Ecological Change

Conceptual Overview

Two sets of concepts are essential for understanding ecological change: first, the mechanisms of adaptation, and second, different types of adaptive outcomes. The progenitors of organizational ecology, Howard Aldrich, Michael Hannan, John Freeman, Glenn Carroll, Bill McKelvey, and others, all argue that adaptation occurs through variation, selection, and retention by constituent populations within a community. These classic mechanisms are now known not to operate in purely Darwinian terms, but to involve some degree of Lamarckian (learning-based) evolution. Variation, the creation of new methods or forms within a population, may occur intentionally, not just via random chance or experimentation. Institutional entrepreneuring through innovation, creative destruction, and the leveraging of intangible resources can create new models of organizing. Selection of various alternatives involves not just competition, but also cooperation and networked interdependence among population members. Innovations are often selected by networks of common interest or supportive social movements. Retention, the encoded preservation of new alternatives, can occur not only for highly individualistic, rational reasons, but also for less individualistic and rational ones. Hannan, Freeman, Carroll, and colleagues have convincingly shown that both competition and legitimacy pressure are at work in shaping this path and the survival of different population members.

The end point of evolution for a community is not knowable in advance. Nevertheless, evolution is path dependent, and there may be stable evolutionary points of ecological change based on a specific population or community's path. Stability may occur within a population once diffusion of an innovation has been taken up as a solution yet has not reached saturation point, e.g., when density dependence has reached a temporary equilibrium based on the joint effects of legitimacy and competition. Stability across populations may occur when there is some [Page 414]ordering principle by domain or level that serves the majority of subpopulations. For instance, resource partitioning may lead to a dual market structure where large generalists compete in the core and small specialists become located in the periphery. Stability of the whole may occur not only under different diffusion periods and new orderings of domains, but also when the community has reorganized to better utilize existing resources. For example, the existing workforce within an industry may have re-sorted into new employment models. Indeed, as Aldrich, Rickard Sandell, and others have argued, growth itself may not characterize community or population change along all evolutionary paths, a point echoed today by environmental ecologists.

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