We present a discovery of a previously unknown ecological strategy in insect, which combines fungus farming and crop parasitism. Ambrosia beetles colonize dead trees, introduce symbiotic xylosaprophagous fungi into the trees using specialized organs (mycangia), and feed exclusively on these fungi. Exploitation of symbiotic fungi have allowed ambrosia beetles to utilize a wide variety of host trees, colonize nearly every habitat with woody vegetation, and become one of the most abundant guilds of beetles in tropical rainforests. The evolution of ambrosia symbiosis in previously phloeophagous weevils (bark beetles) occurred independently at least 11 times. We have recently discovered a previously unknown level of this foraging strategy in some ambrosia beetles for which we propose the term mycocleptism.

Results/Conclusions

A mycocleptic species seeks a gallery of its “provider species” – a regular ambrosia beetle species boring into a dead tree xylem and establishing a fungal garden. The mycocleptes then excavates its gallery adjacent to the provider species gallery. Thus mycelium originating in the provider’s gallery enters the mycocleptes’ gallery. The benefits of parasitism on a successfully established gallery include an abundance of fungal food, while avoiding the risk of the fungal transport failure, risk of fungal germination failure, and the risk of the symbiotic fungus death due to the competition by other inedible fungi. Mycocleptism appears to be largely a species-specific association. Four independent origins of mycocleptism have been discovered so far: Two species-rich clades of Xyleborina throughout the palaeotropics, one species of Platypodinae in New Guinea, and one species of Camptocerus (Scolytini) in Guyana. Phylogenetic and morphological analysis of a clade containing Biuncus gen. n., the largest mycocleptous group, revealed loss of fungus-transporting organs (mycangia) concurrent with the origin of mycocleptism. Extraction, cloning and comparison of DNA from fungi from many galleries of the beetle associates show that mycocleptous species always adopt fungal assemblages of the donor species.