Which factor is most commonly associated with sympatric speciation in plants?

Polyploidy is the primary factor commonly associated with sympatric speciation in plants. This process involves the duplication of chromosomes within an organism, which can create reproductive isolation without any geographical barriers. When a plant species undergoes polyploidy, it may arise as a new species that can no longer interbreed with its parent population due to differences in chromosome number. This mechanism allows for speciation to occur even when populations share the same habitat.

In the context of plant evolution, polyploid populations can exploit different ecological niches or resources, leading to further diversification. Unlike geographical barriers, which separate populations in allopatric speciation, sympatric speciation through polyploidy occurs in overlapping populations, emphasizing the role of genetic changes rather than physical separation in the emergence of new species.