All organisms live in a fluid medium (either air or water), and are therefore subject to the physics of fluids. In particular, all plants and animals encounter fluid-dynamic forces that can potentially injure or dislodge the organism, thereby adversely affecting its survival, and in many cases fluid-dynamic forces are thought to have acted as selective factors in the evolution of body form. Aspects of these forces (e.g., drag on benthic organisms, lift on the wings of birds and insects) have been extensively studied, and our understanding of their mechanism has been an important tool in interpreting the ecology and evolution of these groups. Despite the importance of fluid-dynamic forces, one common force, near-wall lift, has escaped notice. Near-wall lift is likely to be an important source of mortality in many benthic marine animals. For instance, limpets and keyhole limpets are often killed when dislodge by hydrodynamic forces, and near- wall lift is by far the largest force acting on them. However, the mechanism of near-wall lift and its interaction with body form have never ben examined and are not well understood. These investigations by Dr. Denny have three major goals: (1) To understand the mechanism of near-wall-lift and thereby to provide a firm basis for exploring its role as a source of mortality in limpets and keyhole limpets. (2) To measure the strength distribution of limpets and keyhole limpets, thereby allowing for the quantitative prediction of rates of mortality as a function of the local wave regime. (3) To quantitatively predict the selective advantage or disadvantage in wall lift to act as an agent of selective mortality. As such, this research provides a quantitative, experimental tool for exploring the role fluid-dynamic forces play at the crucial nexus of community ecology, population biology, and the evolution of body form.
