1. 1 Lecture #3 – Origin of Species Cartoon – gentleman and ape

2. 2 Key Concepts: Species concepts Development of reproductive isolation Patterns of speciation Macroevolution Human evolution Evolution continues…..

3. 3 specie “Species” is both singular and plural My pet peeve is….

4. 4 Diagram – variation in beaks between species Major Species Concepts Biological Morphological Phylogenetic

5. 5 Image – Sarracenia flava Image – Sarracenia rubra Biological species – the basic standard for separating species (Ernst Mayr, 1942) Species are defined by natural reproductive isolation  Individuals that can produce successful offspring are considered the same species ≠

6. 6 Critical Thinking Biological species are defined by natural reproductive isolation  Individuals that can produce successful offspring are considered the same species Definition doesn't always work – why not???

7. 7 Critical Thinking Biological species are defined by natural reproductive isolation  Individuals that can produce successful offspring are considered the same species Definition doesn't always work

8. 8 Image – Hymenocallis floridana Image – Hymenocallis coronaria Morphological species – the first way to separate species (Linnaeus, ~1750 & others) Species are defined by differences in form  Individuals with the same morphology and/or anatomy are considered the same species ≠

9. 9 Critical Thinking Morphological species are defined by differences in form  Individuals with the same morphology and/or anatomy are considered the same species Definition doesn't always work – why not???

10. 10 Critical Thinking Morphological species are defined by differences in form  Individuals with the same morphology and/or anatomy are considered the same species Definition doesn't always work

11. 11 Phylogenetic species – the new standard for separating species??? Species are defined based on evolutionary history  Species defined by the smallest monophyletic group in an evolutionary tree  Monophyletic = lineage is derived from a common ancestor Definition doesn't always work  Don’t have good phylogenies for all species or groups  Also, imperfect agreement on interpretations

12. 12 Development And Maintenance Of Reproductive Isolation: the essence of speciation What constitutes a barrier to reproduction? How do reproductive barriers develop? It is generally accepted that natural reproductive isolation defines and preserves separate species in sexually reproducing organisms

13. 13 Image – blue-footed boobies mating behavior Pre-zygotic Barriers Remember, the zygote is the fertilized egg cell  The first cell of the new offspring Pre-zygotic barriers prevent the formation of the zygote Natural, evolved incompatibilities prevent successful fertilization  Habitat isolation  Behavioral isolation  Temporal isolation  Structural isolation  Chemical isolation

14. 14 Critical Thinking Natural, evolved incompatibilities prevent successful fertilization Think of some examples of:  Habitat isolation  Behavioral isolation  Temporal isolation  Structural isolation  Chemical isolation

15. 15 Critical Thinking Habitat isolation Behavioral isolation Temporal isolation Structural isolation Chemical isolation

16. 16 Post-zygotic Barriers Post-zygotic barriers prevent successful development of offspring  Hybrids don’t develop properly  Hybrids don’t reach sexual maturity  Hybrids don’t produce viable gametes  Hybrid lineages fail over time Natural genetic incompatibilities prevent successful long-term reproduction Horse x Donkey = robust but sterile Mule

17. 17 Critical Thinking a.its ability to reproduce. b.how long it lives. c.the number of mates it attracts. d.the number of its offspring that survive to reproduce. e.its physical strength. The Darwinian fitness of an individual is measured by

18. 18 Critical Thinking a.its ability to reproduce. b.how long it lives. c.the number of mates it attracts. d.the number of its offspring that survive to reproduce. e.its physical strength. The Darwinian fitness of an individual is measured by

19. 19 Diagram – different species of fish in separated ponds Patterns of Speciation Barriers result from separations that persist long enough that eventually new species have developed

20. 20 Patterns of Speciation Pattern depends on the mechanism of gene flow interruption  Allopatric speciation occurs when populations are separated by a geographical barrier  Sympatric speciation occurs in the absence of a geographic barrier

21. 21 Critical Thinking Allopatric speciation occurs when populations are separated by a geographical barrier Such as???? How could such barriers form???

22. 22 Critical Thinking Allopatric speciation occurs when populations are separated by a geographical barrier How could such barriers form???

23. 23 Critical Thinking Allopatric speciation occurs when populations are separated by a geographical barrier How could such barriers form???

24. 24 Critical Thinking

25. 25 Allopatric Speciation Once populations are physically isolated, speciation may occur due to all the evolutionary processes we talked about earlier  Selection  Drift  Selective mating  Mutation

26. 26 Critical Thinking What if the isolated population is small??? What if the isolated population is from edge of the range of the original population???

27. 27 Critical Thinking What if the isolated population is small??? What if the isolated population is from edge of the range of the original population???

28. 28 Critical Thinking What if the isolated population is small??? What if the isolated population is from edge of the range of the original population???

29. Allopatric Speciation due to geographic separation 29 Images – different species of chipmunk on either side of the Grand Canyon Plants???? Birds????

30. 30 Diagram – sympatric  allopatric  either sympatric again or not, as a population separates around a mountain range and then re-unites Speciation may, or may not, occur…

31. 31 Diagram – sympatric speciation in a forest environment Sympatric Speciation Occurs when a population becomes reproductively isolated without geographic barriers  Mutations or selection pressures that lead to changes in behavior, habitat, food source, phenology….  Errors in meiosis that lead to polyploidy (some plants can be self- fertile, vegetative reproduction)  Hybrids that develop into fertile populations through vegetative reproduction or multiple events (mostly plants)

32. 32 Diagram – meiosis errors Sympatric Speciation Occurs when a population becomes reproductively isolated without geographic barriers  Mutations or selection pressures that lead to changes in behavior, habitat, food source, phenology….  Errors in meiosis that lead to polyploidy (some plants can be self- fertile, vegetative reproduction)  Hybrids that develop into fertile populations through vegetative reproduction or multiple events (mostly plants)

33. Polyploidy – one mechanism for sympatric speciation 33 Diagram – errors in meiosis can lead to polyploids Some plants can self-pollinate, or vegetative reproduction can produce multiple fertile individuals

34. 34 Sympatric Speciation Occurs when a population becomes reproductively isolated without geographic barriers  Mutations or selection pressures that lead to changes in behavior, habitat, food source, phenology….  Errors in meiosis that lead to polyploidy (some plants can be self-fertile, vegetative reproduction)  Hybrids that develop into fertile populations through vegetative reproduction or multiple events (mostly plants) Image showing hybrid asters

35. 35 Speciation is NOT a Given Must have an interruption to gene flow PLUS Must have enough change in the separated populations to produce a barrier to reproduction

36. 36 Endemic Species and Adaptive Radiation Endemic species = restricted in distribution to a particular place, generally because they evolved in place  Volcanic island chains often contain many endemic species  No biota until they were colonized by a few individuals (founder effect) These small populations then evolved into new species  Allopatric speciation due to the geographic barrier from the founder effect But also……

37. 37 Endemic Species and Adaptive Radiation Many new species develop that are adapted to the diverse new habitats found in such islands  Sympatric speciation  No geographic barriers  Adaptive radiation into new habitats Diagram showing adaptive radiation

38. 38 Diagrams – adaptive radiation in birds Adaptive Radiation Galapagos finches and Hawaiian honeycreepers

39. 39 Diagram – diversification of mammals after extinction of the dinosaurs Diagram – mass extinctions over the past 2.5 billion years Adaptive Radiation is a common theme – both between and within lineages Mammals Mass Extinction Events

40. 40 Critical Thinking Humans have initiated a mass extinction event Will life cease to exist on the planet??? Can we destroy the planet???

41. 41 Critical Thinking Humans have initiated a mass extinction event Will life cease to exist on the planet??? Can we destroy the planet???

42. 42 Critical Thinking Humans have initiated a mass extinction event Will life cease to exist on the planet??? Can we destroy the planet???

43. 43 Speciation is a Constant When migration, isolation or other selection pressures force divergence, reproductive isolation can eventually lead to speciation  Speciation might be gradual or abrupt (punctuated equilibrium)  Transitions (either gradual or abrupt) may or may not be captured in the fossil record

44. 44 Macroevolution: larger-scale changes in organisms Also contributes to speciation Small, population-scale changes can accumulate Exaptations – traits can be co-opted  Feathers for thermoregulation  feathers for flight Large phenotypic changes can result from small changes in regulatory genes  Control over the timing and length of developmental events, or the spatial organization of body parts

45. 45 Diagram – phylogeny of the modern horse Critical Thinking Was the evolution of the modern horse a series of directed events ????

46. 46 Critical Thinking Was the evolution of the modern horse a series of directed events???

47. 47 Selection is a series of gates!!!

48. 48 A Preview of the Taxonomic Hierarchy: this is how we classify diversity Taxonomic CategoryExample (taxon) DomainEukarya = all eukaryotic organisms KingdomPlantae, also Metaphyta = all plants Division (phylum)Magnoliophyta = all angiosperms ClassLiliopsida = all monocots OrderAsparagales = related families (Orchidaceae, Iridaceae, etc) FamilyOrchidaceae = related genera (Platanthera, Spiranthes, etc) GenusPlatanthera = related species (P. ciliaris, P. integra, etc) Specific name/epithetciliaris = one species

49. 49 Images – the yellow fringed orchid Platanthera ciliaris

50. 50 Humans can also be classified! Domain – eukarya Kingdom – animal Phylum – chordates  Sub-phylum – vertebrates Class – mammals Order – primates Family – hominoids Genus – Homo Specific epithet – sapiens Image of human fossil

51. 51 Phyla in the Animal Kingdom: Chordates This and next 6 slides show the phylogenetic placement of humans in the animal kingdom

52. 52 Sub-phyla in the Chordate Phylum: Vertebrates Sub-phylum

53. 53 Classes in the Vertebrate Sub- phylum: Mammals

54. 54 Close-up: Classes in the Vertebrate Sub-phylum

55. 55 Orders in the Mammal Class: Primates

56. 56 Families in the Primate Order: Hominoids – a monotypic family

57. 57 Some key steps in the evolution of primates – note that our last common ancestor with other modern primates was 6 to 10 MILLION years ago Loss of dinosaurs, Rise of mammals Diagram showing the different orders of primates

58. 58 Critical Thinking Is your uncle a monkey??? Cartoon showing gentleman and ape

59. 59 Critical Thinking Is your uncle a monkey??? Diagram showing phylogenetic relationships between primates

60. 60

61. 61 Diagram – phylogeny of humans Two key steps – bi-pedalism and large brain

62. 62 Critical Thinking Why is bi-pedalism so important?

63. 63 Critical Thinking Why is bi-pedalism so important?

64. 64 Images – human fossil and fossil footprints

65. 65 Critical Thinking Why is a large brain so important?

66. 66 Critical Thinking Why is a large brain so important?

67. 67 The fossil record shows changes in our species over time The path of human evolution is not ladder- like We are currently a mono-specific family, but…. Human phylogeny reveals many extinct lineages  We are animals  We are subject to natural selection  There is a record!

68. 68 All but one lineage of hominids are extinct Diagram – phylogeny of humans

69. 69 Diagram – multi-regional vs. “out of Africa” hypotheses for human migration patterns; same diagram on following 2 slides Out of Africa – Human Migration

70. 70 Critical Thinking How would you test these alternate hypotheses???

71. 71 Critical Thinking

72. 72 Evolution is a Constant Constant supply of genetic variation + constant application of selection pressures  All species are in some degree of flux New species are constantly diverging  ….and going extinct At any given time, we are just looking at a cross section of the process  A slice through the crown of a multi- dimensional tree Evolution is NOT finished!

73. 73 ….as the tree grows, so grows the tree of life…

74. 74 ….as the tree grows, so grows the tree of life… Species concepts Development of reproductive isolation Patterns of speciation Macroevolution Human evolution Evolution continues….. Key Concepts: Questions???

75. Hands On We’ll be starting with plants next time Bring in samples of plants to examine microscopically and macroscopically Anything that interests you – from nature, your kitchen, garden….. Parts or whole plants Save reproductive parts for later in the week 75