Fungus‐animal symbioses have evolved countless times across the tree of life. While the stability of these mutualistic or parasitic interkingdom interactions often depends on optimised nutrient exchange, we lack a framework to explore whether animal‐derived nutrients are optimal for fungal symbionts. This conceptual gap has constrained studies about the ecological success and evolutionary stability of fungus‐animal symbioses....

Nutrition can mediate host–pathogen interactions indirectly when specific deficiencies (e.g., iron or glutamine) constrain host immune performance. Nutrition can also directly govern these interactions as invading pathogens colonize finite landscapes of nutritionally variable host tissues that must be optimally foraged during pathogen development. We first used a conceptual framework of nutritional niches to show that insect‐p...