A pioneer species in a series of succession is commonly an r-selected species that has the specific characteristics to establish itself in a newly available space. If the Facilitation model of succession is followed, the pioneer species does not only successfully establish an area but also modifies the environment in such a way that it becomes suitable for species of future successional stages. Common pioneer species include bacteria, mosses, fungi, and lichens because they are able to break down rocks which makes it easier for species of later successional stages to reach the nutrients in the ground.