She the stranger, the foreigner, of alien blood and mind, did not share his power or his conscience or his knowledge or his exile. She shared nothing at all with him, but had met him and joined with him wholly and immediately across the gulf of their great difference: as if it were that difference, the alienness between them, that let them meet, and that in joining them together, freed them.
—Ursula Le Guin. Planet of Exile.
New species of plants and fungi can alter the interactions of native species. Here the native hyperparasite of ergots, Fusarium heterosporum, has formed a new relationship with the ergot Claviceps spartinae and its grass host Sporobolus (Spartina) anglicus, both of which have been introduced to Ireland in the last 120 years.