Character displacement or priority effects: immigration timing can affect community assembly with rapid evolution

Understanding how biological communities assemble in the presence of rapid evolution is becoming an important topic in ecology. Previous studies demonstrated that community assembly can be affected by two types of eco-evolutionary dynamics: evolution-mediated priority effect (EPE) and ecological character displacement (ECD). In EPE, early-arriving species prevent colonization of late-arriving species via local adaptation (i.e. community monopolization), whereas ECD promotes species coexistence by niche partitioning. Researchers tended to discuss the two processes separately, but it should be possible for those processes to operate in the same system depending on various conditions. Here, we developed a theoretical framework that integrates the two processes by using a simple two-species competition model with eco-evolutionary feedback. We revealed that, when an early-arriving species evolves, the difference in immigration timing between the early-arriving and a late-arriving species can be a key parameter. When the difference is small, ECD occurs because insufficient local adaptation of the early-arriving species allows colonization of the late-arriving species. When the difference is large, however, EPE occurs because niche pre-emption by local adaptation of the early-arriving species prevents colonization of the late-arriving species. Further theoretical and empirical studies will be important to better understand eco-evolutionary community assembly with ECD and EPE.