Phylogeny of nuclear small subunit rRNA genes of hemogregarines amplified with specific primers.

Hemogregarines, apicomplexan intracellular blood parasites, are cosmopolitan in distribution and infect a broad range of vertebrate and invertebrate hosts. Molecular phylogenetic studies have been hampered by lack of hemogregarine-specific polymerase chain reaction primers that would allow amplification of parasite, but not host, DNA. A novel method for separating parasite and host 18S rRNA genes has been developed, and new primers that are specific for hemogregarine rRNA genes have been designed. These primers were used to obtain sequences from 4 isolates of hemogregarines of lizards from California, the Caribbean island of Grenada, eastern Australia, and Israel. Combining these results with already published sequences, a preliminary phylogeny of hemogregarines and several other apicomplexan taxa has been created. The hemogregarines form a monophyletic group and appear to be more closely related to coccidia than to Plasmodium species. The difficulty of using 18S genes that have multiple copies in some apicomplexan parasites was explored for systematic studies.