Detecting Ecological Trade-offs Using Selection Experiments

Theories of the evolution of niche breadth usually depend on the assumption that genotypes that are well adapted to exploit one habitat or resource are not well adapted to others. Such ‘‘trade-offs’’ are often apparent in interspecific comparisons, but have been harder to document at the within-population level. Selection experiments provide a promising means for detecting within-population trade-offs: if selection for adaptation to one environment (e.g., diet, host, temperature) reproducibly lowers fitness in another, trade-offs are the likeliest explanation. Here, I describe strategies for using selection experiments to detect ecological trade-offs and discuss some of the ambiguities that can arise in interpreting the results of such experiments. I also review two sets of studies that found evidence for trade-offs using selection experiments.