Courtship for Anolis lizards involves the male displaying a dewlap (skin under the throat area) that varies in appearance based upon the species. Lizards that are found in darker, more shaded environments will have dewlaps that are lighter in color because they are more noticeable by potential mates. Which of the following mechanisms best explains how speciation is at work in this example?

Question

A.  Postzygotic isolation
B.  Reinforcement
C.  Genetic drift
D.  Natural selection

Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
 
Gather Content/Choose Answer
· What do you already know about speciation? What other information is related to the question?
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?

Answer 1

D.  Natural selection

Clarify Question
· What is the key concept addressed by the question?
        o Mechanisms that lead to speciation.
· What type of thinking is required?
        o The question is asking you to analyze a situation that leads to speciation in lizards.
 
Gather Content/Choose Answer
· What do you already know about speciation? What other information is related to the question?
        o To solve this problem, you’ll need to remember that speciation can occur for many reasons. Usually some form of isolation is involved leading to reproductive isolation. Examples are ecological, temporal, mechanical, and behavioral isolations. When members of a species become isolated they are frequently also undergoing selection which encourages the speciation.
 
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
        o If you figured out the correct answer, good job! If not, where did you go wrong? Did you think that genetic drift is at work in this example? While it is true that genetic drift can lead to speciation, this example is looking at changes in the environment rather than very small populations sizes. Did you think that postzygotic isolation is a possibility here? This is an example of a prezygotic isolation rather than a postzygotic isolation. How about reinforcement? That would apply if the lizards had hybrids that were less successful which isn’t mentioned in the question (and doesn’t apply here). That leaves natural selection which would explain that there is a mating preference for being able to clearly see colors of the male dewlaps.