With increased global travel and commerce, invasive species are a growing problem. This project investigates two invasive insects that infest, feed upon, and kill living trees. The emerald ash borer has killed hundreds of millions of North American ash trees since its introduction to the U.S. from East Asia two decades ago. It is expected to cause more than $10 billion in damage to the nursery and forestry industries as well as drastically change the composition of natural forests. Conversely, the red-turpentine beetle, native to North America, has become a major pest of pine forests in China since its introduction from the U.S. in the 1970s. Unfortunately, very little is understood about how these invasive beetles adapt to their new environments to become such destructive invasive pathogens. Microbes associated with beetles, either found living inside their guts or carried on the surface of the beetle from tree to tree, likely play an important role. Fungi and bacteria associated with other beetle species can degrade wood, cause tree disease, or produce volatile chemicals that attract even more beetles to an infested tree. In contrast, other microbes may be insect pathogens that produce toxins that could help control beetle populations. This research will employ both culturing and genome sequencing of microbes associated with these invasive beetles in both the U.S. and China in order to understand their biodiversity and how they may function to aid their insect hosts in becoming invasive species. The research also has potential to identify microbes that could be deployed for biological control of these forest pathogens. The project will share results with the public through exhibits at urban farmer’s markets, community workshops, and a public website. It will also train undergraduate and graduate students from underrepresented groups in STEM and build international collaboration through educational exchange and workshops.
Despite their importance in multi-trophic interactions, microbial symbionts of insects and the hidden roles they play in shaping biodiversity and maintaining the stability of forest ecosystems are often overlooked. This proposal will investigate the phylogenetic, functional, and genetic diversity of microbes associated with invasive wood-boring beetles to understand their role in facilitating invasion of their insect hosts. Aim 1 will use community analyses of phylogenetic diversity based on microbial culturing and metabarcode sequencing along with functional assays to uncover relationships between phylogenetic and functional diversity. The project will investigate specific metabolic functions of microbial communities that either contribute to the invasion process through degradation of lignocellulose in wood, detoxification of plant defense compounds, and production of metabolites that enhance beetle survival (e.g. vitamins and hormones) or that inhibit the invasion process (e.g. insect parasitism or synthesis of insect toxins). Aim 2 will use computational approaches to compare networks of taxa and/or gene functions in microbial communities from native and invasive ranges of each beetle to ask whether the evolution of novel symbiotic interactions between microbes leads to metabolic innovations that assist invasion. Aim 3 will use genome sequencing of fungal species associated with the invasive range to ask how microbial evolutionary genetic processes (e.g. horizontal gene transfer and genomic rearrangements) may alter the phenotypes of their insect hosts and drive the evolution of invasive symbioses. The project will elucidate how microbial symbionts of beetles help extend the functional phenotypes of their insect hosts.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
