The UF Forest Entomology Lab is embarking on a new set of experiments to better understand a recent pair of invaders that could potentially have an outsized impact on the environment. The ambrosia beetle Ambrosiodmus minor and its fungal symbiont Flavodon ambrosius are a pair of introduced species from Southeast Asia which are unusual because unlike most beetle-borne fungi, F. ambrosius is a wood-decaying fungus.
Among approximately 3,000 species of ambrosia beetles, which transport and cultivate specific fungi that serve as their sole source of food, only five are currently known to carry fungi that decay wood (though it is likely that there are more to be identified). Flavodon‘s ability to decay wood could have a broader effect in its introduced environment, impacting the forest microbiome.
“Flavodon offers an example of how [introduced beetles] might be kind of quietly changing ecosystem dynamics,” says Dr. James Skelton, part of the team researching the invasion, “introducing a fungus that is breaking down wood, getting there faster than other decay fungi, perhaps competing with native fungi and excluding native biodiversity.”
“Flavodon seems to out-compete other decay fungi,” says Demian Gomez, a PhD candidate leading the new study. “This fungus can grow really fast and outpace the other decay fungi.”
The first specimens of A. minor and Flavodon in North America were found in Jacksonville, Florida in 2011. Since then, the symbionts and their hosts have spread rapidly and become one of the most common species of ambrosia beetles in Northern Florida. They have also been collected in Georgia, Alabama and Mississippi. Analysis of their native range in Asia suggests that the beetles and fungi will probably be able to tolerate cold weather well enough to continue moving north into the forests of the mid-Atlantic.
A. minor can colonize many species of tree and is not specific to any particular clade of host plants. Even pine trees, with their unique set of chemical defenses, can be colonized. However, the beetles have not yet been observed attacking healthy trees. They target dead and dying hosts.
The experiment beginning this month involves inoculating 21 wooden logs with Flavodon. A control group of 21 identical logs were not inoculated. Innoculation was accomplished by drilling out a dozen holes in each log and filling them with wooden pegs pre-colonized in the lab with Flavodon. The control group received sterilized wooden pegs. The logs will be left in a forest for approximately seven months and then sampled to determine the composition of their respective fungal communities.
“We’ve seen that Flavodon is pretty aggressive,” Gomez says. “We’re going to test how it actually effects the natural communities of fungus. We want to quantify exactly how aggressive it is competing against other species in the fungal community.”
“These beetles are very abundant, they’re infesting a lot of trees and they are bringing in a novel fungus that is capable of doing pretty extensive decay,” says Skelton. “And that entry into the wood that Flavodon has is pretty unique among decay fungus. Most of them have to get in through wind blown spores, or wait for a limb to break… but having a beetle to fly you around and bore a hole through the bark and innoculate that fungus into freshly dead wood is an advantage that pretty much no other decay fungus has.”
“We might see increased decomposition rates and consequently more carbon released as CO2 as the wood decomposes,” Skelton says.