In ecology, a priority effect refers to the impact that a particular species can have on community development as a result of its prior arrival at a site.
[citation needed] Studies indicate that both abiotic (e.g., resource availability) and biotic (e.g., predation) factors can affect the strength of priority effects.
[1] In this sense, succession theory implicitly recognized priority effects; the prior arrival of certain species had important impacts on future community composition.
This static view of priority effects remained essentially unchanged by the concept of patch dynamics, introduced by Alex Watt in 1947.
The Initial Floristic Composition model was put forward by Frank Egler to describe community development in abandoned agricultural fields.
[5][6] Theorists argued that historical context could play a central role in determining which stable state would be present at any given time.
[7] In 1975, Jared Diamond[11] developed quantitative "assembly rules" to predict avian community composition on an archipelago.
Although the idea of deterministic community assembly initially drew criticism,[12] the approach continued to gain support.
Other modelling studies suggested that priority effects may be especially important when invasion frequency is low enough to allow species to become established before replacement,[15] or when other factors that could drive assembly (e.g., competition, abiotic stress) are relatively unimportant.
Robinson and Dickerson (1987) found that priority effects were important in some cases, but suggested, "Being the first to invade a habitat does not guarantee success; there must be sufficient time for the early colonist to increase its population size for it to pre-empt further colonization.
"[20] Robinson and Edgemon (1988) later developed 54 communities of phytoplankton species by varying invasion order, rate, and timing.
[21] These studies indicate that priority effects may not be the only or the most important historical factor affecting the trajectory of community development.
[25] Studies on larval insects and frogs in water-filled tree holes and stumps found that abiotic factors such as space, resource availability, and toxin levels can also be important in mediating priority effects.
The authors of the various studies attributed the prevalence of exotic grasses in California to the low seed production and relatively poor dispersal ability of native species.
Theoretical models have described cyclical assembly dynamics in which species associated with different suites of predators can repeatedly replace one another.
[40] Aggregation during recruitment and establishment could allow inferior competitors to coexist with or even displace competitive dominants over the long-term.
Several modelling efforts have begun to examine the implications of spatial priority effects for species coexistence.
[31] Moreover, although past studies focused on a small subset of species, recent papers indicate that priority effects may be important for a wide range of organisms, including fungi,[44][45] birds,[46] lizards,[47] and salamanders.