Ecological character displacement: glass half full or half empty?

Ecological character displacement (ECD), the evolutionary divergence of competing species, has oscillated wildly in scientific opinion. Initially thought to play a central role in community assembly and adaptive radiation, ECD recovered from a 1980s nadir to present-day prominence on the strength of many case studies compiled in several influential reviews. However, we reviewed recent studies and found that only nine of 144 cases are strong examples that have ruled out alternative explanations for an ECD-like pattern. We suggest that the rise in esteem of ECD has outpaced available data and that more complete, rather than simply more, case studies are needed. Recent years have revealed that evolutionary change can be observed as it occurs, opening the door to experimental field studies as a new approach to studying ECD.