Final answer:
Speciation is the process through which new species arise, with allopatric and sympatric speciation being two pathways. The scenario described refers to parapatric speciation, where two populations with overlapping ranges evolve into distinct species despite some interbreeding. This is a middle ground between allopatric speciation, characterized by geographical separation, and sympatric speciation, which occurs within a shared habitat without physical separation.
Step-by-step explanation:
Speciation refers to the process through which new species arise from a single ancestral species. This can occur through various mechanisms, which are broadly categorized into allopatric speciation and sympatric speciation. Allopatric speciation involves geographic separation of populations from a parent species and subsequent evolutionary changes that lead to reproductive isolation. Sympatric speciation occurs without geographic separation but through reproductive isolation mechanisms within a shared habitat.
Addressing the question: Two populations occupy overlapping ranges, so a limited amount of interbreeding occurs. This situation is indicative of parapatric speciation. Although parapatric speciation was not defined in the provided reference material, it falls between allopatric and sympatric speciation. In parapatric speciation, two populations are partially isolated but not completely seperated geographically, which allows for some interbreeding. However, individuals are more likely to mate within their own population, leading to divergent evolution and the potential for speciation if reproductive isolation mechanisms develop.
The example of the northern spotted owl and the Mexican spotted owl along the west coast of the United States shows allopatric speciation, where geographic features such as glaciers could have caused initial separation. In contrast, sympatric speciation can occur through mechanisms such as polyploidy within a shared habitat and without any physical separation, although it is considered less common.