Speciation

1. Speciation Creation of Unique Gene Pools

2. I. Introduction • A. Microevolution vs. macroevolution • 1. microevolution • a. Definition • b. Example • c. Importance in evolutionary process • d. Can be seen • e. Measurable • f. Natural selection

3. 2. macroevolution • a. evolution or creation of new taxonomic groups • b. Novel innovations • c. New ways of making living • d. Branching of phylogenetic tree • e. Evolution of coelom • f. May not occur by natural selection • g. Harder to understand

4. B. Speciation events may drive macroevolution • 1. New species may be first of a new grade or branch • 2. Two modes of speciation observed in fossil record • a. anagenesis • b. cladogenesis

5. C. Anagenesis-gradualism • 1. species seem to slowly gradually change • 2. from one springs another • 3. driven by natural selection • 4. not as often seen in the fossil record

6. D. Cladogenesis • 1. branching pattern • 2. rapid speciation event • 3. punctuated equilibrium • 4. supported by many records in fossil

7. II. What is a species? • A. Morphological species concept • 1. places specimen together or separates them on structural basis • 2. convenient when working in a lab • 3. fossil organisms • 4. organisms that don’t come into contact

8. B. Biological species concept • 1. definition • 2. particularly good definition for population genetics • 3. speciation occurs when two gene pools become separate and distinct

9. III. How does speciation occur A. Allopatric speciation 1. barrier 2. gene flow interupted 3. differences accumulate 4. when become sympatric?

10. 5. Generalizations • a. Requires a lot of time generally • b. Most often occurs in small populations • c. What is barrier to one may not be barrier to another • d. Adaptive radiation example of allopatric speciation • e. End point of speciation event is hard to agree to • f. Most common?

11. B. Parapatric speciation • 1. two populations sort of separated • 2. experience different selection pressures at edges of range • 3. differences accumulate despite gene flow • 4. gene flow becomes impossible

12. C. Sympatric speciation • 1. most commonly seen in plants • 2. common barrier to hybridization is meiotic failure of hybrid • a. Two distinct sets of chromosomes • b. No homologous pairs • c. What happens at prophase I of meiosis

13. 3. Polyploidy occurs commonly in plants • a. Haploid • b. Diploid • c. Polyploid • d. Generally leads to sterility • e. But in plants

14. 4. Allopolyploidy

16. 4. New species form this way in plants because they self pollinate

17. 5. Very uncommon in animals-cichlids

18. 6. Parasites and hosts-apple maggot fly

19. Flies tend to stay on host

20. V. Pre and postzygotic barriers to hybrid formation • A. Natural selection operates to maintain separate gene pools when speciation has occurred • 1. Imagine disruptive selection • 2. Specializations occur • 3. Overlap after speciation event • 4. Potential interbreeding • 5. Parental species have specialized • 6. Hybrids dilute the specializations • 7. Natural selection would come down hard on the dilution

21. B. Prezygotic barriers • 1. Habitat isolation

22. 2. Behavioral isolation

23. Spotted Newts

24. Spermatophore and red eft

25. 3. Temporal isolation

26. 4. Vocalizations Eleutherodactylus coqui

27. 5. Mechanical Isolation

28. Kangaroo penis types

29. Adapters?

30. C. Postzygotic barriers to hybridization • 1. hybrid inviability • 2. hybrid sterility • 3. hybrid breakdown-F2 are sterile

31. D. Thought questions • 1. Do prezygotic or postzygotic barriers to hybrid formation form first? • 2. Which of these two mechanisms is favored by natural selection? • 3. Which of these two methods is more cost effective?

32. VI. Potential forces behind macroevolutionary change • A. Chance • 1. cannot be preadapted to a disaster • 2. meteorite implosion will wipe out all but lucky few • 3. who survives can direct future evolutionary paths

33. B. Macromutations • 1. translocations

34. 2. Inversions

35. 3. Chromosomal duplications

36. C. Segmentation genes • 1. ancestral animals were one continuous body piece • 2. the evolution of segmentation genes produced a branch in the tree of life • 3. segmentation of body parts allows specializations to occur in different regions of the body • 4. feeding structures and locomotion appendages

37. D. Homeotic genes • 1. specify developmental plan for each segment • 2. mutations can cause one body part to be replaced by a second • 3. leg growing from head

38. E. Hox genes control number of appendages • 1. ancestral fruit fly had four wings • 2. more economical and faster to fly with two wings • 3. mutation in Hox genes can cause backward jump • 4. devolution

39. F. Allometric growth • 1. varied growth rates for different parts of the body during development

40. 2. Mutation in the genes which govern allometric growth • Might produce chances for rapid evolutionary chanage • Growth rates altered, drastic changes in shape • May or may not be adaptive

41. Ocean sun fish

42. G. Changes in timing of development-paedomorphsis • 1. retention of larval characteristics into adulthood • 2. aquatic salamander • 3. by being able to remain in water may have escaped terrestrial predators • 4. aquatic environment is not as harsh-may have escaped dessication • 5. genes that cause metamorphosis may have been blocked • 6. adult neotenic salamanders given injections may display adult traits

43. H. Neoteny –retention of juvenile traits into adulthood

45. H. Old genes being turned back on • 1. modern birds lack teeth • 2. aerodynamically not efficient • 3. ancestral birds had teeth • 4. genes for teeth still reside in bird chromosomes • 5. unlock the past-raw material for future evolutionary jumps?

46. Inbreeding

47. I. Jumping genes-transposons

48. J. Viral transmission