New insights on the spore dispersal of Phallus indusiatus s.l. (Basidiomycota, Phallaceae) for the Brazilian Amazon forest

Spore dispersal by insects (entomochory) is a crucial relationship for phalloid fungi, as mycophagous insects carry large amounts of spores and assist stinkhorns in the colonization of new sites. Phallus indusiatus s.l. is a widely distributed fungal species (Basidiomycota), which recruits generalist mycophagous insects as dispersal agents for their spores. Given the lack of knowledge about the natural history of this relationship, it is assumed that its spores are mostly dispersed by insect feces. This study was conducted in a fragment of Amazon forest in Pará, Brazil, and we (i) identified the insects that visited P. indusiatus s.l., (ii) observed the behavior of the insects during this interaction, and (iii) counted the spores carried both on the body surface and in the stomach of the visiting insects. A total of 333 insects associated with six P. indusiatus s.l. basidiomes were recorded. Stingless bees devoted the most time to foraging and were the insects that carried the largest amount of spores, >83 million spores on the body surface and >60 million in the stomach. Wasps presented low abundance, with five minutes dedicated to foraging, carrying just over 7 million spores on the body surface and >2 million in the stomach. The beetles, although possibly sheltering in the basidiomes before the total maturation of P. indusiatus s.l., were the insects with less carried spores, 189,000 spores on the body surface and about 39,000 spores in the stomach. However, they were the most abundant insects among visitors, surpassing the 100 individuals in a single basidiome. Stinkhorns are very valuable resources for forest insects and these fungi take advantage of this interaction to disperse their spores via feces, but mainly by the body surface of visitors.