Chromosome-scale genome of a twig-girdler longhorn beetle reveals clustered genomic organization of herbivory-linked functions

<title>Abstract</title> <p> Herbivorous insects have diversified through repeated interactions with host plants. However, the genomic organization and transcriptional deployment that enables host use and tolerance of chemically defended tissues remain poorly characterized in many phytophagous lineages. We present a chromosome-scale genome assembly and multi-tissue, multi-stage transcriptomes for the Neotropical twig-girdler <italic>Oncideres impluviata</italic> (Germar) (Cerambycidae: Lamiinae). This pest species girdles living branches prior to oviposition and exploits at least 21 host species across five plant families. The assembly comprises 474.7 Mb (N50 = 39.4 Mb; BUSCO = 99.4%), with telomeric and synteny evidence supporting organization into 10 chromosomes, consistent with the conserved Lamiinae karyotype. Comparative analyses across phytophagous beetles reveal expansions in chemosensory (including a 40-gene Obp56d tandem cluster), neural signaling, detoxification, and digestive gene families, with Gene Ontology enrichment confirming bias toward host-interface functions. Across stages and tissues, host-interface expression concentrates in adults, with chemosensory genes in antennae and detoxification genes partitioned between antennae (odorant clearance) and thorax (systemic processing); sex bias is limited despite behavioral dimorphism. At the chromosomal level, 178 tandem clusters show significant overrepresentation of differentially expressed genes, and seven multi-family superloci co-localize clusters from different gene families, suggesting coordinated deployment of complementary host-interface functions. These results identify clustered genome architecture as a plausible substrate for rapid host evolution: tandem arrays and multi-family superloci concentrate standing variation in genomic regions where dosage and regulatory change can mediate host breadth, host shifts, and complex plant-manipulation behavior. The genome and transcriptome resources reported here support future comparative genomics in phytophagous beetles and management of twig-girdling pests. </p>