Question

homework - mechanisms of speciation
in which situation will populations experience gene flow?
hybridization between two populations of ground beetles
natural - selection pressures between two populations of dragonflies
mate competition between two populations of red - legged grasshoppers
intersecting migration routes between two populations of monarch butterflies

Explanation:

Gene flow is the transfer of genetic material from one population to another. Intersecting migration routes between two populations of monarch butterflies would allow for the exchange of genes as individuals from one population can move and breed with individuals from the other population. Hybridization (if the two ground beetle populations are different species, it may not be valid gene flow as species barriers might exist in a strict sense), natural - selection pressures (more about differential survival and reproduction within a population or between populations in terms of trait selection, not direct gene transfer), and mate competition (about reproductive success within a population or between populations for mates, not gene transfer) are not the main mechanisms of gene flow.

Answer:

intersecting migration routes between two populations of monarch butterflies