Understanding the interplay of evolutionary and ecological dynamics

Schoener, T. W. (2011). The newest synthesis: understanding the interplay of evolutionary and ecological dynamics. Science, 331, 426-429.

In this conceptual review, Schoener provides an introduction to the field of eco-evolutionary dynamics, which studies the reciprocal relationship between ecology and evolution. Historically, ecologists and evolutionary biologists have considered ecology and evolution as separate but related processes that operate on two separate time scales; the fast process (ecology) is observable, and changes in ecology affect the slow process (evolution). In contrast, eco-evolutionary dynamics considers that feedbacks may exist in both directions, in other words that ecology may be driven by evolution as well as vice versa. Introducing this simple two-directional link between ecology and evolution provides a new (complicating) angle for models and conception of ecology, since previous models could assume separation of time scales of the two processes without considering feedbacks between them.

Evidence for the potential effect of evolution on ecology comes primarily from observations that evolution can occur quickly. These observations are particularly notable in the modern world, where human alterations to the environment (e.g. through species introductions or extinctions from human predation) have allowed us to observe evolution occurring at a faster time scale than ever before. The existence of such rapid evolution means that the time scales of ecological and evolutionary dynamics may not be so different, allowing them to affect one another more directly. For instance, changes in genetic makeup of a population could affect its birth rates (an evolutionary effect on ecology), rather than differential birth rates affecting genetic makeup (an ecological effect on evolution). Despite these conceptual possibilities, Schoener concludes that there is very little direct experimental evidence to support the existence of eco-evolutionary dynamics. One of the few examples showed that different genetic crossings of the same species of stickleback (Gasterosteus aculeatus) affected ecology (e.g. productivity) differently, showing that evolution has the potential to affect ecology, even if in an experimental setting where genetic variation is artificially imposed. Overall, he proposes that more studies are needed, in particular those that track both genetic and ecological variables over multiple generations.