Two hundred years ago, the fly species Rhagoletis pomonella only laid its eggs on fruit of the hawthorn tree. Today, different "host races" of R. pomonella lay their eggs on hawthorns OR apples. Apples occur within the range of hawthorns, so divergence between apple flies and hawthorn flies could be the first step in sympatric speciation. Choose the evidence that would suggest that R. pomonella is currently undergoing sympatric speciation. Check all that apply.A) Apple flies typically mate with apple flies, and hawthorn flies typically mate with hawthorn flies.B) Apple flies and hawthorn flies emerge from their hosts at different times of the year.C) Apple flies and hawthorn flies are able to form fertile hybrids.D) Apple flies and hawthorn flies are physically indistinguishable

Question

from each other.

What will be an ideal response?

Answer 1

A, B

Clarify Question
• What is the key concept addressed by the question?
        o This question addresses sympatric speciation.
• What type of thinking is required?
        o This question is asking you to analyze the information given, using logic, to dissect the problem and determine the answer.

Gather Content
• What do you already know about sympatric speciation?
        o Sympatric speciation is speciation that occurs without geographic separation.
        o Sympatric speciation can occur either instantaneously or over the course of multiple generations.
        o Instantaneous speciation generally involves polyploidy and is typically found in plant species.
        o Slower sympatric speciation can occur due to disruptive selection, causing a population to contain individuals exhibiting two different phenotypes. For instance, character displacement causes individuals to favor different resources, minimizing competition. This can lead eventually to speciation.

Choose Answer
• Given what you now know, what information and/or problem-solving approach is most likely to produce the correct answer?
        o The pieces of evidence that support the occurrence of sympatric speciation are:
        o Apple flies typically mate with apple flies, and hawthorn flies typically mate with hawthorn flies.
        o Apple flies and hawthorn flies emerge from their hosts at different times of the year.
        o Both of these indicate that the host preference is leading to less interbreeding between the two populations.

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 The question required you to analyze the information given, using logic, to dissect the problem and determine the answer.
        o Did you recognize that a host preference can drive sympatric speciation, particularly if the adults are ready to mate at different times, and typically mate only with flies on the same host?