The Crocus panrepeatome reveals the links between whole-genome duplications, repeat bursts, and descending dysploidy

Dysploidy is a crucial driver for species diversification by changing karyotypes through diploidization after a whole-genome duplication (WGD). A WGD could trigger repeat bursts but our knowledge about the evolutionary links between WGD, repeat bursts, and descending dysploidy is limited. Using Crocus as a model, we performed a panrepeatomic analysis to gain insights into the influence of WGD on repeat bursts and of repeat dynamics in descending dysploidy. We first established a phylogenetic backbone of the genus using chloroplast (cp) and 35S rDNA sequences to which we could anchor our panrepeatome data. We identified a WGD event before the initial divergence of Crocus , and nested WGD events before the divergence of some series coinciding with repeat bursts. We demonstrate repeat-linked chromosome fusions of C. longiflorus chromosomes in its dysploid relative C. vernus . This work demonstrates the links between WGD, repeat bursts, and descending dysploidy.