Genetic correlations and reaction norms in wing pattern of the tropical butterfly Bicyclus anynana

Abstract

Genetic correlations (rg) within and across environments, were determined in the tropical, dry-wet seasonal polyphenic butterfly Bicyclus anynana, over four temperatures, for larval DEVELOPMENT time (plastic), pupal WEIGHT (less plastic) and two wing pattern characters: SEASONAL FORM (plastic) and THERMAL FORM (less plastic). The rgs for SEASONAL FORM were weak, making it relatively independent across seasons. The rgs for WEIGHT were intermediate between THERMAL and SEASONAL FORM. Negative rgs were present for DEVELOPMENT. The reaction norms for DEVELOPMENT time clearly crossed at an intermediate temperature, whereas the others did not. This implies that selection for fast growers in one season has an opposite effect in the other season. rgs between WEIGHT and the other characters remained constant over temperatures, as did the correlation between DEVELOPMENT and THERMAL FORM. Both the correlation between DEVELOPMENT and SEASONAL FORM and between THERMAL FORM and SEASONAL FORM showed a sign change across temperatures. Reaction norms confirmed and clarified these sign changes. The sign change for DEVELOPMENT-SEASONAL FORM might reflect underlying physiological processes. The sign change for THERMAL FORM-SEASONAL FORM might be caused by different trade-offs in the different seasons.