1.
Ideally, what two characteristics should a good species definition have? Most biologists agree that a species is the smallest evolutionarily independent unit. What, exactly, does evolutionary independence mean, and how does it occur?
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2.
Compare and contrast the biological, phylogenetic, and morphospecies concepts. On what criterion or criteria do they identify evolutionary independence? Are the definitions testable? For what groups do they work well? In what cases do they not work well? Explain how these definitions were used in the studies of copepod and African elephant diversity.
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3.
Outline the three general stages of speciation. Describe Mayr's general allopatric model of speciation. Which of the three general stages does this model describe? Compare and contrast dispersal and vicariance as mechanisms leading to geographic isolation. How these two hypotheses can be tested? Use the case studies of Hawaiian fruit flies and Central American snapping shrimp to illustrate.
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4.
Discuss the mechanism(s) by which a change in chromosome number may act as a barrier to gene flow. In what organisms is this mechanism thought to have been important, and what evidence supports this view? Is a difference in chromosome complement necessarily evidence that the change in chromosomes caused genetic isolation? Why or why not?
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5.
Discuss the potential role of genetic drift as a mechanism of genetic divergence among isolated populations. Under what conditions is drift thought to be most likely to lead to divergence? Are these conditions likely met in nature? Defend your answer. Is drift currently considered to make a major contribution to divergence and speciation? Why or why not?
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6.
Describe the role of natural selection as a mechanism of genetic divergence using apple and hawthorn maggot flies to illustrate your answer. What mechanism is thought to have isolated these populations? What evidence suggests that genetic divergence has occurred and that natural selection is the mechanism responsible? Is divergence due to host and/or habitat switching rare or common? Defend your answer.
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7.
Can sexual selection contribute to the genetic divergence of isolated populations? If so, is it likely to be any more or any less "efficient" than natural selection? Why or why not? Illustrate your answer using Hawaiian fruitflies, being sure to identify the key predictions and tests of the sexual selection hypothesis.
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8.
Explain Dobzhansky's hypothesis of reinforcement and its role in completing reproductive isolation between genetically divergent populations. If reinforcement acts, what kind(s) of isolating mechanisms should result? What kind(s) of isolating mechanisms might arise in the absence of reinforcement? Discuss evidence from lab, field, and modeling studies about the role and prevalence of reinforcement in completing reproductive isolation.
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9.
Do hybrid offspring between genetically divergent parents always have reduced fitness? Discuss Rieseberg et al.'s work on hybrid sunflowers and describe their evidence that hybridization may result in the formation of new species.
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10.
What is a hybrid zone? Compare and contrast the types of hybrid zones that may form when hybrids have lower fitness than parental forms, equal fitness to parental forms, or greater fitness than parental forms. Given the existence of a hybrid zone, how can these possibilities be distinguished? Explain using the hybrid zone between big sagebrush subspecies in Utah as your example.
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11.
Explain the reasoning behind the traditional view that a radical reorganization of the genome was necessary to produce new species. Is this view currently held? Why or why not?
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12.
Describe Via et al.'s studies of pea aphid populations and Schluter et al.'s studies of three-spined stickelback species. What pattern(s) of genetic divergence did the investigators find? What light do these studies shed on the genetics of speciation?
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