Hypothesis are testable meaning you are able to preform an experiment to see the relationship between two variables.
When a lineage splits into multiple line of descents, then, it leads to speciation. It is a process by which a single population evolves into different species. The process of speciation leads to the development of two or more species as the lineages are splitted. These two evolved species are genetically independent.
Hence, the blank can be filled with 'speciation'.
The new species would try and crossbreed possibly, or see them as weak and kill them off and take their resources.
