The B chromosome polymorphism of the grasshopper Eyprepocnemis plorans in North Africa. IV. Transmission of rare B chromosome variants

In addition to the principal B chromosome (B-1) in Moroccan populations of the grasshopper Eyprepocnemis plorans, nine B chromosome variants appeared at low frequency. The transmission of five of these rare B chromosome variants through females was analysed in three natural populations. Sixteen controlled crosses provided useful information on the transmission of B-M2, B-M6 and B-M7 in Smir, B-M3 and B-M6 in SO. DE. A. (Societe de Developpement Agricole lands near Ksar-el-Kebir city), and B-M2 and BM10 in Mechra, all located in Morocco. Since six female parents carried two different B variants, a total of 22 progeny analyses could be studied. Intraindividual variation in B transmission rate (k(B)) was observed among the successive egg pods in 26.7% of the females, but this variation did not show a consistent temporal pattern. Only the B-M2 and B-M6 variants in Smir showed net drive, although variation was high among crosses, especially for B-M2. These two variants are thus good candidates for future regenerations ( the replacement of a neutralized B, B-1 in this case, by a new driving variant, B-M2 or B-M6) in Smir, the northern population where the B polymorphism is presumably older. The analysis of all crosses performed in the three populations, including those reported previously for the analysis of B-1 transmission, showed that the largest variance in k(B) among crosses stands at the individual level, and not at population or type of B levels. The implications of these findings for the occurrence of possible regeneration processes in Moroccan populations are discussed. Copyright (C) 2004 S. Karger AG, Basel.