The first species to colonize an area during ecological succession is called a

Pioneer species
he community begins with relatively few pioneering plants and animals and develops through increasing complexity until it becomes stable or self-perpetuating as a climax community. The "engine" of succession, the cause of ecosystem change, is the impact of established species upon their own environments. A consequence of living is the sometimes subtle and sometimes covert alteration of one's own environment.

Cells of an organism tell each other when predators are near.