Perhaps the most basic question about the process of speciation is whether or not it is an adaptive progress. Recent studies suggest that natural selection and adaptation may play a more significant role in the early stages of divergence and the evolution of reproductive isolation than previously thought. This ‘adaptive speciation’ may be particularly common where there is partial spatial separation between habitats, such as on the steep environmental gradients that characterize sea-shore habitats. Species living in these habitats are, therefore, excellent models for the study of adaptation and its contribution to speciation. Novel approaches based on genomic tools now make the genetic basis of adaptation and speciation more accessible than ever before. The overall goal of the proposed application is to increase our understanding of adaptive speciation. My model system will be the rocky shore gastropod Littorina saxatilis. This powerful model shows independent but similar responses to habitat gradients in different parts of Europe, with evidence of progression towards speciation. I will combine studies of morphological variation, using the latest methods of geometric analysis, with the population genomics approach, using AFLP markers, to dissect the genetic basis of adaptation and the role of morphological adaptation in the overall divergence between snail morphotypes. Furthermore, I will examine plastic responses to the environmental gradient and determine their contribution to adaptation. This project will provide me with a much enhanced suite of skills, including new laboratory and analytical skills in molecular ecology and population ge