Hoverflies use a time-compensated sun compass to orientate during autumn migration

This is the final version. Available on open access from the Royal Society via the DOI in this recordData accessibility: All data are provided as electronic supplementary material [59].The sun is the most reliable celestial cue for orientation available to daytime migrants. It is widely assumed that diurnal migratory insects use a ‘time-compensated sun compass’ to adjust for the changing position of the sun throughout the day, as demonstrated in some butterfly species. The mechanisms used by other groups of diurnal insect migrants remain to be elucidated. Migratory species of hoverflies (Diptera: Syrphidae) are one of the most abundant and beneficial groups of diurnal migrants, providing multiple ecosystem services and undergoing directed seasonal movements throughout much of the temperate zone. To identify the hoverfly navigational strategy, a flight simulator was used to measure orientation responses of the hoverflies Scaeva pyrastri and Scaeva selenitica to celestial cues during their autumn migration. Hoverflies oriented southwards when they could see the sun and shifted this orientation westward following a 6 h advance of their circadian clocks. Our results demonstrate the use of a time-compensated sun compass as the primary navigational mechanism, consistent with field observations that hoverfly migration occurs predominately under clear and sunny conditions.Royal SocietyNatural Environment Research Council (NERC)European Union Horizon 2020American Airforce Research Laboratory (AFRL)Bristol Centre for Agricultural Innovation (BCAI

Genome-wide transcriptomic changes reveal the genetic pathways involved in insect migration

This is the final version. Available on open access from Wiley via the DOI in this recordData availability statement: The datasets and metadata supporting the results of this article have been deposited at DDBJ/ENA/GenBank and are available via Bioproject PRJNA720810. The genome assembly described in this paper has been deposited under the accession JAGTYB000000000. The version described in this paper is version JAGTYB010000000. Tissue level RNAseq data is available from the Gene Expression Omnibus (GEO) repository via GSE205498. Genome and repeat annotation files are available on figshare 10.6084/m9.figshare.19333181.Insects are capable of extraordinary feats of long-distance movement that have profound impacts on the function of terrestrial ecosystems. The ability to undertake these movements arose multiple times through the evolution of a suite of traits that make up the migratory syndrome, however the underlying genetic pathways involved remain poorly understood. Migratory hoverflies (Diptera: Syrphidae) are an emerging model group for studies of migration. They undertake seasonal movements in huge numbers across large parts of the globe and are important pollinators, biological control agents and decomposers. Here, we assembled a high-quality draft genome of the marmalade hoverfly (Episyrphus balteatus). We leveraged this genomic resource to undertake a genome-wide transcriptomic comparison of actively migrating Episyrphus, captured from a high mountain pass as they flew south to overwinter, with the transcriptomes of summer forms which were non-migratory. We identified 1543 genes with very strong evidence for differential expression. Interrogation of this gene set reveals a remarkable range of roles in metabolism, muscle structure and function, hormonal regulation, immunity, stress resistance, flight and feeding behaviour, longevity, reproductive diapause and sensory perception. These features of the migrant phenotype have arisen by the integration and modification of pathways such as insulin signalling for diapause and longevity, JAK/SAT for immunity, and those leading to octopamine production and fuelling to boost flight capabilities. Our results provide a powerful genomic resource for future research, and paint a comprehensive picture of global expression changes in an actively migrating insect, identifying key genomic components involved in this important life-history strategy.Royal SocietyNatural Environment Research Council (NERC)Biotechnology and Biological Sciences Research Council (BBSRC