ИСТИНА

Nucleotide sequences of rDNAs (SSU, 5.8S, LSU) of plesiomorphic parasitic Apicomplexa including Archigregarinida, Blastogregarinea, Protococcidia were studied. Unlike traditional view (just two main lineages: gregarines and coccidians), the obtained phylogenetic trees demonstrate several lineages with unresolved backbone: eucoccidians+hematozoans, Rhytidocystis+Coelotropha+Aggregata, archigregarines, "aberrant archigregarines", "true" gregarines, cryptosporidia, and blastogregarines. However, resolution of the backbone increases with enlargement of alignment length or/and of taxonomic sample size and variety. A cladistic analysis of 25 morphological characters was performed. All morphological characters led to cladograms with several branches forming unresolved multifurcation. These cladograms correspond to the obtained molecular phylogenetic trees. However, when we use a strongly restricted set of characters, the cladograms demonstrate two traditional branches: gregarines and coccidia. We propose a scheme of Apicomplexa evolution with several independent and quickly evolving lineages (a star-like evolution model); at the same time two of them, Archigregarines and Blastogregarines, retain a set of ancestral morphological characters (morphostasis).