A total-evidence phylogeny of ticks provides insights into the evolution of life cycles and biogeography

We inferred the phylogeny of 33 species of ticks from the subfamilies Rhipi cephalinae and Hyalomminae from analyses of nuclear and mitochondrial DNA a nd morphology. We used nucleotide sequences from 12S rRNA, cytochrome c oxi dase I, internal transcribed spacer 2 of the nuclear rRNA, and 18S rRNA. Nu cleotide sequences and morphology were analyzed separately and together in a total-evidence analysis. Analyses of the five partitions together (3303 c haracters) gave the best-resolved and the best-supported hypothesis so far for the phylogeny of ticks in the Rhipicephalinae and Hyalomminae, despite the fact that some partitions did not have data for some taxa. However, mos t of the hidden conflict (lower support in the total-evidence analyses comp ared to that in the individual analyses) was found in those partitions that had taxa without data. The partitions with complete taxonomic sampling had more hidden support (higher support in the total-evidence analyses compare d to that in the separate-partition analyses) than hidden conflict. Mapping of geographic origins of ticks onto our phylogeny indicates an African ori gin for the Rhipicephalinae sensu lato (i.e., including Hyalomma spp.), the Rhipicephalus-Boophilus lineage, the Dermacentor-Anocentor lineage, and th e Rhipicephalus-Booophilus-Nosomma-Hyalomma-Rhipicentor lineage. The Nosomm a-Hyalomma lineage appears to have evolved in Asia. Our total-evidence phyl ogeny indicates that (i) the genus Rhipicephalus is paraphyletic with respe ct to the genus Boophilus, (ii) the genus Dermacentor is paraphyletic with respect to the genus Anocentor, and (iii) some subgenera of the genera Hyal omma and Rhipicephalus are paraphyletic with respect to other subgenera in these genera. Study of the Rhipicephalinae and Hyalomminae over the last 7 years has shown that analyses of individual datasets (e.g., one gene or mor phology) seldom resolve many phylogenetic relationships, but analyses of mo re than one dataset can generate well-resolved phylogenies for these ticks. (C) 2001 Academic Press.