Molecular markers have opened exciting new windows through which to view the natural biological world. This treatment addresses the many applications for genetic markers (from polymorphic proteins and DNA) from the perspectives of population biology, behavioral ecology, organismal evolution, and phylogeny. Opening chapters review the history and purview of molecular approaches, and compare and contrast various laboratory techniques for revealing molecular markers. Subsequent chapters review the extensive scientific literature of molecular ecology and evolution, and describe a cornucopia of captivating discoveries about nature's workings, past and present.