Drivers of diversification in Linum (Linaceae) by means of chromosome evolution: correlations with biogeography, breeding system and habit.

This article focuses on the role of chromosome evolution in the diversification, reproductive traits, and biogeography of the genus Linum (flax species). Using phylogenetic models, the study estimated an ancestral chromosome number of n = 9 for Linum and identified multiple chromosomal changes—including polyploidy and dysploidy—occurring mainly at the tips of the phylogeny, with up to five speciation events linked to chromosomal transitions. Chromosome evolution was not correlated with heterostyly (a floral polymorphism related to outcrossing) but showed significant associations with species habit (annual vs. perennial) and geographical distribution, with polyploidy more frequent in original Palearctic areas and dysploidy rates higher in colonized regions. The findings suggest that chromosome evolution influences speciation and biogeographical patterns in Linum, although its direct impact on diversification rates appears limited.