Here's why:

* Sympatric speciation occurs when new species evolve from a single ancestral population while inhabiting the same geographic area.

* Reproductive isolation is the key to speciation. In this case, the plant population becomes reproductively isolated from its parent population despite living in the same area. This isolation could be due to various mechanisms like:

* Polyploidy: A change in the number of chromosomes, making them unable to interbreed with the original population.

* Habitat differentiation: The subpopulation may specialize in using a different niche within the same area, leading to reduced gene flow.

* Behavioral isolation: Changes in mating behaviors or preferences can prevent interbreeding.

Important Note: Sympatric speciation is generally considered less common than other forms of speciation (like allopatric speciation, where populations are geographically separated). However, it is an important process in the evolution of many plant and animal groups.