American burying beetle genome and the response of burying beetles to pesticides

The American burying beetle (Nicrophorus americanus), a federally threatened species, has experienced significant population declines due to habitat loss, environmental changes, and potentially from pesticide exposure. Burying beetles exhibit unique behaviors including carcass burial, preservation, and biparental care. We sequenced the first whole genome assembly for a laboratory reared N. americanus from Oklahoma using PacBio HiFi technology and Hi-C sequencing. We had a total assembly length of 317Mpb and a BUSCO score of 99.7% of universal single-copy insect orthologs. We determined chromosome number and identified mitochondrial genes. This high-quality genomic resource enables a deeper understanding of the beetle’s population structure, demographic history, and genetic diversity. These genomic insights provide a foundation for conservation strategies, including population reintroduction and genetic rescue efforts. We also evaluated the effects of two widely used insecticides—imidacloprid (a neonicotinoid) and bifenthrin (a pyrethroid)—on burying beetles through direct exposure, soil-based bioassays, and reproductive tests. We found an LD₅₀ of 445.1 ng/beetle for imidacloprid and an LD₅₀ of 610.14 ng/beetle for bifenthrin from direct exposure. Although most tested Nicrophorus survived environmentally relevant exposure while in soils, behaviors were affected, and reproduction was reduced at 9 μg/kg soil treatment of imidacloprid. At high levels of bifenthrin no reproduction occurred. Although the number of larvae were reduced in other treatments, the size of larvae increased for 3 μg/kg imidacloprid treatments. Given the extensive agricultural use of these insecticides within the beetle’s remaining habitat, the findings underscore the need for pesticide management considerations in conservation planning. These studies provide essential genomic and ecological data to improve conservation for the American burying beetle.