Effects of maternal and offspring environmental conditions on growth, development and diapause in latitudinal yellow dung fly populations

Abstract

Extensive phenotypic plasticity can allow populations to persist in changing environ- ments. Maternal effects represent one important but often neglected source of phenotypic plasticity. Mothers and offspring of 2 high- (northern Norway and central Sweden) and 2 low- (northern and southern Spain) latitude yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae) popula- tions were exposed to cold (12°C) and warm (18°C) temperatures and to short (8 h light:16 h dark) and long (16 h light:8 h dark) photoperiods in a fully blocked, split-brood common garden design of 8 treatment combinations. We also considered the role of energy content and size of the eggs in pro- ducing cross-generational maternal effects on offspring diapause, development time and growth rate. The incidence of diapause strongly declined towards the south, and the northernmost popula- tion grew and developed faster in response to perceived seasonal time constraints. There was strong population-specific phenotypic plasticity of all traits in response to offspring temperature and, more weakly, to offspring photoperiod, indicating a genetic basis of plasticity as well as genetic differenti- ation among populations. There were additional subtle cross-generational maternal effects exerted primarily by the lipid content of the eggs, largely independent of maternal treatment and population. Phenotypic plasticity of life-history traits in the yellow dung fly is predominantly influenced by the growing conditions during larval development, but populations can also respond to changing envi- ronments via trans-generational maternal effects.