Geographical variation in thermal requirements for insect development

Abstract

Thermal constants, Lower development threshold (LDT) and sum of effective temperatures (SET) were recalculated from literature data for 335 insect species. Included were only populations whose development rate was ascertained in at least 4 constant temperatures of <=28°C. Variation of thermal constants was investigated in relation to geographic origin of the populations to test the prediction that LDT will decrease and SET increase with increasing geographical latitude (Trudgill, 1995). In tropics (at <= 23°N or S), LDT was high with little geographic variation. In subtropical and temperate zones there was a significant trend for decreasing average LDT with increasing geographical latitude. SET increased with geographic latitude but the scatter of data was greater than in LDT. The geographic trends of variation in thermal constants conformed to the prediction but the scatter of data was large probably due to both ecophysiological differences between the species, and errors in estimating thermal constants of development.