Correlating latitudinal origin with variation in diapause-associated genes in the blue orchard bee Osmia lignaria

The blue orchard bee (Osmia lignaria) is a native solitary species commonly used in agricultural pollination in the USA. Osmia lignaria employ an obligate overwintering strategy by entering diapause to survive winters, with variation in timing and duration across populations in different latitudinal regions. Diapause timing is critical for commercially managed species where farmers require bee emergence to match the flowering of crops. As diapause timing is known to have a genetic basis in this species, we investigated how genomic variation contributes to the overwintering phenotype in O. lignaria. We sequenced genomes from five populations of O. lignaria across a latitudinal gradient to identify differences and similarities in genes related to diapause across populations. Candidate genes include insulin-signaling genes, heat-shock proteins involved in temperature cues, and genes related to immune system function, stress response, and fatty acid and lipid metabolism. Variation in these genes will also be compared across species with different overwintering behavior, such as those with facultative diapause or hybrid strategies. Following geographic trends of emergence, we expect to find differences in candidate genes as a function of latitude. Comparisons across species will additionally assist understanding of the core genes regulating diapause.