Final answer:
The practice of intercropping, such as the 'Three Sisters' method or aquaculture intercropping in rice paddies with fish, serves as a mutualistic partner for both rice and wheat corn.
Step-by-step explanation:
The mutualistic partner for both rice and wheat corn is not a specific animal, but rather a practice known as intercropping. This is a technique in which different crops are planted together to mutually benefit each other. An example of this is the "Three Sisters" method, where corn, beans, and squash are grown in close proximity. Corn provides a structure for beans to climb, beans fix nitrogen in the soil which benefits the corn, and the broad leaves of squash help maintain soil moisture and suppress weeds. Rice farmers also introduce fish into their paddies, which is a form of aquaculture intercropping. The fish help to control pests and provide additional nutrients through their waste, while also being a protein source.