Abstract
AbstractThree populations of the pea aphid, Acyrthosiphon pisum (Harris), from locations between 27 and 36°S in eastern Australia were studied at five constant temperatures from 10 to 28 °C. A three-parameter, nonlinear equation accurately described developmental rate as a function of temperature for each of the five lines from each population. Maximum adult weight was attained at 20 °C. Wingless aphids developed faster and were heavier than winged aphids. There were no significant differences in developmental times among populations, and adult weights among populations differed only at 25 °C. These weight differences and other nonsignificant differences among populations showed no trends with the long-term average temperatures at the collection sites. This finding indicates that developmental rate and adult weight have not been adapted to temperature in the 5 years since the aphids were introduced. The maximum rate of development, optimum temperature for rapid development, developmental threshold, and optimum temperature for high adult weight were higher for the Australian populations than for North American populations, but these differences do not reflect adaptation to different environmental temperatures. We conclude that Australian populations of A. pisum did not originate in North America.
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