Molecular ecology of plant–microbial interactions during invasions: progress and challenges

Microbes are omnipresent, yet their interactions with invasive plants remain understudied. This is surprising, given the importance of microbes in plant community ecology and their influence on plant performance in new environments. Recent advances in molecular genetic approaches have opened the door to studying this unseen majority in great detail and to understand how they fit into ecological interaction networks. Molecular approaches allow rapid assessments of microbial diversity at reasonable cost while providing both taxonomic and evolutionary information. Here I discuss how these approaches have contributed to a better understanding of plant-microbial interactions in the context of biological invasions. By drawing insights from various case studies, I illustrate how next-generation sequencing (DNA barcoding) has revolutionized the way we understand such interactions. Tight-knit and coevolved mutualist (e.g. mycorrhizal) and antagonist (e.g. pathogen) interactions appear particularly promising to understand the structure and function of invasive plantmicrobial interaction networks, the impacts of invasive plants on native networks and the vulnerability of native networks to infiltration by non-native species. I also discuss novel ways in which molecular data can aid the study of invasive plant- microbial interactions, such as incorporating phylogenetic data into network analyses to better understand the role of evolutionary history in network dynamics and how such dynamics respond to plant invasions. DNA barcoding of microbes also presents unique challenges to the study of network ecology, such as uncertainty in the legitimacy and efficiency of interactions. Future research should incorporate overall plant-associated microbial communities (microbiomes) into interaction networks to better understand the role microbes play during plant invasions.