The chiasmatic systems in populations of two spiny leaf beetles (Coleoptera,Chrysomelidae)

The number and distribution of chiasmata per cell at diakinesis has been analyzed in four populations ofDicladispa testacea (L.) and in two ofPolyconia caroli Lepr. both having 2n=16 and a 7+Xy_p male melotic formula. Most bivalents were unichiasmate and the distal chiasma position was the one most frequently encountered. One population ofDicladispa testacea could be distinguished from the remaining ones by the total number of chiasmata per cell. This intraspecific difference is discussed in relation with the degree of isolation between the four populations and other geographical characteristics.