Our lab works at the interface of entomology and microbial ecology to uncover patterns of coevolution between insects and their microbiomes, and to better understand the role of the microbiome in insect biology. Our work is concentrated around both pests and beneficial insects that feed on lignocellulose, including beetles, cockroaches and termites.
Insects display a diversity of symbioses that is unmatched in the animal world, ranging from obligate intracellular endosymbiosis to intestinal microbiomes. While only some insect species possess these endosymbionts (e.g., Buchnera or Blattabacterium), all insect species are associated with complex communities of microbes in their guts, also called gut microbiomes.
Studies have shown that insects are colonized by host-specific microbiomes, and that the taxonomic composition reflects the evolutionary history of the hosts.
Our lab uses a combination of classical microbiology, molecular ecology, high-throughput sequencing, and entomology to study the coevolution of microbiomes with wood- and litter-feeding insects. These insects play essential roles in the turnover of lignocellulose in terrestrial ecosystems, but many species have gained notoriety as pests. Regardless, of whether they are beneficial insects or pests, several species have evolved to digest lignocellulose with the aid of their microbiomes.
Lignocellulose is the major structural component of plant cell walls, and is relatively recalcitrant to biochemical attack. So the few insect groups among the beetles and cockroaches that thrive on lignocellulose, have evolved symbiotic mechanisms to digest it.
Termites are exemplars of symbiotic digestion, especially of lignocellulose. They are essentially eusocial, morphologically reduced cockroaches, that evolved 150 million years ago from more primitive, and potentially detritivorous, cockroaches. Many termite species have diversified to feed on lignocellulose in different stages of decay, ranging from sound wood through litter, and humus. Their gut microbiomes are not only complex, but also unique in their composition; many of the bacterial and protozoan lineages found in these communities have only distant relatives in other environments.
Symbiotic digestion of lignocellulose involves the efficient breakdown of lignocellulose through a combination of mechanical and enzymatic action - the latter involves contributions from both the host and the microbiome. Despite the relative wealth of knowledge that exists about the mechanism of symbiotic digestion in termites, very little is known about how lignocellulose digestion may have evolved in other cockroach lineages or beetles.
One of the projects in the lab involves understanding the mechanism of symbiotic digestion of lignocellulose in insects feeding on dead wood and litter. We are primarily interested in identifying the symbionts involved in the digestion of different components of lignocellulose, and in the forces driving parallel evolution between these insects and their microbiomes.
The evolution of symbiotic digestion of lignocellulose has been crucial to not just the ecological dominance of termites, but also their infamous success as major structural pests. Termites are responsible for over $5 billion dollars in annual damage. Therefore, a mechanistic understanding of the termite-microbiome symbiosis could be critical to the development of ecologically sustainable methods of pest control.
A project in this direction is aimed at understanding the degree to which insect digestion, behavior, vigor, and fitness is influenced by its microbiome. We use a combination of native and invasive species of termites for our experiments involving targeted alterations to the gut microbiome; these include Reticulitermes spp., Zootermopsis spp., and Nasutitermes spp. However, because termites cannot be raised germ-free, they cannot be used for experiments requiring finer control of microbiome composition; for such experiments, we use our gnotobiotic cockroach model based on Shelfordella lateralis.