It is often difficult to disentangle the roles of environmental factors and mating prefere...

It is often difficult to disentangle the roles of environmental factors and mating preferences in creating and maintaining species boundaries. This is why the cichlid example in Section 16.3 is so unique, and also why it can be difficult to understand. Study Figure and answer the following questions by comparing the two most extreme island habitats of Marumbi (left column) and Makobe (right column):

Figure Speciation by sensory drive in cichlids Among five different islands, as water clarity increases (left to right), (a) male color and depth distribution become increasingly divergent betweenthe two species, as does (b) LWS opsin allele frequency. (c) Finally, females from an island with clearer water showed much stronger color preferences in mates (right graph) than females from an island with murkier water (left). Redrawn from Seehausen et al. (2008).

a. How do the two environments differ?

b. What color are the male fish in these two habitats, and at what depth are the different colors of male fish found?

c. What LWS opsin alleles are present in the two populations, and what does it mean for a female to have a “blue” or a “red” LWS opsin allele? Finally, ask yourself why the environmental context is so important for these cichlids. What colors of male fish would be present in Lake Victoria if all habitats were similar to Marumbi (low water clarity)?