Adaptation of the developmental process of Anaphes victus (Hymenoptera: Mymaridae) to local climatic conditions across North America

Abstract

Anaphes victus Huber (Hymenoptera; Mymaridae), an egg parasitoid of weevils (Curculionidae), has a North American distribution and displays genetic variability among populations from different locations. Local adaptation to temperature was compared among three A. victus ecotypes originating from different latitudes: Texas, Michigan, and Québec. Development occurred between 11.5 and 34.0°C for all ecotypes and was accurately described by sigmoid curves. Some adaptations of A. victus to local climatic conditions were found, because the Texas ecotype had a higher developmental rate at the temperature of maximal developmental rate (Tm) than both northern temperate ecotypes and it developed faster at high temperatures. In contrast, the ecotypes from Michigan and Québec displayed faster developmental rates at low temperatures. In contrast to the Texas ecotype, both northern ecotypes have Tm values above the average maximum temperatures of their original habitat. These results are discussed in the context of evolutionary constraint that could have restricted the adaptation of the developmental process in A. victus. Lower developmental thresholds were similar across ecotypes and sexes, an indication that this parameter may not be subjected to local adaptation. For each ecotype, males required fewer degree-days than females to complete their immature development.