Current climate change is characterized by an increase in weather variability, which includes altered means, variance and predictability of weather parameters, and which may affect an organism’s ecology and evolution. Few studies experimentally manipulated the variability of weather parameters, and very little is known about effects of changes in the intrinsic predictability of weather parameters on living organisms. Here we experimentally tested effects of differences in intrinsic precipitation-predictability on two herbaceous plants (Onobrychis viciifolia and Papaver rhoeas). Lower precipitation predictability led to phenological advance and to an increase in reproductive success, and population growth. Both species exhibited rapid transgenerational responses in phenology and fitness-related traits across four generations that mitigated most effects of precipitation-predictability on fitness proxies of ancestors. Transgenerational responses appeared to be the result of changes in phenotypic plasticity rather than local adaptation. They mainly existed with respect to conditions prevailing during early, but not during late growth, suggesting that responses to differences in predictability during late growth might be more difficult. The results show that lower short-term predictability of precipitation positively affected fitness, that rapid transgenerational responses existed, and that different time-scales of predictability (short-term, seasonal, and transgenerational predictability) may affect organisms differently. This shows that the time-scale of predictability should be considered in evolutionary and ecological theories, and in assessments of the consequences of climate change.

Many color ornaments are composite traits consisting of at least four components, which themselves may be more complex, determined by independent evolutionary pathways, and potentially being under different environmental control. To date, little evidence exists that several different components of color elaboration are condition-dependent and no direct evidence exists that different ornamental components are affected by different sources of variation. For example, in carotenoid-based plumage coloration, one of the best-known condition-dependent ornaments, color elaboration stems from both condition-dependent pigment concentration and structural components. Some environmental flexibility of these components has been suggested, but specifically which and how they are affected remains unknown. Here we tested whether multiple color components may be condition-dependent, by using a comprehensive 3 x 2 experimental design, in which we carotenoid supplemented and immune challenged great tit nestlings (Parus major) and quantified effects on different components of coloration. Plumage coloration was affected by an interaction between carotenoid availability and immune challenge. Path analyses showed that carotenoid supplementation increased plumage saturation via feather carotenoid concentration and via mechanisms unrelated to carotenoid-deposition, while immune challenge affected feather length, but not carotenoid concentration. Thus, independent condition-dependent pathways, affected by different sources of variation, determine color elaboration. This provides opportunities for the evolution of multiple signals within components of ornamental traits. This finding indicates that the selective forces shaping the evolution of different components of a composite trait and the trait’s signal content may be more complex than believed so far, and that holistic approaches are required for drawing comprehensive evolutionary conclusions.

No description available