Final answer:
The gray squirrel acts as a competitor species in ecosystems, often leading to the decline of native species like the red squirrel due to its efficient foraging ability for nuts.
Step-by-step explanation:
The role the gray squirrel plays in the ecosystem can be described as a competitor species that influences the biodiversity within its environment. In Great Britain, for example, the introduction of the gray squirrel has led to a decline in native red squirrel populations due to resource competition. Gray squirrels are highly efficient at foraging for nuts, outcompeting red squirrels and causing a decrease in their numbers. This competition for resources shows how an invasive species can affect native species and the overall balance of an ecosystem.