Effect of latitude and acclimation on the lethal temperatures of the peach-potato aphid Myzus persicae

1 Aphids, similar to all insects, are ectothermic and, consequently, are greatly affected by environmental conditions. The peach potato aphid Myzus persicae (Sulzer) has a global distribution, although it is not known whether populations display regional adaptations to distinct climatic zones along its distribution and vary in their ability to withstand and acclimate to temperature extremes. In the present study, lethal temperatures were measured in nine anholocyclic clones of M. persicae collected along a latitudinal cline of its European distribution from Sweden to Spain. The effects of collection origin and intra- and intergenerational acclimation on cold and heat tolerance, as determined by upper and lower lethal temperatures (ULT50 and LLT50, respectively), were investigated. 2 Lethal temperatures of M. persicae were shown to be plastic and could be altered after acclimation over just one generation. Lower lethal temperatures were significantly depressed in eight of nine clones after acclimation for one generation at 10 degrees C (range: -13.3 to -16.2 degrees C) and raised after acclimation at 25 degrees C (range: -10.7 to -11.6 degrees C) compared with constant 20 degrees C (range: -11.9 to -12.9 degrees C). Upper lethal temperatures were less plastic, although significantly increased after one generation at 25 degrees C (range: 41.842.4 degrees C) and in five of nine clones after acclimation at 10 degrees C. There was no evidence of intergenerational acclimation over three generations. 3 Thermal tolerance ranges were expanded after acclimation at 10 and 25 degrees C compared with constant 20 degrees C, resulting in aphids reared at 10 degrees C surviving over a temperature range that was approximately 26 degrees C greater than those reared at 25 degrees C. 4 There was no clear relationship between lethal temperatures and latitude. Large scale mixing of clones may occur across Europe, thus limiting local adaption in thermal tolerance. Clonal type, as identified by microsatellite analysis, did show a relationship with thermal tolerance, notably with Type O clones being the most thermal tolerant. Clonal types may respond independently to climate change, affecting the relative proportions of clones within populations, with consequent implications for biodiversity and agriculture.