Seasonally varying populations of ectothermic insect taxa from a given locality are expected to cope with simultaneous changes in thermal and humidity conditions through phenotypic plasticity. Accordingly, we investigated effect of saturation deficit on desiccation resistance in wild caught flies from four seasons (spring, summer, rainy and autumn) and corresponding laboratory flies reared under season specific simulated thermal and humidity growth conditions. Summer flies showed about three times higher desiccation resistance and cuticular lipids compared with rainy season flies grown under simulated season specific thermal and humidity conditions. In contrast intermediate trends were observed for water balance related traits in flies reared under spring or autumn specific conditions but trait values overlapped across these two seasons. Further, a three fold difference in saturation deficit (an index of evaporative water loss due to combined thermal and humidity effect) between summer (27.5 mB) and rainy (8.5mB) season associated with two fold differences in the rate of water loss. Higher dehydration stress due to highest saturation deficit in summers is compensated by storage of higher amount of energy metabolite (trehalose) and cuticular lipids and these traits correlated positively with desiccation resistance. In Z. indianus, observed changes in desiccation related traits due to plastic effects of simulated growth conditions correspond to similar changes exhibited by seasonal wild-caught flies. Our result show that developmental plastic effects under ecologically relevant thermal and humidity conditions can explain seasonal adaptations for water balance related traits in Z. indianus and are likely to be associated with its invasive potential.
- Received March 29, 2016.
- Accepted August 5, 2016.
- © 2016. Published by The Company of Biologists Ltd