Final answer:
Gene flow does not promote speciation because it involves the exchange of genetic material between populations, which reduces the chance of forming new species.
Step-by-step explanation:
The question revolves around the concept of what promotes or does not promote speciation, which is the process through which new genetically distinct species evolve. The answer to the question which of the following does NOT tend to promote speciation is gene flow. Gene flow refers to the transfer of genetic variation from one population to another. If there is gene flow between two populations, they are likely to share genetic material, which minimizes genetic differences and can prevent the formation of new species. On the other hand, disruptive selection, polyploidy (having more than two sets of chromosomes), and natural selection can all drive speciation by creating reproductive barriers or significant genetic differences within a population.