Question

You are studying a potential case of incipient sympatric speciation involving two morphs of a cichlid fish in a crater lake that feed at different depths and differ in morphology. If true, which of the following statements would make sympatric speciation more likely (or at least possible)?

1. The two morphs specialize on different food types; matings between the morphs produce offspring that are intermediate and can efficiently utilize both food types.

2. The two morphs feed on different food types and there is strong disruptive selection operating such that individuals that are intermediate are very strongly selected against (basically none survive).

3. Mating occurs in the area of the lake where each morph feeds. Also, females choose males based on jaw morphology, preferring males that have the same jaw morphology as the female.

4. The two morphs feed at different depths, but both morphs come to a rocky area near the shore to mate. Females prefer to mate with males of the other morph.

5. Genes for habitat preference and jaw morphology are very tightly linked to one another on a chromosome.

Answer 1

Several factors make sympatric speciation more likely in the case of the cichlid fish, including specialization on different food types and mate preference for different morphs.

Step-by-step explanation:

Sympatric speciation is the process by which new species evolve from a common ancestor without any geographic barriers. In the case of the cichlid fish in the crater lake, there are several factors that would make sympatric speciation more likely:

1. The first option, where the two morphs specialize on different food types and produce intermediate offspring that can efficiently utilize both food types.
2. The second option, where the two morphs feed on different food types and there is strong disruptive selection against individuals that are intermediate.
3. The fourth option, where the two morphs feed at different depths, but both come to a rocky area near the shore to mate. Females prefer to mate with males of the other morph.

All these scenarios involve a degree of reproductive isolation and the accumulation of genetic differences between the morphs, which are key factors in sympatric speciation.