Residence time: An overlooked constraint on community assembly and structure
Much of Earth’s biological diversity is found within environments that flow or physically turnover. In these environments, the amount of time that individual particles remain in the system (i.e. residence time) should influence the assembly and structure of ecological communities. Too little time, and individuals may die or emigrate before reproducing. Too much time, and populations may grow until they exhaust resources. While the influence of residence time on growth and biomass is well-understood in simplified experimental microcosms, its influence on diversity-related aspects of ecologically and spatially complex communities is rarely investigated. We used a combination of individual-based modeling and computational fluid dynamics to simulate the life history of individuals belonging to species that vary in life history traits, where both individuals and resources flow through a spatially explicit environment.
A benefit of individual-based modeling is the potential for combinations of traits to arise serendipitously. At the extremes, where turnover or flow is rapid or slow, residence time acted as a filter, selecting against trait combinations that prevent populations from maintaining viable populations. In general, residence time constrained compositional turnover, community size, and taxonomic richness, which in turn, constrain the distribution of traits and abundance among taxa. Residence time should be considered a primary constraint-variable, the influence of which, should be investigated in ecological communities and incorporated into biodiversity theory.