A drought hits the habitat of a semi-aquatic bird population. All ponds dry up, and fish populations decline. There are two groups of birds in the population that differ in leg length and diet. Long-legged birds eat fish, while short-legged birds eat insects. The drought has little effect on insect populations.
What is the main selective pressure in this scenario?
The main selective pressure in this scenario is the availability of food, specifically the decline in fish population. The birds with long legs, which primarily eat fish, will struggle to find enough food to survive and reproduce. This will exert a selective pressure on the population, favoring individuals with shorter legs that can adapt to eating insects, which are still available in sufficient numbers. Therefore, the correct answer is B. fish population.
