Insect-mediated spore dispersal in calicioid fungi: an experimental approach

Many calicioid fungi accumulate ascospores into an adhesive mass, called the mazaedium, at tips of stipitate apothecia. Fossil specimens from European ambers demonstrate that this morphology had evolved by the Paleogene and has since remained unchanged. The conserved maintenance of a spore-saving strategy is probably linked to animal-vectored dispersal, but experimental evidence confirming this is lacking. Here, we approached the question with a series of experiments, in which ascomata of three distantly related calicioid species were exposed to living individuals of four insect species. The results confirmed that calicioid ascospores are readily attached to any insects that touch the mazaedial spore mass. Adhered ascospores could be recovered from insect surfaces with ultrasonic cleaning. We found no significant differences in the amounts of attached ascospores of different fungal species. We discuss the new findings in the context of previous observations supporting the ecological and evolutionary role of animal-vectored dispersal in calicioid fungi.