Gut bacterial symbiont diversity within beneficial insects linked to reductions in local biodiversity

Authors: Schmid, Ryan; Lehman, R - Michael; VOLKER, BROZEL - South Dakota State University; Lundgren, Jonathan

Submitted to: Annals of the Entomological Society of America
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2015
Publication Date: 12/7/2015
Citation: Schmid, R.B., Lehman, R.M., Volker, B., Lundgren, J.G. 2015. Gut bacterial symbiont diversity within beneficial insects linked to reductions in local biodiversity. Annals of the Entomological Society of America. 108(6):993-999, doi: 10.1093/aesa/sav081.

Interpretive Summary: Bacterial symbionts within insect guts can provide valuable benefits to insects and land managers; their symbionts also help to define where these insects fit within food webs. We tested whether factors that encourage biodiversity within a habitat are linked with the bacterial diversity found within cricket stomachs. The plant and insect diversity was measured in prairies, pastures, and cornfields of Brookings, County, SD (n = 3 per habitat). Two species of crickets were collected from each of these fields, and the number of bacterial species in each cricket gut was enumerated using genetic techniques (tRFLP analysis). We found that cornfields had approximately 25% of the biodiversity found in more stable, complex habitats. Bacterial species in cricket stomachs followed a similar pattern, and were predictable based on the species richness found in a particular habitat. Bacterial symbionts per cricket were strongly reduced in cornfields. Thus agriculture not only diminishes biodiversity within a habitat, but also potentially limits symbiont-driven benefits that the remaining species can provide.

Technical Abstract: Understanding the factors that constrain or promote symbiotic microbial communities gives a clearer picture of the niches that can be occupied by a host organism. Many insects harbor symbiotic microbes that can alter various aspects of insect behavior and biology including diet digestion, sex determination, and pathogen defense. Habitat diversity has a major influence on insect and microbial diversity within an environment. In the current study we assessed how habitat biodiversity affects the bacterial species richness within the gastrointestinal tract of insects. We measured species abundance of plants and insects present in three replicated habitats (prairie, pasture, and maize fields) that inherently represent a continuum of biological diversities. Gut bacterial symbiont diversity of the crickets Gryllus pennsylvanicus and Allonemobius sp. were described using terminal restriction fragment length polymorphism analysis of rRNA genes. The resulting data show that gut bacterial diversity of both cricket species is positively correlated with habitat biodiversity. This demonstrates that microbial diversity within insect stomachs, and presumably their functions within these insects, is tied to the biodiversity within the habitats where insects live. These results have important implications as to how reductions in habitat biodiversity affects the ecological functions and services that the remaining species can perform.