Phylogenomics from transcriptomic "bycatch" clarify the origins and diversity of avian trypanosomes in North America

The eukaryotic blood parasite genusTrypanosomaincludes several important pathogens of humans and livestock, but has been understudied in wildlife broadly. The trypanosomes that infect birds are in particular need of increased attention, as these parasites are abundant and globally distributed, yet few studies have addressed their evolutionary origins and diversity using modern molecular and analytical approaches. Of specific interest are the deep evolutionary relationships of the avian trypanosomes relative to the trypanosome species that are pathogenic in humans, as well as their species level diversity in regions where they have been understudied such as North America. Here, we address these unresolved areas of study using phylogenomic data for two species of avian trypanosomes that were isolated as "bycatch" from host transcriptome assemblies, as well as a large 18S DNA barcode sequence dataset that includes 143 novel avianTrypanosoma18S sequences from North America. Using a phylogenomic approach, we find that the avian trypanosomes are nested within a clade of primarily mammalian trypanosomes that includes the human pathogenTrypanosoma cruzi, and are paraphyletic with respect to the ruminant trypanosomeTrypanosoma theileri. DNA barcode sequences showed thatT.aviumand an unidentified small, non-striated trypanosome that was morphologically similar toT.everettiare each represented by highly abundant and divergent 18S haplotypes in North America. Community-level sampling revealed that additional species-levelTrypanosomalineages exist in this region. We compared the newly sequenced DNA barcodes from North America to a global database, and found that avianTrypanosoma18S haplotypes generally exhibited a marked lack of host specificity with at least oneT.aviumhaplotype having an intercontinental distribution. This highly abundantT.aviumhaplotype appears to have a remarkably high dispersal ability and cosmopolitan capacity to evade avian host immune defenses, which warrant further study.