1. Chapter 24 The Origin of Species

2. Hummingbirds of Costa Rica Species

3. Biological Species Concept Species A population whose members can potentially interbreed in nature to produce viable, fertile offspring In practice, we recognize two populations as separate species if each has distinguishing characteristics relative to the other, and members of each population lack the potential to interbreed in nature with members of the other population

4. Reproductive Barriers A complete barrier would result in no gene flow An incomplete barrier could still reduce gene flow Isolate populations from one another

5. Reproductive Barriers Pre-zygotic vs. post-zygotic A complete barrier would result in no gene flow An incomplete barrier could still reduce gene flow

6. Reproductive Barriers Pre-zygotic Habitat isolation Geographic isolation Roseate spoonbill Eurasian spoonbill

7. Pre-zygotic Habitat isolation Geographic isolation Reproductive Barriers North America Central America Madagascar

8. Reproductive Barriers Pre-zygotic Habitat isolation Geographic isolation Ecological isolation Hawthorns or apples for oviposition Rhagoletis pomonella

9. Reproductive Barriers Pre-zygotic Habitat isolation Geographic isolation Ecological isolation Behavioral (mate choice) isolation

10. Blue-footed boobies Red-footed booby Galapagos Islands

11. Satin Bowerbirds & their bowers Tooth-billed Catbird’s leaf display Australia

12. Reproductive Barriers Pre-zygotic Habitat isolation Geographic isolation Ecological isolation Behavioral (mate choice) isolation Temporal isolation

13. Periodical (12 year) Dog-day (17 year)

14. Reproductive Barriers Pre-zygotic Habitat isolation Geographic isolation Ecological isolation Behavioral (mate choice) isolation Temporal isolation Mechanical isolation

15. C. wapleri Thompson Creek, W. Feliciana Parish

16. Reproductive Barriers Pre-zygotic Habitat isolation Geographic isolation Ecological isolation Behavioral (mate choice) isolation Temporal isolation Mechanical isolation Gametic isolation

17. acrosome head midpiece tail ovum

19. Buffon (1811)

20. Reproductive Barriers Post-zygotic Reduced hybrid viability Reduced hybrid fertility Hybrid sterility (in the extreme)

21. x= sterile ♀ ♂

22. Reproductive Barriers Post-zygotic Reduced hybrid viability Reduced hybrid fertility Hybrid sterility (in the extreme) Hybrid breakdown (reduced viability or fertility occurs in the offspring of hybrids)

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 24.4 Individuals of different species Mating attempt Habitat isolation Temporal isolation Behavioral isolation Mechanical isolation HABITAT ISOLATION TEMPORAL ISOLATIONBEHAVIORAL ISOLATION MECHANICAL ISOLATION Reproductive Barriers

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Viable fertile offspring Reduce hybrid viability Reduce hybrid fertility Hybrid breakdown Fertilization Gametic isolation GAMETIC ISOLATION REDUCED HYBRID VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN Reproductive Barriers Figure 24.4

25. Speciation The process by which new species form Two requirements: Reproductive isolation of populations (gene flow sufficiently reduced) Genetic divergence (divergent evolution) Two main modes: Allopatric vs. sympatric

26. Allopatric speciation Divergence occurs in geographic isolation

27. Sympatric speciation Divergence occurs despite lack of geographic isolation

28. Allopatric vs. sympatric speciation Figure 24.5

29. Hawthorns or apples for oviposition Rhagoletis pomonella Sympatric speciation

30. Divergence occurs despite lack of geographic isolation Polyploids Organisms with extra sets of chromosomes; can result in sympatric speciation in one generation The origin of a polyploid individual is usually a mistake in meiosis or mitosis Autopolyploidy vs. allopolyploidy

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An autopolyploid Is an individual that has > two chromosome sets, all from a single species Figure 24.8 2n = 6 4n = 12 2n2n 4n4n Failure of cell division in a cell of a growing diploid plant produces a tetraploid branch. Gametes produced by flowers on this branch will be diploid. If offspring are viable and fertile, it is a new biological species. Sympatric speciation

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An allopolyploid Is an individual with > two chromosome sets, derived from different species Meiotic error; chromosome number not reduced from 2n to n Unreduced gamete with 4 chromosomes Hybrid with 7 chromosomes Unreduced gamete with 7 chromosomes Viable fertile hybrid Normal gamete n = 3 Normal gamete n = 3 Species A 2n = 4 Species B 2n = 6 2n = 10 Sympatric speciation Figure 24.9

33. Polyploidy is especially common in plants

34. From Micro- to Macro- Evolution Microevolution – Population and species-level evolution, including speciation Macroevolution – Speciation and all broader-scale evolutionary patterns and processes

35. AnagenesisCladogenesis Sufficient micro- evolutionary changes may occur that the earlier population is considered a separate species from the later population time Branching evolution occurs as speciation events accumulate. The formation of each new branch is a macroevolutionary event. Figure 24.2

36. AnagenesisCladogenesis Sufficient micro- evolutionary changes may occur that the earlier population is considered a separate species from the later population time Branching evolution occurs as speciation events accumulate The formation of each new branch is a macroevolutionary event Broad patterns across the resulting tree are also within the scope of macroevolution Figure 24.2

37. Adaptive Radiation One species gives rise to many others in a geologically short period of time E.g., Darwin’s finches Islands are good places to find adaptive radiations

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings E.g., Hawaiian silverswords Figure 24.12 Adaptive Radiation

39. Gradualism Punctuated Equilibrium Tempo of Evolution time Figure 24.13

40. Gradualism Punctuated Equilibrium Tempo of Evolution time Figure 24.13

41. Evolutionary Novelties Evolutionary novelties usually arise as modifications of existing traits Figure 24.14

42. Evolutionary Development (Evo-Devo) Slight alterations in development can have profound effects on adults Heterochrony = change in the rate or timing of development, relative to an ancestor E.g., paedomorphosis = heterochronic retention of juvenile structures in adulthood

43. Evolutionary Development (Evo-Devo) Slight alterations in development can have profound effects on adults Heterotopy = change in the physical position of a trait during development, relative to an ancestor E.g., feathers from one part of a bird’s body may become expressed on another part

44. Evolutionary Development (Evo-Devo) Allometric growth = relative growth rates of different body parts within a species during development

45. Evolutionary Development (Evo-Devo) Allometric growth = relative growth rates of different body parts within a species during development E.g., allometric growth in horned scarab beetles; certain clusters of cells grow faster than others

46. Evolutionary Development (Evo-Devo)

47. Phanaeus imperator Evolutionary Development (Evo-Devo)

48. Evolution is not “goal oriented” Evolution is a genetic response to the interaction between the individuals of a population and their current environment (which includes other individuals) Natural selection can only act on the phenotypic variation present, and selection can only cause evolutionary change if phenotypic variation results (at least in part) from genetic variation

49. Evolution is not “goal oriented” Therefore, even if female tigers in a population would prefer blue males, blue tigers will never evolve if the population lacks variation that includes blue fur He’s not blue, but he’s better than nothing! YES! But he exists only in my dreams.