Environmental colour affects aspects of single-species population dynamics

Single-species populations of ciliates (Colpidium and Paramecium) experienc ed constant temperature or white or reddened temperature fluctuations in aq uatic microcosms in order to test three hypotheses about how environmental colour influences population dynamics. (i) Models predict that the colour o f population dynamics is tinged by the colour of the environmental variabil ity However, environmental colour had no effect on the colour of population dynamics. All population dynamics in this experiment were reddened, regard less of environmental colour. iii! Models predict that populations will cra ck reddened environmental variability more closely than white environmental variability and that populations with a higher intrinsic growth rate (r) w ill track environmental variability more closely than populations with a lo w r. The experimental populations behaved as predicted. (iii! Models predic t that population variability is determined by interaction between r and th e environmental variability. The experimental populations behaved as predic ted. These results show that (i) reddened population dynamics mall need no special explanation, such as reddened environments, spatial subdivision or interspecific interactions, and (ii) and (iii) that population dynamics are sensitive to environmental colour, in agreement with population models. Co rrect specification of the colour of the environmental variability in model s is required for accurate predictions. Further work is needed to study the effects of environmental colour on communities and ecosystems.