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Skelton J, Loyd A, Smith JA, Blanchette RA, Held BW, Hulcr J.2019. Experimental evidence that fungal symbionts of beetles suppress wood decay by competing with decay fungi. PeerJ Preprints7:e27676v1https://doi.org/10.7287/peerj.preprints.27676v1
Throughout forests worldwide,bark and ambrosia beetles inoculate dead and dying trees with symbiotic fungi. We experimentally determined the effects of three common and widely distributed ascomycete symbionts, and one introduced Asian basidiomycete symbionton the decay of pine sapwood. Ascomycetes caused less than 5% mass loss and no structural degradation, whereas the basidiomycete Flavodon ambrosius caused nearly 15% mass loss and visible degradation of wood structure. In co-inoculation experiments, the beetle symbionts Ophiostoma ips and Raffaelea fusca reduced white and brown rot decay through competition with Ganoderma curtisii and Phaeolus schweinitzii, respectively.The inhibitory effects of O. ips and R. fusca on decay were negated when co-inoculated with F. ambrosius, suggesting that widespread introduction of this beetle symbiont could alter forest carbon fluxes. In contrast to the predominant forest biology narrative, most bark and ambrosia beetles introduce fungi that delay rather than facilitate tree biomass recycling.
This manuscript provides first experimental evidence that the symbiotic fungi of bark and ambrosia beetles reduce decay rates of pine sapwood by competing with wood decay fungi. This is the first version and will soon be submitted to a peer-reviewed journal.