Strange intruders are invading our part of the world, threatening our environment and our economy. These newcomers and their impact on our ecological balance are the focus of Invasion Ecology , a new book that teaches students to investigate the behaviors of nonnative and native species. Studying real-life invaders such as purple loosestrife and Phragmites, students will learn about the links between biology and ecology -- and explore how scientists are fighting these aggressors with biological controls.