Sympatric speciation is most commonly observed in which group of organisms?

Sympatric speciation occurs when new species evolve from a single ancestral species while inhabiting the same geographic region. This process is commonly associated with certain groups of organisms that can exploit different ecological niches or utilize different reproductive strategies even when living in close proximity.

Plants exemplify this well due to mechanisms such as polyploidy, where chromosome duplication can lead to the formation of new species. For instance, a plant may reproduce asexually or through self-fertilization, allowing for genetic divergence while still being in the same location as its ancestors. This ability to undergo rapid changes and adaptations in reproductive methods makes plants particularly susceptible to sympatric speciation.

While birds, mammals, and insects can also experience speciation, they often do so through allopatric means, where a geographical barrier separates populations leading to divergence. Thus, plants provide a clear and representative example of sympatric speciation in action, resulting in the correct identification of this group for the question.