Thursday, August 5, 2010
Exhibit Hall A, David L Lawrence Convention Center
Intraspecific variation in life history across latitudinal gradients is a focus in ecology because climate variation with latitude can be a major selective force on life history traits of many organisms. Since A. albopictus invaded North America in the mid-1980s, it has spread across a range of »14ºC latitude. Populations at the latitudinal extremes of the distribution of A. albopictus experience different climates that likely provide strong selection on life history; however, a prior life-table experiment showed no consistent differences between northern versus southern populations in adult mortality and reproductive schedules. Prior research shows that female A. albopictus produce diapause eggs in response to short daylengths and that diapause eggs have higher survival during adverse winter conditions than developing offspring. We hypothesize that the primary response of North American A. albopictus to unfavorable climatic conditions may not involve quantitative variation in the allocation to reproductive output but rather via the phenotypically plastic alternative life history strategy of producing diapausing eggs rather than developing eggs. We conducted life-table experiments to compare the survival, longevity, and reproduction of A. albopictus from three northern (Springfield, IL; Tenton, NJ; Salem, NJ) and three southern populations (Tampa, FL; Palm Beach, FL; Palmetto, FL) under long (15:9 L:D) and short day-lengths (12:12 L:D) to test whether latitudinal differences in diapause affect survival and reproductive schedules.
Linear models indicated higher incidence of diapause eggs in all populations under short daylength compared to long daylength, but a significantly greater increase in northern populations compared to southern populations. We detected no consistent differences in reproductive output, numbers of bloodmeals, or longevity between northern versus southern populations or between daylengths. These results suggest the main response of A. albopictus to adverse climate conditions is via the phenotypically plastic strategy of producing diapause eggs rather than quantitative variation in allocation to reproduction, but that there is inherent latitudinal variation in the ability of females to express this life history strategy.