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Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology

Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis C. Hybrid Analyses. Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis C. Hybrid Analyses

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Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology

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  1. Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis C. Hybrid Analyses

  2. Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis C. Hybrid Analyses - Create hybrids and examine their fertility. Infertility may be due to: - Epistatic interactions between loci derived from different parents. Maybe species one has A1A1B1B1 and species 2 has A2A2B2B2, and maybe A1 and B1 don't work together. If one is a sex linked gene, then sterility might be sex-specific.

  3. Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis C. Hybrid Analyses - Create hybrids and examine their fertility. Infertility may be due to: - Epistatic interactions between loci derived from different parents. Maybe species one has A1A1B1B1 and species 2 has A2A2B2B2, and maybe A1 and B1 don't work together. If one is a sex linked gene, then sterility might be sex-specific. - Hybrids that receive different inversion chromosomes may have lower fitness because crossing over produces aneuploid gametes - with chromosomes that lack centromeres and are lost from the cell line.

  4. Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis C. Hybrid Analyses - Create hybrids and examine their fertility. Infertility may be due to: - Epistatic interactions between loci derived from different parents. Maybe species one has A1A1B1B1 and species 2 has A2A2B2B2, and maybe A1 and B1 don't work together. If one is a sex linked gene, then sterility might be sex-specific. - Hybrids that receive different inversion chromosomes may have lower fitness because crossing over produces aneuploid gametes - with chromosomes that lack centromeres and are lost from the cell line. - Hybrids receiving chromosomes from parents with different reciprocal translocations may not have neat homologous sets.

  5. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation

  6. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers

  7. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat)

  8. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation

  9. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation 3. Behavior Isolation - don't recognize one another as mates

  10. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation 3. Behavior Isolation - don't recognize one another as mates 4. Mechanical isolation - genitalia don't fit

  11. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation 3. Behavior Isolation - don't recognize one another as mates 4. Mechanical isolation - genitalia don't fit 5. Gametic Isolation - gametes transfered but sperm can't fertilize egg

  12. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation 3. Behavior Isolation - don't recognize one another as mates 4. Mechanical isolation - genitalia don't fit 5. Gametic Isolation - gametes transfered but sperm can't fertilize egg B. Post-Zygotic Isolation

  13. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation 3. Behavior Isolation - don't recognize one another as mates 4. Mechanical isolation - genitalia don't fit 5. Gametic Isolation - gametes transfered but sperm can't fertilize egg B. Post-Zygotic Isolation 1. Genomic Incompatibility - zygote dies

  14. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation 3. Behavior Isolation - don't recognize one another as mates 4. Mechanical isolation - genitalia don't fit 5. Gametic Isolation - gametes transfered but sperm can't fertilize egg B. Post-Zygotic Isolation 1. Genomic Incompatibility - zygote dies 2. Hybrid Inviability - F1 has lower survival

  15. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation 3. Behavior Isolation - don't recognize one another as mates 4. Mechanical isolation - genitalia don't fit 5. Gametic Isolation - gametes transfered but sperm can't fertilize egg B. Post-Zygotic Isolation 1. Genomic Incompatibility - zygote dies 2. Hybrid Inviability - F1 has lower survival 3. Hybrid Sterility - F1 has reduced reproductive success

  16. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation A. Pre-Zygotic Barriers 1. Geographic Isolation (large scale or habitat) 2. Temporal Isolation 3. Behavior Isolation - don't recognize one another as mates 4. Mechanical isolation - genitalia don't fit 5. Gametic Isolation - gametes transfered but sperm can't fertilize egg B. Post-Zygotic Isolation 1. Genomic Incompatibility - zygote dies 2. Hybrid Inviability - F1 has lower survival 3. Hybrid Sterility - F1 has reduced reproductive success 4. F2 breakdown - F1's survive but F2's have incompatible combo's of genes

  17. Species and Speciation I. Species Concepts II. Recognizing Species III. Making Species - Reproductive Isolation IV. Speciation

  18. Speciation Speciation is not a goal, or a selective product of adaptation. It is simply a consequence of genetic changes that occurred for other reasons (selection, drift, mutation, etc.).

  19. Speciation I. Modes:

  20. Speciation I. Modes: A. Allopatric: Divergence in geographically separate populations - Vicariance - range divided by new geographic feature A B C

  21. Speciation I. Modes: A. Allopatric: Divergence in geographically separate populations - Vicariance - range divided by new geographic feature - Peripatric - divergence of a small migrant population A B

  22. Speciation I. Modes: A. Allopatric: Divergence in geographically separate populations - Vicariance - range divided by new geographic feature - Peripatric - divergence of a small migrant population B. Parapatric - neighboring populations diverge, even with gene flow

  23. Speciation I. Modes: A. Allopatric: Divergence in geographically separate populations - Vicariance - range divided by new geographic feature - Peripatric - divergence of a small migrant population B. Parapatric - neighboring populations diverge, even with gene flow

  24. B. Parapatric - neighboring populations diverge, even with gene flow Hybrid Backcross?? Hybrid

  25. Speciation I. Modes: A. Allopatric: Divergence in geographically separate populations - Vicariance - range divided by new geographic feature - Peripatric - divergence of a small migrant population B. Parapatric - neighboring populations diverge, even with gene flow C. Sympatric: Divergence within a single population

  26. C. Sympatric: Divergence within a single population Maynard Smith (1966) - hypothesized this was possible if there was disruptive selection within a population - perhaps as a specialist herbivore/parasite colonized and adapted to a new host.

  27. C. Sympatric: Divergence within a single population Maynard Smith (1966) - hypothesized this was possible if there was disruptive selection within a population - perhaps as a specialist herbivore/parasite colonized and adapted to a new host. Example: Hawthorn/Apple Maggot Fly (Rhagoletis pomonella) Hawthorn maggot fly is a native species that breeds on Hawthorn (Crataegus sp.)

  28. C. Sympatric: Divergence within a single population Maynard Smith (1966) - hypothesized this was possible if there was disruptive selection within a population - perhaps as a specialist herbivore/parasite colonized and adapted to a new host. Example: Hawthorn/Apple Maggot Fly (Rhagoletis pomonella) Europeans brought apples to North America. They are in the same plant family (Rosaceae) as Hawthorn.

  29. C. Sympatric: Divergence within a single population Maynard Smith (1966) - hypothesized this was possible if there was disruptive selection within a population - perhaps as a specialist herbivore/parasite colonized and adapted to a new host. Example: Hawthorn/Apple Maggot Fly (Rhagoletis pomonella) Europeans brought apples to North America. They are in the same plant family (Rosaceae) as Hawthorn. In 1864, apple growers noticed infestation by Apple Maggot flies...which were actually just "hawthorn flies"...

  30. C. Sympatric: Divergence within a single population Maynard Smith (1966) - hypothesized this was possible if there was disruptive selection within a population - perhaps as a specialist herbivore/parasite colonized and adapted to a new host. Example: Hawthorn/Apple Maggot Fly (Rhagoletis pomonella) races breed on their own host plant, and have adapted to the different seasons of fruit ripening. Only a 4-6% hybridization rate. Temporal, not geographic, isolation.

  31. C. Sympatric: Divergence within a single population But can a generalist speciate sympatrically? Tauber and Tauber. 1977a and 1977b. Science. Two species of green lacewings - generalist insect predators Chrysopa downesi has one generation in early spring C. carnea breeds has three generations in summer

  32. C. Sympatric: Divergence within a single population But can a generalist speciate sympatrically? Tauber and Tauber. 1977a and 1977b. Science. Two species of green lacewings - generalist insect predators Chrysopa downesi has one generation in early spring, then diapause C. carnea breeds has three generations in summer, no diapause The differences are due to responses to photoperiod C. downesi stops reproducing and goes into diapause under long day length (summer), whereas C. carnea reproduces under long day length.

  33. C. Sympatric: Divergence within a single population But can a generalist speciate sympatrically? Tauber and Tauber. 1977a. Science 197:592. The species are completely interfertile in the lab: Did reciprocal matings: C. downesi x C. carea Reared F1 offspring under long day length (16L:8D). Found all F1 did not enter diapause (C. carnea photoperiod response is dominant).

  34. C. Sympatric: Divergence within a single population But can a generalist speciate sympatrically? Tauber and Tauber. 1977a. Science 197:592. Did F1 x F1 cross: Found 7% (~1/16) of F2 exhibited diapause at 16L:8D. This is consistent with a model of 2 independently assorting autosomal genes with complete dominance at each and an interactive effect. AABB x aabb F1 all A-B- phenotype F2 A-B- = 9/16 A-bb = 3/16 aaB- = 3/16 aabb = 1/16.... ~ 7% C. carnea photoperiod C. downesi photoperiod

  35. C. Sympatric: Divergence within a single population But can a generalist speciate sympatrically? Tauber and Tauber. 1977a. Science 197:592. F1 x C. downesi backcross had 3:1 ratio, as expected of model. AaBb x aabb AaBb = .25 Aabb = .25 aaBb = .25 aabb = .25 C. carnea photoperiod C. downesi photoperiod

  36. C. Sympatric: Divergence within a single population But can a generalist speciate sympatrically? Tauber and Tauber. 1977b. Science 197:1298. How did this temporal separation get established? C. downesi is dark green and prefers hemlock forests C. carnea is light green and prefers fields and meadows Difference governed by a single locus where dark is incompletely dominant.

  37. C. Sympatric: Divergence within a single population But can a generalist speciate sympatrically? Tauber and Tauber. 1977b. Science 197:1298. How did this temporal separation get established? C. downesi is dark green and prefers hemlock forests C. carnea is light green and prefers fields and meadows Difference governed by a single locus where dark is incompletely dominant. Hypothesize that selection for different morphs in different habitats created the stable dimorphism, reinforced by inbreeding within the habitats. intermediate heterozygote

  38. C. Sympatric: Divergence within a single population But can a generalist speciate sympatrically? Tauber and Tauber. 1977b. Science 197:1298. How did this temporal separation get established? C. downesi is dark green and prefers hemlock forests C. carnea is light green and prefers fields and meadows Difference governed by a single locus where dark is incompletely dominant. Hypothesize that selection for different morphs in different habitats created the stable dimorphism, reinforced by inbreeding within the habitats. Selection then favored early breeding in C. downesi, as that is when insects feeding on conifers are most abundant.

  39. Speciation I. Modes II. Mechanisms

  40. Speciation I. Modes II. Mechanisms A. Progressive Genomic Incompatibility

  41. Tilley et al. 1990. PNAS. Desmognathus ochrophaeus in western NC 1. correlation between geographic distance and genetic distance

  42. Tilley et al. 1990. PNAS. Desmognathus ochrophaeus in western NC 2. Placed sympatric and allopatric males and females (reciprocal mating design) together for an evening and examined the cloaca of female in the morning for presence of sperm packet. Calculated "Coefficient of Isolation": (sum of % of sympatric matings) - (sum of % of allopatric matings) 2 = total isolation by sexual selection 0 = no differentiation by sexual selection

  43. Speciation I. Modes II. Mechanisms A. Progressive Genomic Incompatibility B. Hybrid Incompatibility - Dobzhansky and Müller (1930's) Pairs of genes that work together diverge in different populations

  44. Speciation I. Modes II. Mechanisms A. Progressive Genomic Incompatibility B. Hybrid Incompatibility - Dobzhansky and Müller (1930's) Pairs of genes that work together diverge in different populations A1A1B1B1 lethal A1A1B2B2 works A1 A2A2B1B1 works A2A2B2B2 works B1

  45. B. Hybrid Incompatibility D. melanogaster and D. simulans

  46. B. Hybrid Incompatibility D. melanogaster and D. simulans Cross female D. mel. x male D. sim - no sons

  47. B. Hybrid Incompatibility D. melanogaster and D. simulans Cross female D. mel. x male D. sim - no sons - Watanabe - 1970 - isolated a mutant strain of D. simulans (w) that could make males with D. melanogaster....

  48. B. Hybrid Incompatibility D. melanogaster and D. simulans Cross female D. mel. x male D. sim - no sons - Watanabe - 1970 - isolated a mutant strain of D. simulans(w) that could make males with D. melanogaster.... - Hypothesized that this strain had a mutant gene partner that reestablished function with the D. melanogaster partner gene... called it "lethal hybrid rescue" (lhr).

  49. B. Hybrid Incompatibility D. melanogaster and D. simulans Cross female D. mel. x male D. sim - no sons - Watanabe - 1970 - isolated a mutant strain of D. simulans (w) that could make males with D. melanogaster.... - Hypothesized that this strain had a mutant gene partner that reestablished function with the D. melanogaster partner gene... called it "lethal hybrid rescue" (lhr). - Ashburner - 1980 - isolated a mutant strain of D. melanogaster (a) females that could breed with D. simulans males and produce sons...called it "hybrid male rescue" - hmr - X-linked

  50. B. Hybrid Incompatibility D. melanogaster and D. simulans SYSTEM: (s-lhr dominant) Ancestor: lhr, mhr Male D. simulans:s-lhr, mhr Female D. melanogaster: lhr, m-mhr(X) s-lhr/lhr, m-mhr(X) = INVIABLE SONS

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