On the neo-sex chromosomes of lepidoptera

Abstract

Chromosome rearrangements can play an important role in adaptive evolution and speciation with gene flow. Here, we briefly review state of the art in chromosomal speciation, along with the classic model of sex chromosome evolution. The main focus lies on sex chromosome-autosome fusions, i.e., neo-sex chromosomes. We describe the presence of neo-sex chromosomes in moth and butterflies (Lepidoptera), the largest group with female heterogamety. Despite the relative stability of lepidopteran karyotypes, fusions which result either in multiple sex chromosomes (W1W2Z or WZ1Z2) or large sex chromosome pairs occurred at a surprisingly high frequency throughout their evolution. We discuss the role of meiotic drive, genetic drift, and selection in the establishing of these derived sex chromosome systems. It is hypothesized that the association between sex-linked reproductive isolation or female preference and larval performance may contribute to ecological specialization and species formation in Lepidoptera.