Fissions, fusions, and translocations shaped the karyotype and multiple sex chromosome constitution of the northeast-Asian wood white butterfly, Leptidea amurensis

Previous studies have shown a dynamic karyotype evolution and the presence of complex sex chromosome systems in three cryptic Leptidea species from the Western Palearctic. To further explore the chromosomal particularities of Leptidea butterflies, we examined the karyotype of an Eastern Palearctic species, Leptidea amurensis. We found a high number of chromosomes that differed between the sexes and slightly varied in females (i.e. 2n = 118-119 in females and 2n = 122 in males). The analysis of female meiotic chromosomes revealed multiple sex chromosomes with three W and six Z chromosomes. The curious sex chromosome constitution [i.e. W-1 (3)/Z(1) (6) (females) and Z(1) (6)/Z(1) (6) (males)] and the observed heterozygotes for a chromosomal fusion are together responsible for the sex-specific and intraspecific variability in chromosome numbers. However, in contrast to the Western Palearctic Leptidea species, the single chromosomal fusion and static distribution of cytogenetic markers (18S rDNA and H3 histone genes) suggest that the karyotype of L. amurensis is stable. The data obtained for four Leptidea species suggest that the multiple sex chromosome system, although different among species, is a common feature of the genus Leptidea. Furthermore, inter-and intraspecific variations in chromosome numbers and the complex meiotic pairing of these multiple sex chromosomes indicate the role of chromosomal fissions, fusions, and translocations in the karyotype evolution of Leptidea butterflies. (C) 2016 The Linnean Society of London