Evolution of phenotypic plasticity and environmental change

Summary Charles Darwin's theory of natural selection lies at the centre of evolutionary studies and is particularly relevant today because of the threat posed to species by climate change. Species have evolved by natural selection in environments that have generally changed more slowly than those we are witnessing now and are predicting to experience over the coming decades. The main concern is that the process of natural selection will not be sufficiently rapid to enable populations to adapt to current rapid changes resulting in species that are not equipped to survive in the novel climates, causing a reduction in numbers or even extinction. Natural selection is a phenomenon that acts on individuals, whereby those whose phenotypes (i.e. their physical and behavioural attributes) that are better equipped to exploit environmental conditions will produce more offspring and therefore pass more genes on to the next generation. However, there is a second mechanism by which species can adapt to environmental change that operates within individuals. Individuals may show flexibility in their phenotype in relation to environmental change, a phenomenon known as phenotypic plasticity. A familiar example is the timing of egg laying in birds: individual females adjust their timing each year to coincide with the seasonal peak in food availability. Thus, species may be able to adapt to environmental change simply because individuals adjust relevant aspects of their phenotype. However, these within-individual adjustments alone may also not be sufficient in safeguarding populations from rapid change. It may be necessary for the two phenomena, natural selection and phenotypic plasticity, to work in tandem. This could operate if individuals vary in their phenotypic plasticity, and those individuals that show greater flexibility may have an advantage over those that do not. Thus, in the timing of egg laying example, females that are more flexible will be able to coincide with the peak availability more successfully and therefore produce more offspring than females who do not change. This would result in natural selection for plasticity. If the plasticity of the more flexible individuals is coded in their genes then the population may have the capacity to adapt to rapid climate change. The evolution of phenotypic plasticity in wild populations is a relatively new subject. However, it is critically important to study because it may be a key method by which populations can protect themselves from the potentially damaging effects of the rapid environmental changes that we are seeing today. A greater understanding of the evolution and ecology of phenotypic plasticity will be of interest to evolutionary biologists, population ecologists and behavioural ecologists. However, this work will also benefit conservation and the general public. I will carry out the work on a species of seabird, the European shag, which is currently under threat from human-induced environmental change, principally climate change. Shags are an ideal study species for research on phenotypic plasticity in the wild. However, it is important that we study seabirds for two other reasons. First, they are charismatic species with wide appeal, being some of the most familiar and spectacular sights on visits to the coast. Second, since they are positioned at the top of the food chain, their survival and breeding performance is linked to the abundance of species at lower trophic levels (e.g. fish, plankton). Thus, they offer a reliable, cost-effective monitor of the health of the marine environment. As such it is vital to understand the potential impact of anthropogenic change on their well being.