Host specificity in avian blood parasites: a study of Plasmodium and Haemoproteus mitochondrial DNA amplified from birds

A fragment of the mitochondrial cytochrome b gene of avian malaria (genera Haemoproteus and Plasmodium) was amplified from blood samples of 12 species of passerine birds from the genera Acrocephalus, Phylloscopus and Parus. B y sequencing 478 nucleotides of the obtained fragments, we found 17 differe nt mitocholdrial haplotypes of Haemoproteus or Plasmodium among the 12 bird species investigated. Only one out of the: 17 haplotypes was found in more than one host species, this exception being a haplotype detected in both b lue tits (Parus caeruleus) and great tits (Parus major). The phylogenetic t ree which was constructed grouped the sequences into two clades, most proba bly representing Haemoproteus and Plasmodium, respectively. We found two to four different parasite mitochondrial DNA (mtDNA) haplotypes in four bird species. The phylogenetic tree obtained from the mtDNA of the parasites mat ched the phylogenetic tree of the bird hosts poorly For example, the two ti t species and the willow warbler (Phylloscopus troclilus) carried parasites differing by only 0.6% sequence divergence, suggesting that Haemoproteus s hift both between species within the same genus and also between species in different families. Hence, host shifts seem to have occurred repeatedly in this parasite-host system. We discuss this in terms of the possilble evolu tionary consequences for these bird species.