Classically, it was thought that evolutionary processes occurred at a much slower pace than demographic/ecological processes. Nobody, ever thought about incorporating both processes into the same model as they were assumed to occur at different time scales. We slowly came to realize that this way of thinking is quite wrong and many demographic/ecological changes (demographic expansion for example) directly affect evolutionary processes and even more important that evolutionary processes can directly influence demographic/ecological processes. I take for example Kirkpatrick and Barton (1996) who investigated how dispersal load (fitness decrease due to maladaptive alleles brought to local populations by dispersal) affect the "evolution" of the species range limits.
Who (what) are the main authors (articles) that allowed for this switch in our viewpoint about the interrelations between evolution and demographic/ecological processes?
Dennis Chitty might have been an important author to establish the viewpoint that evolutionary processes can influence the probability of survival of a population. However, I know a little bit about his work only because he was professor at my department (way before I even arrived in the department) and he might therefore not be the most important author of all.