1. 1 Lecture #3 – Origin of Species

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  Speciation often occurs as the gradual divergence of multiple populations  Fuzzy boundaries during divergence Also, can’t be used to classify extinct species

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  Some species have a lot of natural phenotypic variation But, the only way to classify extinct species and species that lack sexual reproduction  Also important in describing new species

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 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 – different ecological niches Behavioral isolation – changes in mating behaviors…. Temporal isolation – the timing of reproductive events Structural isolation – mutations that change morphology of reproductive structures Chemical isolation – gametes must be compatible, pollen must “match”

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 Such as rivers, canyons, mountains, oceans, glaciers….. How could such barriers form???

23. 23 Critical Thinking Allopatric speciation occurs when populations are separated by a geographical barrier Such as rivers, canyons, mountains, oceans, glaciers….. How could such barriers form??? Geological processes  Mountain building  River erosion  Glaciation  Tectonic events  Cave formation

24. 24 Critical Thinking Also…. Climate changes that cause large lakes to dry up or form smaller, isolated lakes Colonization events that separate a group from the rest of the population (founder effect)

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???  Speciation is likely to occur more rapidly  More genetic drift, less gene flow 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???  Speciation is likely to occur more rapidly  More genetic drift, less gene flow What if the isolated population is from edge of the range of the original population???  It may be even more likely to diverge  Probably already adapting to frontier or edge conditions  Also, probably more likely to migrate

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

30. 30 Diagram – sympatric  allopatric  either sympatric again or not. 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 (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 (mostly plants)  Hybrids that develop into fertile populations through vegetative reproduction (mostly plants)

33. 33 Diagram – errors in meiosis can lead to polyploids Polyploidy – one mechanism for sympatric speciation Some plants can be self-fertile, 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 (mostly plants)

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

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???  Highly unlikely  There will just be a new set of species Can we destroy the planet???

42. 42 Critical Thinking Humans have initiated a mass extinction event Will life cease to exist on the planet???  Highly unlikely  There will just be a new set of species Can we destroy the planet???  Highly unlikely  The earth has survived for at least 4 billion years!  Species come and go….

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 No, there are lots of lineages that are now extinct Evolution may look directed, but it’s not.... 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

51. 51 Diagram – from this slide to slide #65 – phylogenies of the animal kingdom, showing the classification of humans through the taxonomic hierarchy from the phyla to the families in the primate order Phyla in the Animal Kingdom:

52. 52 Phyla in the Animal Kingdom: Chordates

53. 53 Sub-phyla in the Chordate Phylum:

54. 54 Sub-phyla in the Chordate Phylum: Vertebrates Sub-phylum

55. 55 Classes in the Vertebrate Sub- phylum: Sub-phylum

56. 56 Classes in the Vertebrate Sub- phylum: Mammals Sub-phylum

57. 57 Close-up: Classes in the Vertebrate Sub-phylum

58. 58 Orders in the Mammal Class:

59. 59 Orders in the Mammal Class: Primates

60. 60 Families in the Primate Order:

61. 61 Families in the Primate Order: Hominoids

62. 62 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

63. 63 Critical Thinking Is your uncle a monkey???

64. 64 Critical Thinking Is your uncle a monkey??? Of course not!!! Humans are NOT evolved from monkeys!

65. 65 Monkeys, apes and humans share a common ancestor, but have followed different evolutionary pathways for > 6 million years!

66. 66 Diagram – phylogeny of humans, same diagram on slide #73 Two key steps – bi-pedalism and large brain

67. 67 Critical Thinking Why is bi-pedalism so important?

68. 68 Critical Thinking Why is bi-pedalism so important? Bipedalism frees up 2 limbs for long- distance walking, hunting, gathering, caring for offspring  Current evidence is that this divergence began 6-10mya  Complete conversion in hominids by about 2mya

69. 69 Images – human fossil and fossil footprints

70. 70 Critical Thinking Why is a large brain so important?

71. 71 Critical Thinking Why is a large brain so important? Large brain allows for complex thought, abstract reasoning, spirituality, creativity, language, complex tools  Most of the traits that we consider uniquely human…  Larger brain began emerging about 2mya, stable for about 200,000 years

72. 72 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!

73. 73 All but one lineage of hominids are extinct

74. 74 Diagram – multi-regional vs. “out of Africa” hypotheses for human migration patterns; same diagram on following 2 slides Out of Africa – Human Migration

75. 75 Critical Thinking How would you test these alternate hypotheses???

76. 76 Critical Thinking DNA evidence supports this pathway

77. 77 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!

78. 78 ….as the tree grows, so grows the tree of life…

79. 79 ….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???