"For thermodynamic reasons, cold temperatures present a challenging problem for ectothermic [cold-blooded] organisms because they slow biological processes, thus reducing rates of movement, feeding, and population growth," explains author M. R. Frazier.

Many researchers believe that biochemical adaptations can eventually compensate for the effects of low body temperatures, but Frazier and his colleague's recent thermodynamic model, forthcoming in the October issue of The American Naturalist, argues against such compensation.

To address this controversy, the researchers conducted a comparative analysis of published data on the thermal dependence of population growth rate for 65 insect species. They found that insects adapted to cold environments have slower maximum population growth rates than those adapted to warm environments, despite their long evolutionary history in such environments.

"At least with respect to insect population growth rates," says Frazier, "our data suggest that hotter is better. We see little evidence of evolutionary compensation."

This research suggests that adaptation to warmer or to colder temperature inevitably alters the population dynamics of insects, a result that has important consequences for agriculture, public health, and conservation.

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