The first species that colonizes new or undisturbed land is called a species.

The first species that colonizes new of undistributed land is called as pioneer species, or simply pioneers. If you check the meaning of pioneer, it's a type of person or entity that became the first to explore or exploit a certain something. In this case, they were the first species who explores the lands to create a society.

When you are making a guess you are forming a hypothesis