Fungal symbionts in three exotic ambrosia beetles, Xylosandrus amputatus, Xyleborinus andrewesi, and Dryoxylon onoharaense (Coleoptera: Curculionidae: Scolytinae: Xyleborini) in Florida

In nearly every forest habitat, ambrosia beetles (Coleoptera: Curculionidae: Scolytinae, Platypodinae) plant and maintain symbiotic fungus gardens inside dead or dying trees. Some non-native ambrosia beetles aggressively attack live trees and damage tree crops, lumber, and native woody plant taxa by introducing ambrosia fungi, some of which are plant pathogens. Most established exotic species, however, do not cause any economic damage, and consequently are little studied. To determine the specificity and diversity of ambrosia symbionts in under-studied non-native beetles in Florida, fungi were isolated from three species: Xylosandrus amputatus, Xyleborinus andrewesi, and Dryoxylon onoharaense. Two of the beetles sampled each yielded a fungal species isolated with 100 % frequency: X. amputatus: Ambrosiella beaveri or A. nakashimae, and X. andrewesi: Raffaelea sp. nov. nr. canadensis. Both of these symbionts have been isolated previously from closely related ambrosia beetles, supporting the hypothesis that some beetles can carry monocultures of fungi, but the fungi may not be specific to single beetle species. No consistent fungi were isolated from Dryoxylon onoharaense, raising questions about whether or not it truly carries its own symbionts. These results are now being used to test hypotheses and models explaining the evolution of pathogenicity within ambrosia fungi and invasion ability within exotic beetle-fungus complexes.