Genome of Facultatively Parthenogenetic Harvester (Opiliones) Indicates Frequent Mitonuclear Sequence Transfer and Novel Full-Length Insertions

Facultative parthenogenesis and intrapopulation mixed ploidy (where individuals with differing ploidy exist within the same area) are rare in animals. However, these unique characteristics allow opportunities to investigate the relationship between sexual modality and genome structure. We have completed a genome assembly of the Japanese harvester ("daddy-longlegs") Leiobunum manubriatum, a species that reproduces sexually and asexually and has mixed diploid and tetraploid populations. We combined Oxford Nanopore's MinION long-read sequencing platform with Dovetail Hi-C scaffolding to assemble the haploid genome for the diploid race, which is approximately 336 Mbp after collapsing heterozygous sequence. The assembly's completeness was measured using BUSCOs from Arthropoda (complete: 97.7%). We also searched raw sequence reads and the draft genome for nuclear mitochondrial DNA (numt) sequences. While only one complete mitochondrial genomic transfer was found in the draft genome, there are at least 12 complete numts across nine reads within the raw sequencing data that were collapsed during the assembly process. The genome of the L. manubriatum diploid race is a valuable resource not only for opilionid research but also for facilitating studies investigating the evolution of their unique reproductive mode and mixed ploidy. To our knowledge, this is the first published genome of a wild-derived facultative parthenogen. Future work will leverage this resource in comparative genomics and transcriptomics of L. manubriatum to understand the connection between ploidy and sexual strategy.