In this question, notice that the conclusion of the argument, "the presence of dandelions facilitates pollination (and hence seed production) in the native species by attracting more pollinators to the mixed plots," is supported by the information that, in a recent study, researchers selected 16 plots containing both species; all dandelions were removed from eight plots; the remaining eight control plots were left undisturbed, and the control plots yielded significantly more larkspur seeds than the dandelion-free plots.

The conclusion seem logical, but does it really follow from the evidence? What would cast doubt on the idea that the conclusion follows from the evidence?