Chromosome Evolution of Bees and Wasps (Hymenoptera, Apocrita) on the Basis of C-banding Pattern Analyses

The C-banding patterns of 71 species of bees and wasps were studied by chromosomal alteration network analysis and by karyograph analysis. Pseudoacrocentric chromosomes (A^M) with extremely elongated heterochromatic arms, which were induced by saltatory growth of constitutive heterochromatin after centric fission, were frequently observed in bees and wasps. It was suggested that the karyotype evolution of hymenopterans would have started from a low chromosome number such as 2n=2-8, and have proceeded toward increasing chromosome number (by centric fission) and arm number (by pericentric inversion) with a temporary reduction of chromsome number (by centric fusion). The evolutionary rates of these rearrangements are not constant but fluctuate.