Genotype-environment interactions across ecologically important environment gradients: linking classical and molecular genetics

The environmental conditions experienced by wild populations vary in time (for instance, differences between years, or months) and space (for example differences between patches of habitat). We know that when different individuals experience different environments it creates differences in physical or behavioural attributes (phenotype). However, individuals may also experience the same environmental variation throughout their life but may still produce different phenotypes, and we have far less understanding of the implications of these differences for the way in which evolution occurs. Understanding these differences is important because natural selection is a phenomenon that acts upon individuals, whereby those individuals whose phenotypes are better able to exploit the environment produce more offspring, and therefore pass more genes onto the next generation. If the phenotypic attributes which enable individuals to best-exploit the environment are inherited, then evolution is expected to occur, and overall the population is expected to become better adapted to the environment. However, environments are constantly changing and this has consequences for our expectations of evolutionary change, which remarkably are little understood. Firstly, if individuals differ in their ability to exploit different environments and this reflects genetic differences, then the value of an individual's phenotype may change relative to the phenotype of other individuals, and subsequently different genes may underlie the phenotype favoured (and most successful) in different environments. Secondly, natural selection may favour different phenotypic attributes in different environmental conditions. This means that the environment may determine both the genetic basis underlying a particular phenotype, and the way in which natural selection acts upon phenotypes, and thus can influence which genes are passed to the following generation. We know almost nothing about how this process works, but it may help to explain why we often observe natural selection acting on heritable phenotypic traits but rarely see any genetic change in wild populations. I will further our understanding of the influence of variable environments on the evolutionary dynamics (the pattern of genetic change in response to natural selection) of quantitative traits (those which are influenced by a large number of genes), by developing and applying novel statistical methods to examine the influence of spatial and temporal environments on the genetic relationships between phenotypic characters, and between phenotype and fitness (an individual's success at passing genes to future generations). To do this, I will use data from an exceptionally well-characterised wild population of birds - a population of great tits breeding at Wytham, near Oxford (UK). I will also aim to address the problem that at present, we know little about which genes influence phenotype in wild populations, whether the influence of these genes is constant across environments, or whether they are acted upon consistently by natural selection across environments. To do this, I provide an exciting and innovative approach which exploits new developments in molecular genetics in order to dissect the effects of the environment at the level of the genome (across an individuals' full complement of genes). This will provide us with new insights into the way in which variable environmental conditions can create and maintain the diversity that we see in the natural world.