Evolution of multiple sex-chromosomes associated with dynamic genome reshuffling in Leptidea wood-white butterflies

Sex chromosome systems tend to be highly conserved and knowledge about their evolution typically comes from macroevolutionary inferences. Rapidly evolving complex sex chromosome systems represent a rare opportunity to study the mechanisms of sex chromosome evolution at unprecedented resolution. Three cryptic species of wood white butterflies – Leptidea juvernica, L. sinapis, and L. reali – have each a unique set of multiple sex chromosomes with 3–4 W and 3–4 Z chromosomes. Using a transcriptome-based microarray for comparative genomic hybridization (array-CGH) and a library of bacterial artificial chromosome (BAC) clones, both developed in L. juvernica, we identified Z-linked Leptidea orthologs of Bombyx mori genes and mapped them by fluorescence in situ hybridization (FISH) with BAC probes on multiple Z chromosomes. In all three species, we determined synteny blocks of autosomal origin and reconstructed the evolution of multiple sex chromosomes. In addition, we identified W-homologs of...