Final answer:
Adaptive radiation typically occurs due to the absence of competition for ecological resources or through island colonization, not due to increased gene flow between species.
Step-by-step explanation:
The question concerns hypotheses about the conditions that can lead to adaptive radiation. Regarding the options provided, adaptive radiation is often the result of the absence of competition for ecological resources, which may happen because of a new habitat, ecological niches, or after a mass extinction clears ecological roles and allows a species to diversify to fill those roles. It is also associated with island colonization, where a founder species can diversify into multiple new species as seen in the example of the Hawaiian honeycreepers.
The option that does not align with typical causes of adaptive radiation is increased gene flow between species. Increased gene flow tends to homogenize genetic differences rather than promote speciation. Therefore, the correct answer is that option 3, suggesting adaptive radiations occur as a result of increased gene flow between species, is not a hypothesis about the conditions that can lead to adaptive radiation.