Genetic variation in the 16s mitochondrial rDNA gene from Texas and Oklahoma populations of Amblyomma maculatum



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Single-strand conformation polymorphism was used to detect different haplotypes of the 16S mitochondrial rDNA gene within samples of Gulf Coast ticks, Amblyomma maculatum Koch, collected from Payne County, Oklahoma and Brazos and Refugio Counties, Texas. Ticks were collected from dogs, horses, and cattle. The haplotype frequencies from the cattle collections were compared to a similar study, conducted in 1999, to detect if any changes in frequencies had occurred. There were significant differences (p<0.05) between the haplotype frequencies from 1999 and 2007. The haplotype designated as D was highly prevalent in all sampled populations, however was not detected in Oklahoma and Texas eight years earlier. Possible explanations for this occurrence include ticks with this haplotype having a higher fecundity, resistance to drought, or resistance to acaricides. Comparisons of the haplotypes of ticks collected from cattle solely in 2007 showed that the haplotype frequencies of Brazos County and Payne County are more similar than to Refugio County. The haplotype frequencies found on various hosts were also compared and no significant differences were found (p>0.05).