Evolution of ticks.

Evolutionary patterns in ticks have traditionally been cast in terms of host associations. Largely untested assumptions of cospeciation and observations of current host associations are used to estimate the age of different taxa. Several recent phylogenetic studies of supraspecific relationships in ticks, based on both morphological and DNA-sequence data, allow the first rigorous testing of these assumptions. Reanalysis of patterns of tick-host associations suggests that the perception of host specificity in ticks may be an artifact of incomplete sampling. An analysis of tick-host and -habitat associations and biogeographical patterns, in the context of the newly derived phylogenies, suggests that much of the existing host-association patterns may be explained as artifacts of biogeography and ecological specificity.