Which statement about pioneer species is true?

• A. They appear late in succession
• B. They always prevent soil formation
• C. They are among the first to colonize bare substrate
• D. They require established soil

Answer: (C)

Pioneer species are the first organisms to colonize bare, nutrient-poor substrates and they start the process of soil formation. In primary succession, these hardy pioneers—things like lichens, mosses, and certain cyanobacteria—tolerate harsh conditions, physically and chemically break down rock, trap dust, and add organic material when they die. That initial soil buildup then allows other, more delicate species to establish, leading to a progression of communities over time.

So the statement that is true is that pioneer species are among the first to colonize bare substrate. The idea that they appear late in succession is incorrect, because they initiate succession. The notion that they always prevent soil formation is false; they actually promote it. The claim that they require established soil is also incorrect, since they establish where soil is not yet present and catalyze its formation.