Weevil species coexisting in a mixed oak forest show specificity among acorn species.
Acorn size differed among oak species and larval size differed among weevil species.
Acorn size drives the outcomes of the interaction for larvae and seedlings.
Acorn size constrains larval growth just in the larger weevil species.
Weevil specificity does not match the optimal predicted by acorn – weevil sizes.