A REEVALUATION OF RELATIONSHIPS IN THE METASTRIATA (ACARI, PARASITIFORMES, IXODIDAE)

A systematic analysis of generic/subgeneric relationships in the ixodi d lineage Metastriata was conducted based on 82 structural and develop mental characters, 15 of which have multiple states. Results of the an alysis show considerable agreement with current classifications of the Ixodidae, including good support for monophyly of the Metastriata, th e genera Ixodes and Haemaphysalis, and the grouping of Hoogstraal's Rh ipicephalinae and Hyalomminae, and fair support for the genus Hyalomma . Our results differ from these classifications most notably by reject ing monophyly of the genera Aponomma and Amblyomma. Instead, the analy sis provides weak support for a hypothesis in which the basal two to t hree lineages in the Metastriata are all composed of Aponomma species, and in which a fourth lineage within that genus, Aponomma elaphense, clusters with Amblyomma quadricavum to form a more derived lineage. Re solution is insufficient to support or reject monophyly of the genera Dermacentor and Rhipicephalus, or to resolve the position of the genus Haemaphysalis relative to the other Metastriata. Overall resolution w ithin the Rhipicephalinae/Hyalomminae is quite good, but it is quite p oor among the Amblyomminae and Haemaphysalinae. These results are simi lar to the results of recent 16S and 18S rDNA based molecular analyses . There are few indications of host specificity among the lineages ana lysed. The basal metastriate lineages contain a large number of squama te associates, but the pattern is not sufficiently clear to reject the hypothesis that these ticks will feed on all available vertebrate hos ts. On the other hand, nearly all of the basal taxa are Australian. Th is suggests a possible origin of the Metastriata in Australia, with su bsequent dispersal to other parts of the world.