Exam 24: Speciation

Which of the following is true regarding speciation by polyploidy?

Use the following information when answering the corresponding questions). About 3 million years ago, the Isthmus of Panama a narrow strip of land connecting North and South America) formed, divid marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sid isthmus. Based on the morphospecies concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629- 32.) -If the isthmus formed gradually rather than suddenly, what pattern of genetic divergence would you expect to find in these species pairs?

Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of closely related tree frogs in South America. If reinforcement of prezygotic isolation is occurring, what would you expect if you compare the calls of the two species in zones of sympatry versus zones of allopatry?

Which of the following reproductive barriers would prevent a hybrid zygote from developing into a viable, fertile adult?

The two populations are

A storm brings two formerly separated populations of beetles together. They look very similar. Under the biological species concept, which of the following would show that the two populations are different species?

You are studying lizards in the field. The range of the northern population, species 1, overlaps the range of the southern population, species 2. You find hybrids in the zone of overlap. What is happening?

You want to study divergence of populations, and you need to maximize the rate of divergence in order to see results within the period of your grant funding. You will form a new population by taking some individuals from a source population and isolating them so the two populations cannot interbreed. What combination of characteristics would maximize your chance of seeing divergence in this study? 1) Choose a random sample of individuals to form the new population. 2) Choose individuals from one extreme to form the new population. 3) Choose a species to study that produces many offspring. 4) Choose a species to study that produces a few, large offspring. 5) Place the new population in the same type of environment as the source population. 6) Place the new population in a novel environment compared to that of the source population.

Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of closely related tree frogs in South America. What outcomes can occur where the ranges of two species overlap?

If a plant species with 2n = 14 forms an allopolyploid with a plant species with 2n = 18, what would be the likely diploid 2n) number of the allopolyploid?

Use the following information when answering the corresponding questions). About 3 million years ago, the Isthmus of Panama a narrow strip of land connecting North and South America) formed, divid marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sid isthmus. Based on the morphospecies concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629- 32.) -The sister populations on opposite sides of the isthmus are true species under which species concept?

You are studying two populations of spiders of the Dolomedes genus, characterized by a light stripe down each side of the body. One population lives in a pond, while another nearby population lives in the trees. Which of the following species concept would you be using if you determined that these were two different species?

Why is speciation by polyploidy more likely in plants than in animals?

Many songbirds breed in North America in the spring and summer and then migrate to Central and South America in the fall. They spend the winter in these warmer areas, where they feed and prepare for the spring migration north and another breeding season. Two hypothetical species of sparrow, A and B, overwinter together in mixed flocks in Costa Rica. In spring, species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species?

A population of ground squirrels is separated by a glacier. Changes in which of the following would most likely result in reproductive isolation if the two populations came into contact several generations later?

The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when they mate among themselves, they are rarely successful in producing offspring. What can you infer from this information?

Imagine two North American ground cricket species that contact each other as the southern species moves northward during a period of global warming. These two species do not mate much, due to differences in their courtship songs. The northern cricket does not seem to tolerate the warmer temperatures well, but is limited in its ability to move north because it does not normally disperse much. Based on this information, which is the most likely outcome?

A small number of birds arrive on an island from a neighboring larger island. This small population begins to adapt to the new food plants available on the island, and their beaks begin to change. About twice a year, one or two more birds from the neighboring island arrive. What effect do these new arrivals have?

Which of the following does not tend to promote speciation?

Two researchers experimentally formed tetraploid frogs by fertilizing diploid eggs from Rana porosa brevipoda with diploid sperm from Rana nigromaculata. When they mated these tetraploid frogs with each other, most of the offspring that survived to maturity were tetraploid, with chromosome sets of both diploid parent species. Based on these results, if this type of tetraploid formed in the wild, what would be the result? Y. Kondo and A. Kashiwagi. 2004. Experimentally induced autotetraploidy and allotetraploidy in two Japanese pond frogs. Journal of Herpetology 383):381- 92.)