The macrophysiology of insect thermal biology in a changing world.

It is well-known that the earth's climate is currently in a time of fast change, which it is widely accepted is due to the effects of pollution in the atmosphere. It is also well-known that the distribution of at least some species is limited by their ability to tolerate very high or very low temperatures, such that they can only live in areas where the climate is suitable. Temperature may be especially important for ectotherms, which cannot physiologically regulate their body temperature. It follows that changes in climate might lead to changes in the distribution of species as some areas become more suitable and others less so. This means that some species may invade areas where they did not live before, which may be a problem if they are crop pests, for example. Other species may not be able to cope with the new climates and so go extinct. These potential problems mean that it is important to understand how species will respond to temperature changes. However, at the moment there are many aspects of species responses to temperature change that we don't understand. For example, we might expect species from temperate climates, which experience both high and low temperatures, to be better able to cope with change than tropical species, which only experience high temperatures, and than polar species, which only experience relatively low temperatures. Yet, we don't know whether this is actually true. We don't know whether a species that increases its tolerance of high temperatures loses its tolerance to low temperatures. We don't know how far the tolerances of species can be changed by selection for better tolerance or high or low temperatures. We don't know whether different populations of a species respond differently to temperature changes depending on whether or not they are near the limits to that species' distribution. These are the questions that this grant will address, using aphids as a model system. Aphids are useful study organisms because they are easy to grow in the laboratory, and some features of their thermal biology have already been worked out. Moreover, aphids are important crop pests that also spread crop diseases, so their response to climate change could have significant implications for agriculture.