage into two or more distinct clades, often associated with karyotype differentiation.

Anagenesis: Gradual evolutionary change within a single lineage without branching speciation, which may include chromosome number shifts.

Ornstein–Uhlenbeck model: A statistical framework for modelling trait evolution under stabilising selection around one or more adaptive optima.

ChromoSSE: A probabilistic model that estimates rates of chromosome number transitions along phylogenetic branches, distinguishing cladogenetic from anagenetic events.

References

1. The interplay between climatic niche evolution, polyploidy and reproductive traits explains plant speciation in the Mediterranean Basin: a case study in Centaurium (Gentianaceae). Frontiers in Plant Science (2024).
2. Polyploidy Expands the Range of Centaurium (Gentianaceae). Frontiers in Plant Science (2021).
3. Karyotypic Changes through Dysploidy Persist Longer over Evolutionary Time than Polyploid Changes. PLOS ONE (2014).
4. The Evolution of Chromosome Numbers: Mechanistic Models and Experimental Approaches. Genome Biology and Evolution (2020).
5. Unscrambling phylogenetic effects and ecological determinants of chromosome number in major angiosperm clades. Scientific Reports (2018).