Early species may facilitate, inhibit or tolerate the arrival of other species.
Early species can promote the growth of later arrivals. For example: a pioneer species of lichens can break rocks and convert bare sand into fertile soil. This soil will make the way for growth of other organisms. The pioneer species may be wiped out if its not able to compete with the later arrivals.
Early species can also inhibit the growth of later arrivals by predating on them or competing with them for resources. For example: in many forest ecosystems shrub canopies are known to inhibit tree growth because they fight for the sunlight and do not let other plants germinate.
When early species tolerates new arrivals, it neither facilitates nor inhibits their growth. All these species can coexist.
