Polyphagy on unpredictable resources does not exclude host specialization: insects feeding on mushrooms

Area of Science:

• Ecology
• Entomology
• Mycology

Background:

• Ecological specialization influences community structure but is difficult to compare across organisms.
• Environmental predictability is hypothesized to drive specialization, yet empirical support is limited.
• Fungi and their insect consumers offer a model system for studying host specialization.

Purpose of the Study:

• To test the predictability hypothesis by examining host specialization in fungus gnats (fungivores).
• To investigate the degree of host specialization in insects consuming mushrooms in North European boreal forests.
• To explore the multidimensional nature of ecological specialization in fungivore-fungus interactions.

Main Methods:

• Systematic sampling of mushrooms and rearing of fungivores from North European boreal forests.
• Application of parametric individual-based analyses to presence-absence data for estimating specialization.
• Classification of host use patterns at species, genus, family, and order levels.

Main Results:

• Contrary to expectations, most studied fungus gnats did not exploit host taxa indiscriminately.
• Some mushroom taxa remained uncolonized, and infestation rates varied among acceptable hosts.
• Host use was primarily explained by specialization at the genus level, with common fungivores showing preference for specific mushroom genera.

Conclusions:

• Fungus gnat host specialization is more nuanced than previously assumed, influenced by host unpredictability and chemical profiles.
• A high number of acceptable hosts does not negate significant discrimination among resource pools.
• Individual-based analyses are crucial for revealing fine-scale differences in ecological specialization and interaction intensities.