Ecology in Action

Dan Janzen and Winnie Hallwachs, his wife and colleague, have spent two lifetimes studying ecological interactions between organisms, mostly at Area de Conservacion Guanacaste (ACG) in northwestern Costa Rica. Early in his career, Janzen investigated many basic questions in evolutionary community ecology. One study of plant reproductive success and life history strategies showed that legume species use one of two alternative strategies to reproduce successfully – producing huge numbers of tiny defenseless seeds or small numbers of large, well-defended seeds. A second study explained high biological diversity in rainforests as arising because baby plants survive poorly near their parents (because seed predators consume them there), and only become established a considerable distance away from them. He also emphasizes that current selection pressures may differ from historical pressures, so it is critical to understand ecosystems in the context of their evolutionary history. Both Janzen and Hallwachs have now shifted their focus to inventorying the diversity of Lepidoptera, their parasitoids and host plants at ACG, so that their complex interactions can be understood by researchers and by students who use ACQ as a natural classroom.