Bacterial Endosymbionts That Facilitate Granivory in Omnivorous Insects
North Central Agricultural Research Laboratory
2013 Annual Report
1a.Objectives (from AD-416):
Investigate the contributions of symbiotic gut bacteria to the feeding ecology of carabid beetles and crickets. Specifically, substantiate which bacteria facilitate granivory of weed seeds by these insects and how environmental, phylogenetic, and physiological factors constrain these relationships.
1b.Approach (from AD-416):
Feeding assays and insect collections from cropland will be used to identify the effects of specific bacterial constituents of the community that contribute to seed digestion. Bacterial culture methods will be combined with PCR-based methods to identify and isolate bacterial communities from carabid and cricket guts from cropland in our region. Experimental endpoints that will be assessed include seed consumption rates and the relative digestibility of seeds by the insects.
Experiments involving the effects of bacterial symbionts (Enterococcus faecalis) on seed consumption by carabid beetles were completed, and the manuscript submitted to a peer-reviewed journal. Experiments investigating how antibiotics affect cricket food preferences (for prey or seeds) were completed. DNA analysis of the cricket guts to substantiate that microbial communities were reduced or eliminated using antibiotics are underway, and the manuscript is in preparation. A field study was initiated in 2012 to determine how habitat diversity (grass, arthropod diversity) affects the diversity of gut symbionts in crickets. Habitat diversity of nine experimental sites were described, more than 300 taxa were distinguished across these different habitats. Two species of crickets were collected, and their guts were analyzed for microbial diversity. Preliminary analysis suggests that microbial diversity scales with diversity within a habitat. Thus conservation programs that increase diversity in an agroecosystem are likely to provide more symbiotic microbe-insect interactions and the services that these symbioses support.