Final answer:
The least important trait for a pioneering species is strong competition for resources. Good dispersal ability, fast reproduction, and tolerance of severe abiotic conditions are more important.
Step-by-step explanation:
In a pioneering species, the least important trait would be Strong competition for resources. Pioneering species are the first to colonize new habitats or areas with limited resources, so they typically face little competition initially. Instead, traits such as Good dispersal ability, Fast reproduction, and Tolerance of severe abiotic conditions are more important as they enable the species to establish and thrive in new environments.