Recent changes in the distribution of carboxylesterase genes and associated chromosomal rearrangements in G reek populations of the tobacco aphid M yzus persicae nicotianae

We present data on the frequency of amplified E4 and FE4 carboxylesterase genes in M yzus persicae s.l. clones collected during the years 2002–2007 and 2012 in G reece. Most clones were of the tobacco aphid, M yzus persicae nicotianae. Samples from 2012 were genotyped with microsatellite DNA markers and a number of them were karyotyped. Aphid clones with amplified FE4 genes predominated in all years, whereas E4 was present in only 3.5% of all samples and always occurred in clones with FE4 . Most of the clones examined showed high carboxylesterase activity levels ( R2 resistant category). The results showed marked changes in the frequencies of the two carboxylesterase genes in the tobacco aphid populations compared to published data that were collected in G reece in the mid 1990s, when E4 was recorded on its own in 20% of all samples and in 32% of samples from tobacco. A parallel change in karyotype was also observed because the A1 ,3 translocation, which had a worldwide association with amplified E4 genes in the 1990s, was not detected in the clones analyzed in 2012. Possible causes for these changes are discussed, although selection as a result of pest management practices appears to be the major one. Novel chromosomal rearrangements were also found in M . persicae nicotianae clones. These rearrangements could be a result of clastogenic effects of nicotine, which could persist because of the holocentric nature of aphid chromosomes. The results are discussed in relation to rapid evolution events that have taken place in the tobacco aphid in G reece during the last two decades. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society , 2014, 113 , 455–470.