Answer:
A. Competition has restricted the ranges of both species.
Step-by-step explanation:
The most likely cause of the realized niches of the two wildflower populations to be smaller than their fundamental niches is competition.
The fundamental niche of an organism represents the entire resources and area an organism has given that there are no limiting factors within the environment.
The realized niche of an organism represents the resources available and the area an organism has due to limiting factors within the environment, especially competition for resources and spaces.
The realized niche results from competition for resources within the fundamental niche. Hence, they are usually smaller than the fundamental niche of an organism.
The correct option is A.