AN ELECTROPHORETIC COMPARISON OF THE AUSTRALIAN PARALYSIS TICK, IXODES HOLOCYCLUS NEUMANN, 1899, WITH I-CORNUATUS ROBERTS, 1960 (ACARI, IXODIDAE)

An electrophoretic study was conducted on ticks morphologically identi fied as either Ixodes cornuatus or I. holocyclus from Tasmania and sev eral localities on mainland Australia. Ticks were characterised geneti cally at 27 enzyme loci encoding 24 enzymes. The extent of genetic div ergence (52-69% fixed differences) between ticks from Tasmania and tho se from the mainland was equivalent to that found between these two gr oups and two morphologically distinct species, I. hirsti and I. fecial is. The Tasmanian ticks therefore represent a different species from t he specimens from the mainland and the electrophoretic data show that the morphological characters currently used to distinguish I. holocycl us from I. cornuatus are inadequate. Genetic heterogeneity was detecte d in samples from different localities on the mainland. This could rep resent either population variation, or the existence of cryptic specie s, but more ticks from these mainland localities need to be examined e lectrophoretically to resolve this.