Recognizing patterns in nature and using these observations to generate and test hypotheses are fundamental components of scientific inquiry [1]. The science of ecotoxicology aims to identify patterns that describe population and community responses to contaminants. Our ability to predict these responses is generally greatest for communities that change consistently in response to a specific contaminant or class of contaminants, thereby providing a direct path to extrapolation, hypothesis testing, and scientific inference (see Predicting the Effects of Contaminants). Although evidence suggests that some communities respond similarly to both natural and anthropogenic stressors [2], we know that regional variation in how communities are composed as a result of environmental, historical, biogeographical, or climatic factors complicates our ability to identify general patterns. Several studies have reported that the effects of contaminants on populations and communities vary along environmental In This Issue:
ET&C FOCUSFocus articles are part of a regular series intended to sharpen understanding of current and emerging topics of interest to the scientific community.Abstract-Context dependency refers to variation in ecological patterns and processes across environmental or spatiotemporal gradients. Research on context dependency in basic ecology has focused primarily on variation in the relative importance of species interactions (e.g., competition and predation) among communities. In this Focus article, the authors extend this concept to include variation in responses of communities to contaminants and other anthropogenic stressors. Because the structure of communities varies naturally along environmental gradients, their responses to contaminants may also vary. Similar to the way in which aquatic toxicologists assess abiotic factors associated with contaminant bioavailability, observations about context dependency could be used to test hypotheses about ecological mechanisms responsible for differences in sensitivity among communities. Environ. Toxicol.