Comparative genomic analysis of necrophagous and parasitic subspecies of Lucilia cuprina (Diptera: Calliphoridae) provides important insight into their divergent biologies.

Lucilia cuprina, a species of blowfly, consists of two recognized subspecies: L. cuprina cuprina and L. cuprina dorsalis. Although they are morphologically and molecularly similar to each other, they have very different ecological roles. In Australia, L. c. dorsalis is predominantly found in rural areas and is the primary causative agent of sheep myiasis (flystrike), while L. c. cuprina is necrophagous and not a significant pest of livestock in the Americas or elsewhere. Here, we present a chromosome-scale genome assembly for L. c. cuprina and an improved assembly for L. c. dorsalis, enabling comparative genomic analysis between these subspecies. While both genomes share a similar gene content, subspecies-specific genes were identified, which may contribute to their divergent ecological roles -necrophagy in L. c. cuprina and parasitism in L. c. dorsalis. Phylogenetic analyses across target genomic regions reaffirm the close relationship between L. c. cuprina and L. c. dorsalis and position L. sericata as their sister species. Gene mutations linked to diazinon resistance were exclusively observed in L. c. dorsalis, whereas malathion resistance was detected in both subspecies. Additionally, we identified genes with accelerated evolutionary rates in each subspecies, which may underlie their distinct feeding behaviours. We also conducted a detailed analysis of chemosensory genes, revealing that L. c. dorsalis possesses slightly larger repertoires of all four chemosensory gene families studied. In comparison to Drosophila melanogaster, both subspecies exhibit an expanded gustatory receptor clade. Our findings provide valuable insights into the genetic factors underpinning parasitism and insecticide resistance and provide a valuable genetic resource for future research endeavours, including the development of engineered strains aimed at genetic biocontrol strategies. This work enhances our understanding of the evolutionary adaptations for this important blowfly species.