>>59052396>>59052485I did a little further digging into the topic and it's actually pretty complex. When two different colonies of fungus are introduced to each other in real life, they establish communication by smelling each other's chemical signals and tasting one another's cell proteins. If they're a matching species, they'll merge into a super colony, which is how we end up with ecological marvels like the mile-wide colony running below Central Park in New York. If the fungus colonies are of different species but share the same niche, they immediately start creating borders of thickened mycelium and chemically-enforced demarcation lines where no fungus can grow in order to deny area access, and then ramp up enzyme production in order to starve out their enemy until only one colony remains. If they don't have the same niche, they'll just ignore each other. Trychoderma is an outlier that actively predates other fungi by drilling into their mycelium cells and vampirising their nutrients.
Some species of fungus are known to trade nitrogen-rich compounds from deep underground with plant roots to nourish the plant in exchange for the plant releasing carbon-rich sugars to feed the mushroom; and likewise fungi and bacteria can work together to break down compounds that neither species could process on their own. Fungi could theoretically use these same channels to exchange nutrients between different species, but mushrooms are so poorly researched that we haven't proven this yet.
So the answer is: the mushroom Pokemon will ignore each other if they can get away with it, will avoid each other if possible, and then commit war crimes if they have to fight. Breloom will start throwing hands, Amoonguss will flood the air with poisonous spores to choke out their neighbors, Toedscruel and its little shadows will run for the hills, Parasect will try to eat its enemies' children and Shiinotic unleashes 11,000 lumens of fuck-you to cook the spores of their enemies.