A South American origin of the genus Dynastes (Coleoptera: Scarabaeidae: Dynastinae) demonstrated by chromosomal analyses.

The karyotypes of 5 species of Dynastes, D. hercules, D. tityus, D. granti, D. satanas, and D. neptunus, and 2 subspecies of D. hercules are compared with those of 6 other selected Dynastinae species. In the 3 former species, there are 18 chromosomes, including neo-sex chromosomes formed by the fusion of an acrocentric autosome with the X and Y chromosomes. In all other species, including D. neptunus and D. satanas, free X and Y chromosomes are observed in 20,Xyp karyotypes. The acrocentric autosome presumably involved in the fusion is present in D. neptunus and D. satanas (pair No. 8). It replaces a submetacentric observed in the other Dynastinae species. Thus, the karyotypes of D. neptunus and D. satanas derive from that of ancestral Dynastinae by an inversion in chromosome 8, and those of D. hercules, D. granti and D. tityus derive from that of D. neptunus by the translocation of this inverted chromosome to sex chromosomes. Because the Dynastes species with the most derived karyotype occur in North and Central America and Lesser Antilles, while D. neptunus and D. satanas are limited to the northern part of the South American Andes, we suggest a South American origin of the genus Dynastes.