Invasive ambrosia beetles, fungal symbiont infidelity, and a bleak future for naïve tree species

Invasive ambrosia beetles (23 spp. in the US in 2010) are emerging as a new and currently uncontrollable threat to forest health and fruit industry throughout the US. In this project we will test whether fungal symbionts of exotic ambrosia beetles play a role in successful invasions and establishment. Our approach combines global sampling with next-generation sequencing of mycangial fungal communities, and will allow us to address four major unkowns of the ambrosia symbiosis: a. Is the beetle-fungus association highly specific, or is there a rich and variable community of fungi in beetle mycangia? b. Does the community vary across localities, tree hosts or climatic conditions? c. Is there any evidence of fungus-switching, especially between native and invasive beetles? d. Are invasive beetles associated with the same symbionts in their native region as in the invaded region? We are exhaustively analyzing communities of fungal symbionts in 20 spp. of both native and exotic ambrosia beetles by culturing techniques, and 12 spp. of beetles by 454 deep sequencing (PCR-amplified LSU rDNA community library directly from mycangia, sequenced on GS FLX Titanium, 454 Life Sciences). Current status: 1) Developed reliable methods for excision of all three types mycangia in Xyleborini (mandibular, mesothoracic, and pronotal). 2) Isolated 93 ambrosia fungal and yeast isolates from 11 beetle species (63 individuals). 3) Extracted DNA of complete mycangial community from mycangia of 8 beetle species (35 individuals). 4) 454 multiplex primers for LSU rDNA were developed that preferentially amplify fungal DNA over beetle DNA. Further analyses are in progress at the time of paper submission.