Phylogenetic relationships of Isospora, Lankesterella, and Caryospora species (Apicomplexa: Eimeriidae) infecting lizards

In this study, several species of Isospora infecting lizards were genetically characterized. Specifically, five described and four newly described species of Isospora were included in a phylogeny of the family Eimeriidae. These species were isolated from hosts originally inhabiting all geographic continents except Europe. Phylogenetic analyses of the 18S ribosomal RNA (rRNA) gene grouped these nine species of Isospora with Lankesterella species and Caryospora ernsti. Therefore, within this clade, different evolutionary strategies in oocyst development and transmission occurred. Although the characteristic endogenous oocyst development of the genus Lankesterella may have arisen only once, the reduction in the number of sporocysts observed in the genus Caryospora occurred at least twice during coccidian evolution, as evidenced by the phylogenetic position of Caryospora bigenetica as the sister taxon of the group formed by reptilian Isospora, Lankesterella, and C. ernsti. Within this group, C. ernsti was the sister taxon to the genus Lankesterella. Overall, our results contradict the proposed monophyly of the genus Caryospora, highlighting the need for a thorough taxonomic and systematic revision of the group. Furthermore, they suggest that the recent ancestor of the genus Lankesterella may have been heteroxenous.