Question

The reinforcement hypothesis makes which specific “predictions” regarding divergent populations coming back into contact with one another? Are these predictions easily testable through observational studies?

Answer 1

What we can say is that the reinforcement hypothesis gives more idea to the evolution of increased reproductive isolation between hybridizing groups.  Because of this increased reproductive isolation, reinforcement plays an important role in speciation. So, the reinforcement that enhances divergence between species can create divergent populations. This hypothesis was first introduced by Howard in the year 1993. If reinforcement undergoes differently then it can initiate reproductive isolation between different sympatric populations. The observation that populations can diverge owing to differences in their interactions with heterospecifics is similar from other speciation models like ecological speciation, speciation mediated by sexual selection etc. This divergence between species shown parallel among populations that undergoes reinforcement and ancestral populations. It means that the trait divergence which can made reproductive isolation between species could also make similar levels of reproductive isolation within species. Thus, reinforcement hypothesis is a process that made speciation between already diverged groups.

Unfortunately, these predictions are not easily testable through observational studies.