In their 2008 Paper Hanifin Brodie and Brodie looked at the

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?

Solution

A. Newts species contains a soecific toxin called Tetratoxin which is dangerous for other organisms. This toxin helps the garter snake to taste the Newts speicies. Because of continued preying of such Newts the garter snake develpos resistance by forming sodium channels to digets the tetratoxin.Both Newts and snakes toxicity and resitance varies with space or location some being cold spots and some being hot spots.When toxicity and resistance are positively corelated then the existence of coevolution takes place. In the above graph the coevolution will be stong in B as both are positively corelated. In A the snakes will be whinning and in C the Newts will be whinning because the snakes when taste the newst for first time they feel awfull which make the snake to whinning due to attack of toxin on muscles and they become resistance to the newts.

B. In Population A since the prey toxicity and resitence are not positively corelated so the occurrence of coevolution is not not possible. There is geographical ranges which dont allow the prey and predator to harm each other leads to covolutionary arm races in which prey is not able to produced the amount of toxin that would harm the predator and predators are out of reach to come into the affects of such toxins