Genomic variation among 42 strains of Crithidia bombi and C. expoeki

n this work, we have sequenced and analyzed 42 genomes of two Crithidia species, infecting bumblebees in Alaska and Central Europe and demonstrated that different strains of C. bombi and C. expoeki vary considerably in terms of single nucleotide polymorphism and gene copy number. Based on the genomic structure, phylogenetic analyses, and pattern of copy number variation, we confirmed the status of C. expoeki as a separate species. The Alaskan populations appear to be clearly separated from those of Central Europe. This pattern fits a scenario of rapid host-parasite co-evolution, where the selective advantage of a given parasite strain is only temporary. This study provides helpful insights into possible scenarios of selection and diversification of trypanosomatid parasites.