Speciation

1. Speciation How are new species created?

2. Warmup: • Get out your learning targets paper • In the warmup section of your lab book: Create a concept map using at least 12 of the terms listed in part b) on the front side

3. Share current events article • Notes: • Directional selection, stabilizing, disruptive • Genetic Drift • Founder Effect • Speciation • Ensatinaeschscholtzii salamanders • Create a scenario… • Homework

4. Natural Selection on Polygenic Traits Low mortality, high fitness DirectionalSelection High mortality, low fitness Food becomes scarce • Individuals at one end of curve have higher fitness • Range of phenotypes shifts

5. Natural Selection on Polygenic Traits • Individuals near center of curve have highest fitness • Keeps center of curve at same position and narrows graph Stabilizing Selection Low mortality, high fitness High mortality, low fitness Selection against both extremes keeps curve narrow and in same place Percentage of Population Birth Weight

6. Natural Selection on Polygenic Traits Disruptive Selection Largest and smallest seeds become more common Population splits into two subgroups specializing in different seeds. Low mortality, high fitness Number of Birds in Population Number of Birds in Population High mortality, Low fitness Beak Size Beak Size • Individuals at upper and lower ends of the curve have higher fitness than individuals in the middle • Selection acts strongly against individuals of the intermediate type

7. Speciation • Speciation = formation of new species • Species = group of organisms that breed with one another and produce fertile offspring • As new species evolve, populations become reproductively isolated from each other

8. Isolating Mechanisms(lacewing interactive) • Behavioral Isolation • Differences in courtship rituals or other reproductive strategies • Geographic Isolation • Two populations separated by geographic barrier such as rivers, mountains or bodies of water • Temporal Isolation • Two or more species reproduce at different times of the day or year

9. Geographic isolation Behavioral isolation Temporal isolation Physical separation Behavioral differences Different mating times Reproductive Isolation results from Isolating mechanisms which include produced by produced by produced by which result in Independentlyevolving populations which result in Formation ofnew species

10. Speciation • In a phylogenetic tree, it is represented by a branching point • Example: Drosophila

11. A new species of fruit fly • Example: Fruit flies http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_42 A population of wild fruit flies on several bunches of rotting bananas, laying their eggs in the mushy fruit...

12. A new species of fruit fly • Disaster strikes: A hurricane washes the bananas and the fruit flies out to sea. The banana bunch washes up on an island off the coast of the mainland. The two portions of the population, mainland and island, are now too far apart for gene flow to unite them.

13. A new species of fruit fly • The populations diverge: Conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does. • Food preferences, and courtship displays change over the course of many generations of natural selection.

14. A new species of fruit fly • So we meet again: When another storm brings the island flies back to the mainland, they will not mate with the mainland flies since they've evolved different courtship behaviors. • The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations. • Two separate species now exist since genes cannot flow between the populations.

15. Geographic Isolation • Populations are separated by geographic change or dispersal to geographically isolated places • Rivers change course • Mountains rise • Continents drift • Organisms migrate • Roads are built • Note: a barrier for one species may not be a barrier for another species

16. Small populations face risks • Founder effect: when only a few individuals colonize a new place, genetic variation is low • Genetic drift: changes in gene pool due to chance (which individuals reproduce) • Bottleneck effect: disasters that eliminate a large number of individuals and greatly reduce the gene pool

17. Genetic Drift Section 16-2 Sample of Original Population Descendants Founding Population A Founding Population B

18. Genetic Drift Section 16-2 Sample of Original Population Descendants Founding Population A Founding Population B

19. Genetic Drift Section 16-2 Sample of Original Population Descendants Founding Population A Founding Population B

20. A new species: • If a group splits off from the main population • evolves to adapt to its environment • the changes accumulated make it unable to breed with the larger population • Then a new species has been formed

21. Other reasons for reproductive isolation: • Timing (Temporal Isolation): Different breeding seasons • Example: Spotted skunks • Western skunks breed in the fall, Eastern skunks breed in the late winter http://s190.photobucket.com/albums/z257/americanwildlife/Mammal/Z-western-spotted-skunk1.jpg http://www.redorbit.com/modules/reflib/article_images/42_7de29e7e859b48896129c3d380d3cfbb.jpg

22. Other reasons for reproductive isolation: • Behavior (Behavioral Isolation): Different courtship or mating behaviors • Example: Eastern and Western Meadowlarks • Different songs

23. Other reasons for reproductive isolation: • Habitat: Adapted to different habitats in the same general location • Example: Stickleback fish in British Columbia • Live in different levels of water, have different diets http://ecoreb.org/imgs/o_gasacu2.jpg

24. Other reasons for reproductive isolation: • Others: different reproductive structures, insects only transfer pollen to certain plants, hybrid offspring is sterile http://www.birkenholz.com/IMAGES/MuleColt05Right.jpg

25. Speciation of Darwin’s Finches • Founders Arrive • Separation of Populations • Changes in the Gene Pool • Reproductive Isolation • Ecological Competition • Continued Evolution

27. Speciation in the Andes (Ecuador) • Hummingbird video • Explain the hypothesis presented by the scientists profiled in this segment to explain the process of speciation in hummingbirds and possibly other species. • How does this hypothesis differ from the traditional view that speciation often requires geographic separation of populations? • Why were the researchers collecting blood from the populations they studied? Discuss at least two possible analyses that could be performed on those samples and, identify at least two different questions that might be answered with sufficient data.

28. Ensatina Salamanders • California salamanders • Live and lay eggs on land • Studied by R.C. Stebbins in the 1940s • You used his data to map the locations of various subspecies • Video of mating behavior: • http://evolution.berkeley.edu/evolibrary/article/0_0_0/devitt_07 • Pictures of each subspecies: • http://www.indiana.edu/~ensiweb/lessons/stepsal4.html http://evolution.berkeley.edu/evolibrary/article/0_0_0/devitt_02

30. Ring Species • All subspecies interbreed with their immediate neighbors EXCEPT at southern end • E. klauberi and E. eschscholtzii do not interbreed • Where should speciation be marked? http://evolution.berkeley.edu/evolibrary/article/side_0_0/biospecies_01#ring

31. Did you get it? Watch this! • Link to video about Ensatina salamanders in California (3 minutes) http://www.youtube.com/watch?v=PjcFSy1KCTI

32. Do Now! • Devise a scenario in which a particular type of selection leads to speciation. • Use the 5 tenants of natural selection • What type of selection is at work?

33. Homework • Read section 17-4 in your textbook (pg. 435-440), Patterns in Evolution • Answer the three learning targets for this section (#3, 4 and 5 under chapter 17) from your LEARNING TARGETS paper.