In their 2008 paper, Hanifin, Brodie, and Brodie looked at the co evolution of a newts (Taricha spp., top picture) and one of their potential predators, the common garter snake (Thamnopis sirtalis). The graph below shows the relationship between the amount of toxin in the skin of the newts and the garter snakes resistance to the toxin at a given location. The dashed line represents a reduction of 50% in the snake's health. Some locations may be considered co-evolutionary hot-spots, where reciprocal selection is strong Other locations are co-evolutionary cold spots, where the traits of one species don't match with the other and one species is "winning" the interaction. The letters on the graph represent 3 locations with snakes and newts.
a. In which of the three locations (if any) is co-evolution strong? In which locations (if any) is the snake "winning"? In which locations (if any) is the newt winning? Explain your reasoning.
b. What might be an explanation for the dynamics occurring in population A, where the newt hasn't evolved toxicity and the snake hasn't evolved resistance. In other words, what might prevent a co-evolutionary arms race from occurring in this system?