Comparison of the isozyme phenotypes of the morphologically similar ticks Amblyomma cajennense and A. imitator (Acari: Ixodidae) from south Texas.

A survey of Amblyomma Koch tick populations in southern Texas revealed that A. imitator Kohls was restricted to the two most southern counties, but that A. cajennense (Fabricius) ranged at least as far north as Kingsville, Tex. Females of the two species could be distinguished by the presence of chitinous tubercles on the festoons of A. cajennense and the presence of projections over both sides of the apron of the genital aperture in A. imitator. Males were distinguished by size, ornamentation, and the elongate ventral scutes of A. imitator. In addition, six enzymes, AATA, ACONA, IDH2, LDH, MPI, and PEP, were diagnostic for the two species and two others, aGPD and ACONC, had high diagnostic values. Resulting interspecific divergence was significant, I = 0.582. Genetic variability was higher in A. imitator (h = 0.092) than in A. cajennense (h = 0.057), but neither species exhibited marked interpopulation divergence (I = 0.991 in A. imitator, I = 0.994 in A. cajennense).