PHYLOGENETIC-RELATIONSHIPS AMONG TICK SUBFAMILIES (IXODIDA, IXODIDAE,ARGASIDAE) BASED ON THE 18S NUCLEAR RDNA GENE

Phylogenetic relationships among tick subfamilies have been estimated using morphological and molecular characters. However, the phylogeny b ased on a portion of the 16S mitochondrial rDNA gene differed from the morphologically based phylogeny in a number of important respects, Th e entire 18S rDNA gene was examined in 18 taxa from all tick subfamili es to test the 16S rDNA based phylogeny. The 18S phylogeny supports th e earlier 168 based phylogeny in placing members of Hyalomminae on a c ommon branch with members of the Rhipicephalinae and in indicating lon g branch lengths among soft tick taxa. However, unlike the 16S phyloge ny, Amblyomminae was monophyletic and members of Haemaphysalinae did n ot arise within Amblyomminae, Argasinae formed a monophyletic group wi thin Argasidae and was not a sister taxon of the hard ticks. In most r espects, the phylogeny based on the 18S rDNA gene resembles the morpho logically based phylogeny. (C) 1997 Academic Press.