Oyen, K. J. | bioRxiv Science

bioRxiv2025

Sub-lethal pesticide exposure facilitates the potential northward range shifts of ticks by increasing cold tolerance and overwintering survival

Pesticides are a primary tool for the control of harmful insects or other organisms throughout the world. Although most organisms are likely to encounter pesticides in the environment, little is known about the effects of these chemicals on the physiology of off-target species. We measured the impact of sublethal pesticide exposure on the cold tolerance of two common tick species. We predicted that sublethal pesticide exposure would make ticks more sensitive to extreme temperatures. In contrast, we found that exposure to sublethal pesticides had the opposite effect, increasing survival at low temperatures. Sublethal pesticide exposure decreased the LT50 (lethal temperature at which 50% mortality is observed) of adult and nymphal D. variabilis from -16{degrees}C to -19{degrees}C and improved overwintering survival. Evaluation of previously available RNA-seq data between rapid cold hardening and pesticide exposure indicated potential transcriptional shifts associated with cross-tolerance between cold and pesticide exposure. To investigate the population-level impacts of this physiological shift in cold tolerance, we developed a novel approach for incorporating physiological survival data into spatially explicit species distribution models (SDMs). Using this approach, we demonstrate that pesticide-induced increases in cold tolerance may permit faster northward range shifts of D. variabilis. We also demonstrate that incorporating physiological data into SDMs moderates the estimated impacts of environmental change and may provide more accurate predictions of species responses to changing environments. Although our study is limited to ticks, other studies have shown the effects of pesticides on thermal tolerance traits in diverse species. The extensive use of pesticides may drive complex interactions between species and their environments, leading to altered thermal tolerance traits and establishment in new habitats.

ecology↗

bioRxiv2019

Functional genomics of the stable fly, Stomoxys calcitrans, reveals mechanisms underlying reproduction, host interactions, and novel targets for pest control

BackgroundThe stable fly, Stomoxys calcitrans, is a major blood-feeding pest of livestock that has near worldwide distribution, causing an annual cost of over $2 billion for control and product loss in the United States alone. Control of these flies has been limited to increased sanitary management practices and insecticide application for suppressing larval stages. Few genetic and molecular resources are available to help in developing novel methods for controlling stable flies.\n\nResultsThis study examines stable fly biology by utilizing a combination of high-quality genome sequencing, microbiome analyses, and RNA-seq analyses targeting multiple developmental stages and tissues. In conjunction, manual curation of over 1600 genes was used to examine gene content related to stable fly reproduction, interactions with their host, host-microbe dynamics, and putative routes for control. Most notable was establishment of reproduction-associated genes and identification of expanded vision, chemosensation, immune repertoire, and metabolic detoxification pathway gene families.\n\nConclusionsThe combined sequencing, assembly, and curation of the male stable fly genome followed by RNA-seq and downstream analyses provide insights necessary to understand the biology of this important pest. These resources and knowledge will provide the groundwork for expanding the tools available to control stable fly infestations. The close relationship of Stomoxys to other blood-feeding (Glossina) and non-blood-feeding flies (medflies, Drosophila, house flies) will allow for understanding the evolution of blood feeding among Cyclorrhapha flies.

genomics↗