An electrophoretic comparison of the Australian paralysis tick, Ixodes holocyclus Neumann, 1899, with I. cornuatus Roberts, 1960 (Acari : Ixodidae)

Abstract

An electrophoretic study was conducted on ticks morphologically identified as either Ixodes cornuatus or I. holocyclus from Tasmania and several localities on mainland Australia. Ticks were characterised genetically at 27 enzyme loci encoding 24 enzymes. The extent of genetic divergence (52–69% fixed differences) between ticks from Tasmania and those from the mainland was equivalent to that found between these two groups and two morphologically distinct species, I. hirsti and I. fecialis. The Tasmanian ticks therefore represent a different species from the specimens from the mainland and the electrophoretic data show that the morphological characters currently used to distinguish I. holocyclus from I. cornuatus are inadequate. Genetic heterogeneity was detected in samples from different localities on the mainland. This could represent either population variation, or the existence of cryptic species, but more ticks from these mainland localities need to be examined electrophoretically to resolve this.