Even a relatively small garden is a miniature ecosystem. It includes a surprising diversity of organisms that interact in a myriad of ways. Some are permanent residents, others come and go in search of a meal or a mate. An insect feeding on a garden plant is simultaneously hunted by predators and weakened by parasites; it competes with other herbivores for choice food plants; it is hindered in its feeding by the plants' chemical and physical defenses; and it challenges other members of its species for the best mates and locations for egg-laying. Ecologists Carroll and Salt argue that the more...