Why can reproductive isolation lead to speciation?

Reproductive isolation is a key mechanism in the process of speciation, which refers to the formation of new and distinct species in the course of evolution. One of the primary ways that reproductive isolation contributes to speciation is by reducing gene flow between populations.

When populations of the same species become reproductively isolated, whether through geographic barriers, behavioral differences, temporal changes in mating seasons, or other mechanisms, the exchange of genetic material between them diminishes or ceases entirely. Over time, this lack of gene flow allows the isolated populations to diverge genetically due to different selective pressures, genetic drift, or mutation. As these populations adapt to their distinct environments or ecological niches, they accumulate differences that can eventually lead to the emergence of new species.

In this context, the reduction in gene flow is crucial because it allows for the independent evolution of populations without the homogenizing influence of interbreeding. This evolutionary divergence is fundamental to the process of speciation. In contrast, options that mention increasing genetic diversity, promoting hybridization, or eliminating natural selection do not accurately reflect the central role that reproductive isolation plays in facilitating the development of distinct species.