Final answer:
The interaction between the American chestnut and Cryphonectria parasitica exemplifies parasitism and its significant impact on ecosystem dynamics, including changes in biodiversity and nutrient cycling.
Step-by-step explanation:
The interactions between the American chestnut and the parasitic fungus Cryphonectria parasitica best exemplify the ecological and evolutionary impact of a parasite on its host species and the broader ecosystem. When Cryphonectria parasitica, commonly known as the chestnut blight, was introduced to North America, it had a catastrophic effect on the American chestnut trees (Castanea dentata). This specific interaction illustrates the profound consequences of parasitism, which is a type of symbiotic relationship where one organism benefits at the expense of another.
The chestnut blight caused by Cryphonectria parasitica led to the near-elimination of the American chestnut from its native range, causing drastic changes in the forest ecosystems. These trees once played a critical role in forest structure, biodiversity, and nutrient cycling. The loss of the American chestnut also resulted in the extinction of several moth species that were host-specific, showcasing the ripple effect that the loss of a keystone species can have on ecosystem dynamics.