A successful invasive species can cause important changes in the functioning of an ecosystem. However, "ghost" species (ones that fail to establish themselves in a community) might still have significant effects on the ecosystem. For example, during transient invasion attempts, they can outcompete other species. In the simplified case of two competing resident species and one invading species only two results are possible: depending on the time of invasion and on the starting density of the invader, either one resident species or all three species survive.
This Demonstration models the interaction between three species, , , , with the differential equations of the standard Lotka–Volterra competition model. All species have the same carrying capacity but differ in growth rates. The competition coefficients are set in order to create the following interactions: and coexist in the absence of (Snapshot 1), outcompetes in absence of (Snapshot 2), is outcompeted by in the absence of (Snapshot 3). is treated as an invasive species.
You can vary the point of invasion on the time axis and the population size at the time of invasion. You can also vary the starting population sizes and at .
The outcome of competition of all three species depends drastically on the time of invasion: with early invasion outcompetes but is then eliminated by (Snapshot 4); a late invasion results in a coexistence of all three species (Snapshot 5) but a higher starting population size of the invader can act like an early invasion, so that finally only survives (Snapshot 6).