Pioneer species are those first species that colonize places where previously there were no living beings, like, for example, algae that colonize bare rocks. In general, pioneer species are autotrophs or those that maintain harmonious ecological interaction with autotrophic beings (like autotrophic bacteria, herbaceous plants, lichens).
The pioneer community is formed of species able to survive under hostile environments. The presence of these species modifies the microenvironment generating changes in abiotic and biotic factors of the ecosystem undergoing formation. Therefore they open the way to other species to establish in the place by the creation of new potential ecological niches.