Final answer:
Reproductive isolating barriers are important in both allopatric and sympatric speciation. In allopatric speciation, geographic barriers play a role, but reproductive barriers ultimately allow speciation to occur. In sympatric speciation, reproductive barriers are even more critical as they are the primary means of speciation within a shared habitat.
Step-by-step explanation:
Importance of Reproductive Isolating Barriers in Speciation
Reproductive isolating barriers are crucial for the process of speciation, which is the formation of new and distinct species in the course of evolution. These barriers can exist in both allopatric and sympatric speciation scenarios. In allopatric speciation, populations are geographically separated, preventing gene flow, and over time, evolutionary changes accumulate leading to speciation. In contrast, sympatric speciation occurs without geographic separation, often through mechanisms such as polyploidy, where the presence of extra chromosomes can result in reproductive isolation within a shared habitat.
While geographic isolation in allopatric speciation is a significant barrier, it's the reproductive isolating barriers that ultimately allow for speciation to occur, by preventing interbreeding between populations that could otherwise continue to share genes. In sympatric speciation, these barriers are even more critical because the populations are not geographically separated, and other factors, such as behavioral differences or polyploidy, must act to separate the species reproductively.
Therefore, reproductive isolating barriers are important in both allopatric and sympatric speciation. However, in sympatric speciation, these mechanisms are the main driving force for the emergence of new species.