Mark Kirkpatrick of the University of Texas at Austin will conduct studies of theoretical population genetics during the next five years using the funds granted by a Presidential Young Investigator Award. Dr. Kirkpatrick formulates genetic models of evolution and most recently he has been focusing on selective forces that relate to characters associated with one sex of animal or plant (hence the term, sexual selection). These traits are behavioral and morphological, and can affect mating success and survival within the contexts of a variety of social systems and environmental conditions. A second area of investigation pertains to the analysis of experimental data to determine if and how complex traits (or characters) are constrained by genetic and developmental mechanisms. Generally, Dr. Kirkpatrick's research contributions have been recognized for their sophistication and elegance, and this has led to his prominence and recognition.