Linkage studies in Tribolium castaneum (Herbst). XII. A revision of linkage group II

Abstract

Data are presented to show the linkage relationships of a number of genes in linkage group II of Tribolium castaneum and a revised map of this linkage group is presented bearing eight well-established points. Some of these points were establishable with the aid of an accidental inversion induced by gamma irradiation. Five additional mutants are also in this linkage group as a result of the revision, but their relative position needs to be established through additional linkage studies. The linkage map suggests the presence of two gene clusters, one affecting the eye color and morphology and the other including homeotic mutants that affect the morphology of the maxillary and labial palps, the thorax, and the abdominal sternites. Data are presented to show that the frequency of recombination for a number of segments in linkage group II is not equal in the two sexes. The literature bearing on the evolution of the karyotype in Tribolium is reviewed, and it is concluded, on the basis of the present evidence, that it is linkage group II and not linkage group IX that became translocated to the X and Y chromosome in a T. castaneum like ancestor to produce the much larger neo-X and neo-Y chromosomes of T. confusum. Key words: Tribolium, linkage, gamma irradiation.