Chapter 15: Mechanisms of Speciation

1.	What does it mean to say that species are "evolutionarily independent" or that "species form a boundary for gene flow?" [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
2.	Why might dispersal or vicariance events initiate speciation? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
3.	Draw an evolutionary tree. Circle at least five monophyletic groups. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
4.	What does "sex" consist of in bacteria? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
5.	Explain the difference between dispersal and vicariance. Why do populations that are isolated in distinct geographic areas tend to become different species over time? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
6.	How does polyploidy occur? Why do tetraploid populations tend to be reproductively isolated from closely related diploid populations? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
7.	What are the possible outcomes when species that have long been separated geographically come back into contact and begin hybridizing? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
8.	What is reinforcement? Is it an example of genetic drift, natural selection, or sexual selection? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
9.	Compare and contrast the biological species concept, the morphospecies concept, and the phylogenetic species concept. What criterion does each use to identify species? What are the pros and cons of each? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
10.	The text introduces work on speciation in marine copepods and African elephants. In each case, did application of the phylogenetic species concept lead to the recognition of fewer, the same, or more species? Explain. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
11.	When the Panama land bridge between North and South America was uncovered, some North American mammal lineages crossed to South America and underwent dramatic radiations. For terrestrial species, did the completion of the land bridge represent a vicariance or dispersal event? Does the recent building of the Panama Canal represent a vicariance or dispersal event for terrestrial organisms? For marine organisms? Briefly outline one experiment that would test whether the Panama Canal is affecting speciation in a terrestrial or marine species. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
12.	Morphologically similar species of snapping shrimp that are each others' closest relatives live on either side of the Isthmus of Panama. Why does this observation support the hypothesis that speciation occurred via vicariance? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
13.	Phylogenetic analyses show that in many cases, closely related Hawaiian species occur in the following pattern: The more ancestral groups occupy older islands in the archipelago, while the more derived populations occupy younger islands. Why does this observation support the hypothesis that speciation has occurred via dispersal? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
14.	Why is sexual selection considered a particulary effective process in producing speciation? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
15.	Researchers are claiming that benthic and limnetic three-spined sticklebacks and red clover and alfalfa populations of pea aphids are speciating due to natural selection. Do you agree with this hypothesis? Why or why not? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
16.	Within the past 50 years, soapberry bug populations in the United States have diversified into populations distinguished by markedly different beak lengths. These bugs eat the seeds at the center of soapberry fruits. Native and recently introduced varieties of soapberries differ greatly in fruit size. Describe the experiments or observations you would make to launch an in-depth study of speciation in these bugs. What data would tell you whether they are separate populations evolving independently, or a single interbreeding population? Many museums contain insect specimens from decades ago. What would you examine in these old specimens? What information about the host plants would be useful? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
17.	Red crossbills are small finches specialized for eating seeds out of the cones of conifer trees. They fly thousands of kilometers each year in search of productive cone crops. Despite their mobility, crossbills have diverged into several "types" that differ in bill shape, body size, and vocalizations. Each type prefers to feed on a different species of conifer, and each species of conifer is found only in certain forests. Bill size and shape affects how efficiently a bird can open cones of a certain conifer species. Explain how a highly mobile animal such as the red crossbill could have diverged into different types in the absence of any geographic barrier. How could you test your ideas? If crossbills could not fly, do you think speciation would occur more quickly or more slowly? If conifer species were not patchily distributed (i.e., in different forests), do you think crossbill speciation would occur more quickly or more slowly? In general, how do habitat patchiness and dispersal ability interact to affect divergence? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
18.	Ellen Censky and coworkers (1998) recently documented the arrival of a small group of iguanas to the Caribbean island of Anguilla, which previously had no iguanas. The animals were carried there on a raft of fallen trees and other debris during a hurricane. Outline a long-term study that would document whether this newly isolated population diverges from iguanas on nearby islands to form a new species. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
19.	Would glaciation in northern Europe and North America have created vicariance events over the past 150,000 years? If so, how? Which organisms might have been affected? For example, consider the different effects glaciation might have on small mammals, migratory birds, and trees. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
20.	A total of 30 different species of yuccas are found in the deserts of the American Southwest. Yuccas are pollinated when female moths lay their eggs near the egg cells of yucca plants and male moths visit to fertilize the moth eggs. Traditionally, just one species of moth was thought to pollinate all 30 species of yucca. Jim Leebens-Mack and co-workers (1998) studied the moths that pollinate two different yucca species, however, and found that the moths are morphologically distinct and form independent tips on a phylogeny. Are these moths different species? How would you go about testing the hypothesis that each species of yucca is pollinated by a different species of moth? [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.
21.	At least eight geographically isolated populations of the spiny lizard Sceloporus jarrovii exist in the mountains and deserts of north and central Mexico. Although females look similar, males in each population are strikingly different—ranging in color from jet black to gold to green, orange, and blue. An analysis by John Wiens and colleagues (1999) has shown that at least five of the populations are phylogenetic species. Would they be considered species under the morphospecies and biological species concept as well? Wiens and co-workers suggest that sexual selection has been responsible for speciation in this group. Outline a study that would test this hypothesis. [Hint] To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.