In this article I generalize ecological theory by developing the notion of separate but linked ecologies. I characterize an ecology by its set of actors, its set of locations, and the relation it involves between these. I then develop two central concepts for the linkage of ecologies: hinges and avatars. The first are issues or strategies that "work" in both ecologies at once. The second are attempts to institutionalize in one ecology a copy or colony of an actor in another. (...) The article investigates the first of these concepts using two detailed examples of hinge analysis between the professional and political ecologies. Both concern medical licensing, the first in 19th-century New York and the second in 19th-century England. For the avatar concept, the article analyzes four less detailed cases linking the professional and university ecologies: computer science, criminal justice, clinical psychology, and applied economics. (shrink)