Mutualism is a type of symbiotic relationship which involves the interaction of two different species of organisms interacting together to benefit from each other. In mutualistic relationship, both organisms involved depend on each other for nutrition, protection, reproduction or survival.
Mutualistic relationship can be seen between plant pollinators and flowering plants. The Monarch butterfly as a plant pollinator, depends on the milk-weed plant for nectar, while it helps the milk-weed plant in cross-pollination. Both organisms benefit from mutualism.
The fact that they can breed but cannot produce fertile offspring shows that they are different species. T<span>hey may have different characteristics which means they cannot breed </span>successfully, too.