With the exception of flagellated spores for members of the Chytridiomycota, fungi are mostly nonmotile. What adaptive feature allows them to be such successful decomposers, pathogens, and symbionts even though they lack motile cells?

The reproduction via means of spores which can be easily dispersed

Explanation:

Spores are the reproductive structures produced by the lower organism. The spores produced provide many benefits to the organisms like fungi as they can be dispersed to a longer distance therefore spores acts as an adaptive mechanism of the organism for dispersal.

During the favourable condition, the spores germinate to produce a mature organism. This ability has allowed the fungi to grow in many conditions in a different type of substratum where they interact and can become pathogenic, can become symbionts or decomposers.

Thus, the reproduction via spores is correct.