In a field of flowering plants known as evening primrose, a genetic doubling event produces a few individuals that are still in physical contact with each other, but they're reproductively isolated from the rest of the population. Thus, the exceptional plants are considered a new species. This type of speciation would be described as

sympatric

Explanation:

Speciation is the process by which new species originate and there are several mechanisms and processes by which speciation can take place.

When speciation occurs in a common geographical area where there are no barriers preventing the mating of species and the members of the species lie in close proximity to one another however, even in such conditions new species arise because of some differential characteristics. Such a speciation is termed as sympatric speciation.

In the given situation, the individuals that undergo genetic doubling get reproductively isolated from the original population because of incompatibility to mate even though they have close proximity with each other.

Therefore, the new species of evening primrose have arisen due to sympatric speciation.