Chromosome-level genome assemblies of Osmia cornifrons and Osmia taurus (Hymenoptera: Megachilidae), two introduced species in North America

The mason bees Osmia cornifrons and Osmia taurus (Hymenoptera: Megachilidae) are native to eastern Asia. While O. cornifrons was intentionally introduced in the United States for orchard pollination more than 40 years ago, its congener O. taurus, was accidentally and recently introduced. Both species are now widespread across eastern North America, while native Osmia species are declining. The mechanisms by which the introduced species have been able to establish and spread are currently unknown. Here, we present high-quality genome assemblies of O. cornifrons and O. taurus that will serve as a resource to study the genomic basis of their successful establishment in North America. We combined PacBio HiFi long-read sequencing, Hi-C short-read sequencing, and RNA data to assemble and annotate the genomes. The genomes of O. cornifrons and O. taurus represent some of the largest genomes sequenced in Megachilidae, with more than half of their genomes composed of repetitive elements. Despite challenges with Hi-C scaffolding due to the high repeat content, we assembled most of the genomes into 16 chromosomes. Genome annotation recovered protein-coding gene counts similar to other Osmia reference genomes, while repetitive element annotation indicated that at least 60% of the repeats are novel. This result might be due to biases in the repeat databases, highlighting the challenges of non-model organism annotation. The genomes presented here will serve as references for invasion genomics projects that will elucidate the success of O. cornifrons and O. taurus, as well as their potential detrimental effects on the native bee fauna.