Isolation by distance in Texas populations of Rhipicephalus microplus ticks collected during two years of high infestation rates, a) 2008 and b) 2009. Open grey circles denote all possible pairwise comparisons of ticks from all hosts (cattle and white-tailed deer [WTD]). Closed red triangles denote comparisons among ticks from WTD only. Pairwise FST estimates from FSTAT (θ) were transformed to FST /(1- FST) according to the method of Rousset . The regression line (solid black line) and bootstrapped 95% confidence limits for slope (dashed lines) were calculated using reduced major axis (RMA) regression in the IBD program . The regression equation is only provided for “all” comparisons.