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Slide #1. Speciation from Mosquitoes to Humans: Chromosomal Rearrangements and Genic Diversification Slide #2. Models of Chromosomal Speciation Slide #3. Crossing over in a heterozygote for a paracentric inversion. Slide #4. Crossing over in a heterozygote for a pericentric inversion. Slide #5. Models of Chromosomal Speciation Slide #6. From J. Hey, 2003. Slide #7. The chromosomes from human, chimpanzee, gorilla, and orangutan; left to right. Slide #8. Rate of protein evolution in human chimpanzee divergence (A. N.H. Barton, 2003). Slide #9. Distribution of KA/KS in colinear and rearranged chromosomes Slide #10. KA/KS <BR> <BR> Rearranged chromosomes 0.84 <BR> Collinear chromosomes 0.37 Slide #11. “Taken at face value, this suggests that interbreeding or hybridization has been going on for up to half the time of divergence between the two lineages (see the figure).” Slide #12. <BR>Chromosomal rearrangements triggered the separation <BR>of humans from the great apes by providing a barrier to <BR>gene flow in rearranged chromosomes. Gene flow <BR>continued for genes on colinear chromosomes. <BR>(Riesberg and Livingstone, 2003.) <BR> Slide #13. Slide 13 Slide #14. Gorilla Slide #15. Slide 15 Slide #16. J. Lu, W.-H. Li, and C.-I. Wu, Science 302: 988b, 2003. Slide #17. Genomic DNA Sequence Divergence between Humans and Chimpanzees <BR> Slide #18. Synonymous and Nonsynonymous Divergences between Humans and Chimpanzees Slide #19. Figure 2. Average fold change (FC) values of collinear (squares) and rearranged (diamonds) chromosomes between humans and chimpanzees in cortical samples. The mean FC values and two standard errors (SEs) for each individual chromosome are shown. From Marquès-Bonet et al., Trends Genet. 20: 524-529, 2004. Slide #20. Distribution of recent and fossil orangutan. Slide #21. Eight races of orangutans in northwestern Borneo. B = Simia satyrus batangtuensis; D = S. s. dadappensis; G = S. s. genepaiensis; R = S. s. rantaiensis; S = S. s. skalauensis; T = S. s. tuakensis; W = S. s. Wallacei; L = S. s. landakkensis. Slide #22. The chromosomes of human and orangutan. <BR>B, Borneo; S, Sumatra Slide #23. Pericentric inversion differentiating human (chromosome 3) from orangutan (chromosome 2). Slide #24. Pericentric inversion of chromosome 2 distinguishing Bornean and Sumatran orangutans. Slide #25. Double inversion of chromosome 9, found in Bornean as well as in Sumatran orangutans. Slide #26. Variant chromosomes 14 and 22 in orangutans. Slide #27. Phylogeny of three Drosophila taxa. <BR>(After Brown et al., Evolution 58: 1856-1860, 2004.) Slide #28. Virtually all sterility factors between D.p. pseudoobscura and D. persimilis are associated with three inverted chromosome regions, whereas sterility between D.p. bogotana and D. persimilis factors are present in the collinear regions. <BR> <BR>(After Brown et al., Evolution 58: 1856-1860, 2004.) Slide #29. Cytological location of sequenced loci. Asterisks indicate regions strongly (**) or weakly (*) associated with isolation mechanisms between D. pseudoobscura and D. persimilis. (Machado et al. Mol. Biol. Evol. 19: 472-488, 2002.) Slide #30. Sequence variation in 50 inbred lines at 11 loci suggests that most gene flow between D. pseudoobscura and D. persimilis is not recent. <BR> <BR>There is less evidence of gene flow between D. pseudoobscura and D. p. bogotana. <BR> <BR>There is a good correspondence between the genomic regions associated with reproductive isolation and the regions that show little or no evidence of gene flow. <BR> <BR>(After Machado et al., Mol. Biol. Evol. 19: 472-488, 2002.) Slide #31. Annual cases worldwide between 300 and 500 million. Severe cases can result in death. Slide #32. Slide 32 Slide #33. Malaria Transmission in Africa Slide #34. Vector significance of African Anopheles Slide #35. (After M. Coluzzi et al., Science 298: 1415-1418, 2002.) Slide #36. The phylogenetic relationships among the seven described species of the Anopheles gambiae complex could be inferred from the distribution of fixed inversions. <BR> <BR>Ten inversions are fixed in different species in the complex. <BR> <BR>In An. gambiae from Mali, stable genetic differentiation was observed even in populations living in the same region, suggesting a process of incipient speciation. <BR> <BR>(After M. Coluzzi et al., Science 298: 1415-1418, 2002.) Slide #37. Slide 37 Slide #38. Slide 38 Slide #39. (Modified from Coluzzi, 1982.) Slide #40. Mitochondrial DNA sequences have introgressed between An. gambiae and An. arabiensis. <BR> <BR>Our results suggest that speciation is recent. <BR> <BR>Comparison of allopatric and sympatric populations suggests locale -specific unidirectional introgression from An. arabiensis into An. gambiae. <BR> <BR>(After M.J. Donnelly et al., Heredity 92: 61-68, 2004.) Slide #41. Evidence from gene sequences points to broad scale genetic exchange of autosomal sequences between Anopheles gambiae and An. arabiensis, while there are fixed differences and considerably deeper divergence on the X [which has fixed inversions between the two species]. <BR> <BR>The acquisition of An gambiae sequences from the more arid-adapted An. arabiensis may have contributed to the spread and ecological dominance of this malaria vector. <BR> <BR>(After N.J. Besansky et al., PNAS 100: 10818-10823, 2003.) Slide #42. The End Slide #43. Slide 43 Slide #44. Effect of Chromosomal Rearrangements on the Proportion of Genes under Positive Selection Slide #45. From Marquès-Bonet et al., Trends Genet. 20: 524-529, 2004. Slide #46. Models of Chromosomal Speciation Slide #47. Models of Chromosomal Speciation Slide #48. Hybrid male sterility, hybrid inviability, and the hybrid male courtship dysfunction are associated with X-autosome interactions involving primarily inverted chromosome regions. <BR> <BR>The absence of isolating mechanisms being associated with autosomal regions suggests that they may not be caused by genes spread throughout the genome. <BR> <BR>Gene flow, via hybrids, between D pseudoobscura and D. persimilis may be possible at loci spread across much of the autosomes. <BR> <BR>(After Noor et al., Evolution 55: 512-521, 2001.) <BR> Slide #49. Phylogeny of three Drosophila taxa. <BR>(After Brown et al., Evolution 58: 1856-1860, 2004.)