Garter snakes have evolved resistance to the poisonous secretions of the rough-skinned newts. The following figure describes poison production in newts and the resistance (measured as amount of poison tolerated) in garter snakes in three different geographical areas. Given this information, which of the following statements is correct regarding the evolution of poison resistance in garter snakes?
The question asks about the evolution of poison resistance in garter snakes concerning the toxic secretions of rough-skinned newts.
Evolutionary Arms Race Dynamics
The relationship between garter snakes and rough-skinned newts is a classic example of an evolutionary arms race. Garter snakes evolve resistance to the newt's poison, while newts evolve increased toxicity. This implies strong selective pressures.
Analyzing Resistance Mechanisms
- Poison Production (Newts): Newts produce tetrodotoxin (TTX), a potent neurotoxin.
- Resistance (Garter Snakes): Garter snakes evolve resistance, allowing them to tolerate higher doses of TTX. This resistance often involves genetic mutations affecting sodium channels, which TTX targets.
Evaluating the Options
- Option 1: Evolution of resistance is neutral. This is incorrect. Resistance provides a significant survival advantage against predation (or in this case, prey consumption) and is therefore subject to strong natural selection, not neutrality.
- Option 2 & 3: Snakes in Area X are more/less adapted. While different geographical areas might show varying levels of resistance and toxicity due to local pressures, these statements make specific comparative claims that depend entirely on the visual data in the figure, which is not provided. However, the core concept of adaptation is relevant. High resistance indicates adaptation to toxic prey.
- Option 4: The resistance mechanism is costly. This statement reflects a fundamental principle in evolutionary biology. Developing resistance to toxins often requires significant physiological or metabolic changes. These changes can impose a "cost of resistance," meaning the snake may expend more energy on detoxification, have altered cellular functions, or experience reduced fitness in other areas (like growth rate or reproductive success) compared to non-resistant snakes in a non-toxic environment. This trade-off explains why resistance might not evolve or be maintained in all populations if the selective pressure isn't sufficiently high.
Conclusion
The most accurate general statement, consistent with evolutionary principles of toxin resistance, is that the mechanism imposing resistance carries a cost. This cost is balanced against the benefit of surviving encounters with toxic prey.
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