Multiple independent origins of apicomplexan-like parasites

Abstract

Apicomplexans are a diverse group of globally important parasites, that include pathogens like Plasmodium, the causative agent of malaria. Despite their current obligate parasitic nature, apicomplexans evolved from photosynthetic algae and retain a remnant plastid (chloroplast). Such a complex evolutionary transition was unexpected, but here we show that it occurred at least three times independently. Using single-cell genomics and transcriptomics from diverse uncultivated parasites, we find that two genera previously classified within the Apicomplexa, Piridium and Platyproteum, form separately branching lineages in phylogenomic analyses. Both retain cryptic plastids with genomic and metabolic features convergent with apicomplexans. These findings suggest a predilection in this lineage for both the loss of photosynthesis and the transition to a morphologically similar parasitic lifestyle, resulting in multiple lineages of highly convergent animal parasites.