Species and Speciation I. Species Concepts II. Recognizing Species

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

2. 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.).

3. Speciation I. Modes:

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

6. Almost all most recent divergence events date to 3 my, and separate species on either side of the isthmus

7. 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

8. Abert’s Squirrel Kaibab Squirrel Crossed grand canyon to the north during Ice Age and isolated.

9. 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

10. 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

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

12. 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

13. 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.

14. 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.)

15. 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.

16. 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"...

17. 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.

18. 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 and has three generations in summer

19. 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.

20. 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).

21. 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 additive 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

22. 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

23. 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.

24. 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

25. 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.

26. Speciation I. Modes II. Mechanisms

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

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

29. 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

30. 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

31. 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

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

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

34. 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....

35. 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).

36. 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

37. 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

38. 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

39. 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

40. 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

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

42. B. Hybrid Incompatibility D. melanogaster and D. simulans Brideau et al. 2006. Science 314: 1292-1295 - 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

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

44. 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.

45. 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: limnetic benthic limnetic benthic limnetic benthic

46. 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.

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

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

49. - adaptation to an extreme habitat Gompert et al. 2006. Science 314: 1923.

50. - adaptation to an extreme habitat Gompert et al. 2006. Science 314: 1923. Two species of small western butterflies have overlapping ranges.