Modeling of priority effects and species dominance in long Island Sound benthic communities

Spatially structured communities are common in many systems, including the marine benthos where sessile species compete for substrate. Which species colonizes a habitat first may determine species coexistence or dominance. The strength of this priority effect will vary as a function of the interaction between life history processes and disturbance events at different spatial and temporal scales. On a local scale, disturbance tends to open up space, allowing new propagules to arrive, while on a regional scale, it has the potential to reduce source populations and the colonization ability of dispersal- limited species. Differences in larval longevity will have a direct influence on dispersal distance, the relative timing of colonization, and the impact of priority effects, especially when interacting with different disturbance regimes. This study presents a modeling exercise to highlight this synergy and its implications for invasive species and ecosystem management. Four life histories were simulated, representing species from the 4 common community states of Long Island Sound, USA: resident bryozoans, invasive ascidians, mussels, and the ascidian Diplosoma listerianum that is restricted to years with abnormally warm winters. Brooding species took longer to exert dominance than broadcast spawners, but were more resilient to disturbance, having less local extinctions. Simulations showed that the combined effects of dispersal ability and disturbance could allow the maintenance of diversity on a regional scale regardless of the identity of locally dominant species. Priority effects are only present when the system experiences localized disturbance regimes, such as predation.