Chromosome-scale genomes of the flightless caterpillar hunter beetles Calosoma tepidum and Calosoma wilkesii from British Columbia (Coleoptera: Carabidae).

Abstract

The giant ground beetle genus Calosoma (Coleoptera, Carabidae) comprises ca. 120 species distributed worldwide. About half of the species in this genus are flightless due to a process of wing reduction likely resulting from the colonization of remote habitats such as oceanic islands, highlands and deserts. This clade is emerging as a new model to study the genomic basis of wing evolution in insects. In this framework, we present the de novo assemblies and annotations of two Calosoma species genomes from British Columbia, Calosoma tepidum and Calosoma wilkesii. Combining PacBio HiFi and Hi-C sequencing, we produce high-quality reference genomes for these two species. Our annotation using long-read RNAseq and existing Coleoptera protein evidence, identified a total of 21,976 genes for C. tepidum and 26,814 genes for C. wilkesii. Using synteny analyses, we provide an in-depth comparison of genomic architectures in these two species. We infer an overall pattern of chromosome-scale conservation between the two species, with only minor rearrangements within chromosomes. These new reference genomes represent a major step forward in the study of this group, providing high-quality references that open the door to different approaches such as comparative genomics or population scale resequencing to study the implications of flight evolution.