Advances in genomic studies of longhorn beetles (Coleoptera, Cerambycidae): a new reference genome and insights into the evolution and ecological diversity of twig-girdlers

Onciderini is one of the largest groups of flat-faced longhorn beetles in the Americas, with over 530 valid species. The onciderines are commonly referred to as twig-girdlers because the females of some species circumcise the branches of living plants for oviposition––a behavior that has economic effects on the forest industry. To understand the evolutionary aspects of twig-girdlers, we reconstructed the phylogeny of the tribe Onciderini and generated a reference genome for the twig-girdler, Oncideres impluviata (Germar), a major pest of black wattle trees (Acacia mearnsii De Wild) in southern of Brazil. Our phylogenetic inferences corroborate the monophyly of the tribe and recover all twig-girdler genera in a single clade. Using macro-evolutionary models, we demonstrate that behavior changes in Onciderini, from non-girdling to girdling, brought associated a number of morphological and ecological adaptations that influenced host plant range expansion in twig-girdlers, e.g., girdlers are sexually dimorphic (females have larger heads than males) and are able to use a much greater diversity of host plant families than non-girdlers.As for the reference genome of O. impluviata, we assembled 50.71x PacBio data from an adult male. The primary assembly, generated with Hifiasm, consisted of 153 contigs with N50 of 40.73 Mb and total assembly size of 493.13 Mb. Using the Insecta BUSCO gene set collection, 99.4% of the 1,367 genes were complete and 98.9% occurred as single copies. Our results shed light on important aspects of the evolution of longhorn beetles and provide new resources for comparative genomic studies of insects.