Species loss leads to community closure

Global extinction of a species is sadly irreversible. At a local scale, how ever, extinctions may be followed by re-invasion. We here show that this is not necessarily the case and that an ecological community may close its do ors for re-invasion of species lost from it. Previous studies of how commun ities are assembled have shown that there may be rules for that process and that limitations are set to the order by which species are introduced and put together. Instead of focusing on the assembly process we randomly gener ated simple competitive model communities that were stable and allowed for two to 10 coexisting species. When a randomly selected single species was r emoved from the community, the cascading species loss was recorded and freq uently the resulting community was more than halved. Cascading extinctions have previously been recorded, but we here show that the relative magnitude of the cascade is dependent on community size land not only trophic struct ure) and that the reintroduction of the original species lost often is impo ssible. Hence, species loss does not simply leave a void potentially refill ed, bur: permanently alters the entire community structure and consequently the adaptive landscape for potential re-invaders.