A reference genome for Trichogramma kaykai: a tiny desert-dwelling parasitoid wasp with competing sex-ratio distorters.

The tiny parasitoid wasp Trichogramma kaykai inhabits the Mojave Desert of the southwest United States. Populations of this tiny insect variably host up to 2 different sex-distorting genetic elements: (1) the endosymbiotic bacterium Wolbachia which induces the parthenogenetic reproduction of females, and (2) a B-chromosome, "Paternal Sex Ratio" (PSR), which converts would-be female offspring to PSR-transmitting males. We report here the genome of a Wolbachia-infected T. kaykai isofemale colony KSX58. Using Oxford Nanopore sequencing, we produced a final genome assembly of 205 Mbp with 34× coverage, consisting of 154 contigs with an N50 of 2.2 Mbp. The assembly is quite complete, with 92.67% complete Hymenoptera BUSCOs recovered: a very high score for Trichogrammatids that have been previously characterized for having high levels of core gene losses. We also report a complete mitochondrial genome for T. kaykai, and an assembly of the associated Wolbachia, strain wTkk. Finally, we identified copies of the parthenogenesis-inducing (PI) genes pifA and pifB in a remnant prophage region of the wTkk genome and compared their evolution to pifs from a suite of other PI Wolbachia. The T. kaykai assembly is one of the highest quality genome assemblies for the genus to date and will serve as a great resource for understanding the evolution of sex and selfish genetic elements.