Phylogenetic analyses of the rhipicephaline ticks indicate that the genus Rhipicephalus is paraphyletic

We inferred the phylogeny of 21 species and subspecies of ticks from the su bfamilies Rhipicephalinae and Hyalomminae using cytochrome c oxidase subuni t I (COI) and 12S rRNA mitochondrial gene sequences. Two members of the sub family Haemaphysalinae were used for outgroup reference, The largest rhipic ephaline genus, Rhipicephalus, was represented by ticks from six of the spe cies groups, the second largest genus, Dermacentor, by species from two of three of its subgenera, and the genus Boophilus by 3 of its 5 species. We a nalyzed the 12S and COI sequences separately and together; statistically si gnificant incongruence between the 12S rDNA and the COI sequences was not d etected in the combined dataset using the incongruence length difference te st. The combined dataset provided greater phylogenetic resolution than the individual datasets, and although the 12S rDNA data had only 25% of the par simony-informative characters, it provided half of the total partitioned Br emer support for the combined dataset, We present the first hypothesis of p hylogenetic relationships among some species groups of Rhipicephalus but ou r most controversial result was that the genus Rhipicephalus is apparently paraphyletic, unless species of Boophilus are included in it. The species o f Rhipicephalus most closely related to Boophilus spp. were from the R. pra vus and R. evertsi species groups, which may implicate an African origin fo r this important group of ticks, (C) 2000 Academic Press.