A major goal of assembly ecology is to understand how the sequence and timing of species affect the strength of species interactions. Towards this goal I have been developing a model system to study community assembly in coral reef fish communities (in collaboration with Shane Geange, Victoria U. Wellington, New Zealand). Colonization dynamics of reef fish is affected by stochastic larval supply driven by variable weather and ocean currents, which leads to high natural variation in the sequence and timing of species colonization. We have shown that the sequence of species arrival can alter the strength of competition and that increased separation in timing of species arrival can flip competitive dominance (i.e. a priority effect). My work on these priority effects has overturned the idea that random arrival of colonizers alone generates patterns of community structure. Rather, random arrival interacts with predictable interactions between species to generate distinct species assemblages occupying environmentally similar habitats
Most recently we have expanded our study of assembly dynamics to include predation, which has largely been ignored in the competition-centric community assembly literature. Most predation studies have focused on the effects of chronic predator exposure (i.e., presence-absence or a gradient of predator densities), however, predator migration, mortality, and recruitment can lead to spatio-temporal variability in predation pressure. Such variability can result in a mosaic of habitat patches with differing patterns of predator occupancy, mean predator density, and timing of predator arrival (relative to prey). Focusing on a common reef predator we have described variability in the density, patch occupancy duration, and relative sequence of predator and prey arrival. We factorially manipulated these idiosyncratic types of predator patch occupancy in the field to show that early and late arriving predators can produce unique community composition and biodiversity of prey communities. The effects of predator arrival timing are comparable to well-studied effects of predator density.
Stier A.C., Geange S.W., Holdo R., and M. Roy. Early Bird Gets the Worm: Coexistence of Inferior Competitors Through Separation in Sequence and Timing of Species Arrival. Intended for American Naturalist
Stier A.C., S.W. Geange‡, and K.M. Hanson. Predator intensity, frequency, and timing of arrival in reef fish communities. Ecology.
Geange S.W., J.S. Shima, and A.C. Stier. 2010. An evaluation of competitive effect and response in three species of coral reef fish. In press MEPS