This research demonstrates that ambrosia fungi, which are cultivated by beetles as food sources, grow better on certain types of trees. The fungus studied, Dryadomyces montetyi, grows faster and denser on hardwood trees like oak and beech compared to conifer trees like fir and Douglas-fir. This suggests that the fungal symbiont has evolved preferences for the same tree types that its beetle partner prefers, indicating a specialized relationship shaped by millions of years of evolution.