Increased chromosomal mutation rate after hybridization between two subspecies of grasshoppers.

Hybridization between two chromosomally distinct subspecies of the grasshopper Caledia captiva results in a high incidence of novel chromosomal rearrangements among the backcross progeny. Rearrangements are restricted to those chromosomes derived from the F1 hybrid parent. Chromosomal involvement is nonrandom with the same rearrangement occurring repeatedly in different backcrosses. A single individual can also generate an array of different rearrangements among its offspring. Several of the rearrangements have also been found in natural populations. The nonrandom and recurrent nature of these chromosomal mutations at high frequencies provides a plausible explanation for the establishment and fixation of chromosomal rearrangements in natural populations.