We study animal-microbe interactions. We’re particularly interested in how these associations evolve and the underlying molecular and immunological mechanisms. We rely on experimental, genetic, and genomic techniques, and we currently work on an insect model system: the pea aphid and its well-characterized community of bacterial and fungal partners.


Vertically-transmitted microbes & host evolution:

Several species of bacteria live inside of aphids and are transmitted from mothers to offspring. The patterns of symbiont infection across aphid populations are non-random, and we’ve found that some of this variation can be explained by genetic differences among aphid lines. We are harnessing this natural host genetic variation to understand:

  • How host mechanisms influence symbiont community structure and function and how these mechanisms are evolving

  • How host immune systems manage their dual role of combatting harmful infections while fostering beneficial microbes


Protective symbionts and host-pathogen coevolution:

Animal-associated microbes often have specific phenotypic effects on their hosts—for example Regiella insecticola makes aphids resistant against an important natural enemy, the fungal pathogen Pandora neoaphidis. We are studying this three-way coevolutionary interaction to learn:

  • Why and how protective microbes help their hosts and what keeps beneficial microbes from cheating

  • How symbiotic partners achieve specificity within and among species and what these patterns teach us about host-microbe coevolution

Lateral transfer of microbial genes and animal phenotypes:

Vertically-transmitted viruses are often hidden players affecting host phenotypes. A number of these viruses have been described in aphids, and viral genes have been frequently incorporated into aphid genomes. We’ve found that viral genes with homology to Dysaphis plantaginea Densovirus are expressed by pea aphids and play a role in the phenotypically plastic production of winged offspring by aphids in response to environmental cues. We’re using this system to study how vertically-transmitted viruses are regulated by hosts, how viral genes influence host gene expression, and how these genes are then regulated when they become incorporated into host genomes.