Is phenology evolving in response to climate change?

Many aspects of the natural world are changing under climate change. One of the most notable is that the timing of natural events - phenology - is changing, with many species becoming earlier in their activities each year. How are they doing this? There two main mechanisms: short-term reactions to circumstances within the lifetime of an individual, known as plasticity, and genetic change across generations due to natural selection, i.e. evolution. The role played by each of these mechanisms is important, because they enable different rates of response and have different potential for sustained change. For example plasticity can generate a very fast response, but species have limits to plasticity, whereas genetic change is slower but may be sustained over time. To date the most detailed studies of phenology change focus on egg lay dates in birds which must have an ample food supply to raise chicks and in which there is a sharp spring peak in food abundance. These studies conclude that the birds respond plastically to cues such a temperature that indicate there will soon be food, while there is little evidence of evolutionary change. But many species with different kinds of life history, most notably mammals that store nutrition and have a gestation period, are changing phenology just as fast as birds. Since they cannot fine-tune birth dates to conditions at birth, evolution is likely to be a more important mechanism in these species. In the individually-monitored red deer on Rum, several aspects of phenology have got earlier over time. For example calving date has got earlier by 14 days since 1980, and there is pilot evidence this is due to a combination of genetic change and plasticity. In this study we will investigate eights phenology traits by (1) Measuring plasticity to a range of weather and biological drivers (such as food availability and parasites); (2) Measuring natural selection and testing the hypothesis that selection favouring earlier phenology has strengthened with warming temperatures; (3) Predicting and measuring the evolutionary (by which we mean genetic) response to selection; (4) Predicting the population implications of changing phenology.