Presentation is loading. Please wait.

Presentation is loading. Please wait.

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

Similar presentations


Presentation on theme: "Species and Speciation I. Species Concepts II. Recognizing Species A. Morphology B. Genetic Analysis C. Hybrid Analyses."— Presentation transcript:

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 BC

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 Hybrid Hybrid Backcross??

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 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. AABBx aabb F1all A-B- phenotype F2A-B- = 9/16 A-bb = 3/16 aaB- = 3/16 aabb = 1/ ~ 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 PNAS. Desmognathus ochrophaeus in western NC 1. correlation between geographic distance and genetic distance

42 Tilley et al 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 A1A1 B1B1 A 1 A 1 B 2 B 2 works A 2 A 2 B 1 B 1 works A 2 A 2 B 2 B 2 works A 1 A 1 B 1 B 1 lethal

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 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 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 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 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, mhrFemale D. melanogaster: lhr, m-mhr(X) s-lhr/lhr, m-mhr(X) = INVIABLE SONS

51 B. Hybrid Incompatibility D. melanogaster and D. simulans SYSTEM: (s-lhr dominant) D. sim = s-lhr, hmr (X) x D. mel = lhr, m-hmr (X) SONS GET : s-lhr/lhr, m-hmr/Y (only X).... INVIABLE

52 B. Hybrid Incompatibility D. melanogaster and D. simulans SYSTEM: D. sim = s-lhr, hmr (X) x D. mel = lhr, m-hmr (X) SONS GET : s-lhr/lhr, m-hmr (only X).... INVIABLE (w)D. sim = lhr/s-lhr, hmr (X) x D. mel = lhr, m-hmr (X) 1/2 SONS GET lhr/lhr, m-hmr (ONLY X) = VIABLE

53 B. Hybrid Incompatibility D. melanogaster and D. simulans SYSTEM: D. sim = s-lhr, hmr (X) x D. mel = lhr, m-hmr (X) SONS GET : s-lhr/lhr, m-hmr (only X).... INVIABLE (w)D. sim = lhr/s-lhr, hmr (X) x D. mel = lhr, m-hmr (X) 1/2 SONS GET lhr/lhr, m-hmr (ONLY X) = VIABLE D. sim = s-lhr, hmr (X) x (a) D. mel = lhr, m-hmr(X)/hmr (X) 1/2 SONS GET: s-lhr/lhr, hmr (only X) = VIABLE

54 B. Hybrid Incompatibility D. melanogaster and D. simulans SYSTEM: (s-lhr dominant) Ancestor: lhr, mhr D. simulans: s-lhr, mhrD. melanogaster: lhr, m-mhr s-lhr, m-mhr = INVIABLE

55 B. Hybrid Incompatibility D. melanogaster and D. simulans Brideau et al Science 314: isolated location of lhr gene. - put NORMAL D. simulans gene into D. melanogaster. - mated these D. melanogaster with Watanabe's mutant strain of D. simulans. - IF these two genes are partners, then 3/4 hybrids should die. (w) D. sim = lhr/s-lhr, hmr (X) x (b)D. mel = s-lhr/lhr, m-hmr (X) (doesn't die....) 1/4 SONS GET : lhr/lhr, m-hmr (only X).... VIABLE 3/4 get some other combination including s-lhr and m-hmr.. INVIABLE

56 Speciation I. Modes II. Mechanisms A. Progressive Genomic Incompatibility B. Hybrid Incompatibility C. Differential Selection

57 C. Differential Selection - Assumed to be primary, but few studies documenting that reproductive isolation of phenotypes correlates with fitness differential in different environments. Rundle et al. (2000). Science 287:306.

58 C. Differential Selection - Assumed to be primary, but few studies documenting that reproductive isolation of phenotypes correlates with fitness differential in different environments. Rundle et al. (2000). Science 287:306. Sticklebacks colonizing lakes...PHYLOGENY: benthic limnetic

59 C. Differential Selection - Assumed to be primary, but few studies documenting that reproductive isolation of phenotypes correlates with fitness differential in different environments. Rundle et al. (2000). Science 287:306. Mate selection correlates with ecotype, not with genetic relatedness.... example of parallel evolution, too.

60 Speciation I. Modes II. Mechanisms A. Progressive Genomic Incompatibility B. Hybrid Incompatibility C. Differential Selection D. Hybridization

61 D. Hybridization - When hybridization occurs, it show increase gene flow between populations. How are hybrids stabilized as a reproductively isolated group?

62 - adaptation to an extreme habitat Gompert et al Science 314: 1923.

63 - adaptation to an extreme habitat Gompert et al Science 314: Two species of small western butterflies have overlapping ranges.

64 - adaptation to an extreme habitat Gompert et al Science 314: Two cluster Three cluster Probabilities of assigning individuals from these populations to a particular dendrogram "cluster"

65 - adaptation to an extreme habitat Gompert et al Science 314: Two cluster Three cluster Probabilities of assigning individuals from these populations to a particular dendrogram "cluster" Are the alpine populations simply in hybrid zone, or are they reproductively isolated?

66 - adaptation to an extreme habitat Gompert et al Science 314: Two cluster Three cluster Probabilities of assigning individuals from these populations to a particular dendrogram "cluster" Are the alpine populations simply in hybrid zone, or are they reproductively isolated? They are fixed for several alleles, suggesting no gene flow.

67 - adaptation to an extreme habitat Gompert et al Science 314: Two cluster Three cluster Probabilities of assigning individuals from these populations to a particular dendrogram "cluster" Are the alpine populations simply in hybrid zone, or are they reproductively isolated? They are fixed for several alleles, suggesting no gene flow. - Also used coalescence to estimate time since a common ancestor within each 'species". The alpine populations had a more recent history (400,000 yrs) than either of the others ( my)

68 - adaptation to an extreme habitat Gompert et al Science 314: What maintains this genetic uniqueness?

69 - adaptation to an extreme habitat Gompert et al Science 314: What maintains this genetic uniqueness? Fidelity to Host Plant

70 - adaptation to an extreme habitat Gompert et al Science 314: What maintains this genetic uniqueness? Fidelity to Host Plant Also, their eggs don't stick to the leaf; they drop off into litter. This may be adaptive, as winds blow leaves a long way from original plant at high elevations. The host plant is a perennial, so dropping into the leaf litter keeps it close to host plant. Other species, even if they used the plant, would have eggs dispersed from the host plant. That's bad for butterflies, 'cuz caterpillars don't disperse too far...

71 D. Hybridization - When hybridization occurs, it show increase gene flow between populations. How are hybrids stabilized as a reproductively isolated group? - adaptation to extreme habitat - sexual selection

72 Mavarez et al Nature 441:868

73 X BACKCROSS

74 Offspring of H. heurippa x backcross Offspring of backcross x wild H. heurippa. B and Br loci are linked, so no recombinant types (white).

75 H. melH. heurH. cyn H. mel H. heur H. cyn Mating probabilities in no-choice experiments: strong Positive Assortative Mating Male female

76 Mate Pairing in Tetrads: strong Positive Assortative Mating

77 Speciation I. Modes II. Mechanisms A. Progressive Genomic Incompatibility B. Hybrid Incompatibility C. Differential Selection D. Hybridization Several ways that new gene combinations can form and become stabilized.


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

Similar presentations


Ads by Google