LACK OF CLONAL VARIATION AMONG CANADIAN POPULATIONS OF THE CORN LEAF APHID, RHOPALOSIPHUM-MAIDIS FITCH (HOMOPTERA, APHIDIDAE)

The extent of allozyme variation and the amount of genetic divergence were assessed among populations of the aphid Rhopalosiphum maidis in O ntario. Allozyme analysis of individuals from 12 sites revealed no pol ymorphism for 32 loci. In addition, the extent of karyotypic, allozyme , and mitochondrial DNA (mtDNA) variation was examined for clones from North America, Europe, and North Africa. As previously noted, chromos ome number varied in relation to the host-plant on which aphids were c ollected, but neither allozyme nor mtDNA patterns allowed discriminati on among clones. Further work is needed to determine whether the lack of genetic diversity in R. maidis is linked with its recent introducti on to North America or with its loss of a sexual phase.