Even if a species makes it to a community and is able to tolerate its environmental conditions, it must be able to live with all the other species in that community. It must be able to obtain food, survive without being eaten, and cope with competitors. Thus whether a species is successful in a new community will depend on the presence of resident species that either promote or restrict species membership.

The ability of resident species to exclude or slow the population growth of non-native species is called biotic resistance. While there are a handful of studies showing that competitors and herbivores can slow down the spread of non-native plant species, confirmed examples of biotic resistance are few. Identifying whether biotic resistance is common in nature may reflect the fact that many failed introductions of non-native species go undetected. Nevertheless, the evidence from the invasive species literature suggests that the influence of resident species may be a fairly porous filter when it comes to restricting species from, or promoting species to, communities.