Answer:
The connection is the common ancestors.
Step-by-step explanation:
As shown in the question above, Darwin's work generated a map where the lines and forks created an image similar to a tree.
This "tree" linked species and places studied by Darwin. This connection was established by a common connection to all the species that Darwin studied. This connection was the common ancestor that a set of species shared and that was essential for the evolution of species to be understood.