Where’s the trade-off? Plasticity of development in response to degree of environmental variability in Aedes albopictus

In mosquitoes, sexually dimorphic trade-offs occur in development time versus mass at eclosion (males sacrifice mass for shorter development times whereas females maximize mass but take longer to develop). Aedes albopictus is an important invasive species and vector of several arboviruses. Because Aedes albopictus overwinters as diapausing eggs, larvae or adults that experience unfavorable conditions (e.g., freezing) die, and thus larvae might be expected to show developmental plasticity, accelerating development in response to a seasonal constraint of approaching winter. This plasticity is expected to be more pronounced where winters are more severe; degree of severity is correlated with photoperiod across latitudes. We conducted a laboratory experiment wherein we compared mass and development time of four populations of Ae. albopictus under three photoperiods (long, short stable, short declining). Populations were obtained from along a latitudinal gradient predicted to correlate with winter severity (Florida, North Carolina, Virginia, New Jersey). We predicted mild climates relatively free of winter freezing (Florida) would result in relatively low plasticity in response to simulated seasonal photoperiods, whereas areas with high winter severity (New Jersey) would show strong plastic responses. Contrary to our predications there were no differences among populations in response to photoperiods. Females from all locations were larger and took longer to develop under long versus short or declining photoperiods; individuals from northern populations were larger and developed more slowly. Mass-development trade-offs in Ae. albopictus are thus flexible in response to photoperiod, but populations do not appear to vary as a function of winter severity.