Body size and wing shape responses of mosquitoes (Diptera: Culicidae) to contrasting environmental conditions in cold-temperate Argentine Patagonia.

Abstract

Insect adaptations to seasonal environmental variation reveal diverse responses, including changes in morphology and ecophysiology, which may influence life-history traits during immature and adult stages. The objective of the present study was to evaluate the relative body size and wing shape in adult Culex (Culex) brethesi Dyar mosquitoes (Diptera: Culicidae) emerging from larvae reared under contrasting environmental conditions in Patagonia, Argentina (Aldea Escolar, Chubut Province). Two field experiments were conducted during winter 2021 (winter larvae experiment, WLE) and summer 2022 (summer larvae experiment, SLE). Larval cohorts were monitored until adult emergence. Wing length and centroid size were estimated using linear and geometric morphometric approaches and used as proxies for relative body size. Wing morphology was analysed to characterize variation associated with larval developmental conditions. In addition, survival analyses were performed to assess differences in life-history traits between seasonal cohorts. Generalized linear mixed-effects models showed that females consistently had longer wings than males. The largest wing length values were recorded for WLE females, whereas male wing length was similar between WLE and SLE adults. For centroid size, significant main effects indicated that females and WLE individuals were larger. Wing shape analysis showed that summer individuals exhibited broader wings, whereas winter individuals had narrower wings. Among the environmental variables evaluated in this study, nitrate + nitrite, conductivity and pH emerged as significant predictors of adult body size. Overall, larvae from the winter cohort exhibited higher larval survival but substantially delayed adult emergence and produced larger adults with narrower wings. These differences may be associated with variation in dispersal capacity, reproductive performance and other fitness-related traits. Our findings improve the understanding of how environmental conditions experienced during larval development are associated with variation in mosquito morphology and life-history traits in cold-temperate environments and provide a baseline for future studies on population responses to environmental change.