All else being equal, selection should more strongly favor reinforcement of reproductive isolation among related species in: peripatric populations over sympatric populations. peripatric populations over allopatric populations. allopatric populations over peripatric populations. allopatric populations over sympatric populations. sympatric populations over allopatric populations.

sympatric populations over allopatric populations.

Explanation:

Allopatric speciation is a form of speciation (creation of new species) that occurs as a result of geographic isolation. This means that a part of population becomes physically separated from the initial main population. There is no gene flow between these two populations and as a result the two populations  reach a high level  of genetic divergence. They can no longer interbreed which means they become two different species (speciation).

New populations evolve as result of mutation, genetic drift and natural selection.

Sympatric speciation is a form of speciation without geographic isolation, usually due to  the reproductive isolation or changes in the chromosomes of the organism.