highly significantp < 0.001
This effect of upper spines was highly significant (χ 2 = 94.39, p < 0.001), whereas the presence of lower spines (χ 2 = 0.014, p = 0.90) and the interaction between upper and lower spines (χ 2 = 0.035, p = 0.85) had no discernible effects on dispersal. 3.3 Experiment 3: Dispersal by cars Upper spines facilitated the probability and distance of dispersal by cars.