Red flour beetle (Coleoptera: Tenebrionidae) response to volatile cues varies with strain and behavioral assay

Authors: Gerken, Alison; Scully, Erin; Campbell, James - Jim

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2018
Publication Date: 10/3/2018
Citation: Gerken, A.R., Scully, E.D., Campbell, J.F. 2018. Red flour beetle (Coleoptera: Tenebrionidae) response to volatile cues varies with strain and behavioral assay. Environmental Entomology. 47(5):1252-1265. https://doi.org/10.1093/ee/nvy107.
DOI: https://doi.org/10.1093/ee/nvy107

Interpretive Summary: Stored product insects are major pests of facilities where grain is stored and/or processed, and monitoring using traps baited with pheromones and/or food is part of pest management programs. That insect attraction to pheromone and food odors can be influenced by environmental and physiological factors has been documented, but how different pest insect populations might vary genetically in their response to these cues is not well understood. In addition, different experimental methodologies have been used to measure insect response to pheromone and food odors, but different methodologies can be measuring different aspects of behavior and yield different results. Comparing response to pheromone and food odors using eight red flour beetle strains, collected from different locations around the world, and using three different behavioral assays revealed substantial variation in attraction to both food oil and pheromone, indicating that there are likely genetic differences that contribute to their ability to respond to these odors. The different behavioral assays differed in levels of air movement, distance to the pheromone/food, and whether they provided free exploration or were more constrained environments. We found that behavioral assay also plays a large role in responsiveness to these odors and contributes more to variation in behavior than genetic differences among strains. Overall, these results suggest that both genetics and environment can influence responsiveness to pheromone and food odors, and this information can help in the further evaluation of the genetic mechanisms of attraction and the methods used to evaluate attraction in stored product insects.

Technical Abstract: The red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae), is a major pest of facilities where grain is processed because of its ability to find and colonize food resource patches. Traps baited with pheromone and kairomone lures are commonly used to monitor presence of insects in warehouses or flour mills, for example. However, two non-mutually exclusive components, environment and genetics, could influence insect responsiveness to volatiles, impacting the efficacy of monitoring. Intra-specific variation in attraction behavior to food and mates is largely unexplored in stored product insects, but tapping into natural genetic variation could provide a baseline for identifying genetic mechanisms associated with finding resources. Here, we assess eight strains of T. castaneum for variation in response to kairomone- and pheromone-based lures using three behavioral assays: paired choice with no forced air flow, upwind attraction with forced air flow, and movement pattern in an arena with a single odor source. We find strain specific responses to kairomones and pheromones and evidence for heritability in behavioral responses. However, environmental coefficients for behavioral responses to both lures are high, suggesting that environment, and its potential interaction with genotype, strongly influences behavioral outcomes in these assays. Furthermore, despite the different environmental conditions among the different behavioral assays, we find a correlation for volatile preference among the three assays. Our results provide a baseline assessment of natural variation for preference to kairomone and pheromone lures and suggest that careful consideration of behavioral assay is key to understanding the mechanisms of attraction in these stored product pests.