Mycorrhizal fungi are sometimes purposely introduced to new areas of land that are used for growing plants for commercial uses (e. g., landscaping, crop production, timber production). what would be the benefit of doing this?

The fungi help facilitate horticulture, agriculture and forestry.

Explanation:

A mycorrhizal association is a symbiotic mutualistic association between the land plants and the fungi. The fungus colonizes over the host plant roots and supplies mineral nutrients from the soil in return the plant receive sugars by the process of photosynthesis.

Thus the fungi will help in healthy growth of plants. Hence, facilitate in horticulture, agriculture and forestry.

not necessarily. higher fitness requires the organism to be reproductive successful. for example, an organism at age 10 with 15 offspring is much more fit than an organism at age 15 with only 5 offspring.