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Slide #1. Slide 1 Slide #2. Local population <BR> Subspecies <BR> Monotypic species <BR> Polytypic species <BR> Superspecies <BR> Species group <BR> <BR>Mayr’s hierarchy of speciation and systematics (p.172, Mayr 1942) Slide #3. Local population <BR> Subspecies <BR> Monotypic species <BR> Polytypic species <BR> Superspecies <BR> Species group <BR> Slide #4. A static view of biogeography and phylogeny Slide #5. Slide 5 Slide #6. Slide 6 Slide #7. Stages 1 and 2: all species allopatric, many polytypic Slide #8. Stage 1: Three species of Tripneustes Slide #9. Stage 3: "illustrates the next step in the speciation process" Slide #10. L,V Slide #11. Stage 4: species so old that ‘the actual course which speciation has taken has become completely obscured.’ Slide #12. Stage 1&2 Allopatry and polytypic spp. <BR> Stage 3 Geographic introgession <BR> Stage 4 Older sympatric spp Slide #13. Phylogenies help with: Sister species <BR>Divergence date <BR>Order of divergence <BR>Cryptic species <BR>Scale of panmixis <BR> Slide #14. Since 1954 urchinologists have been busy: genera from Mayr 1954 with good molecular phylogenies: <BR>Eucidaris Stage 1 <BR>Tripneustes Stage 1 <BR>Lytechinus Stage 2 <BR>Echinometra Stage 3 <BR>Diadema Stage 3 <BR>Arbacia Stage 4 <BR>Not in Mayr 1954 <BR>Strongylocentrotus Stage 4 <BR>Heliocidaris Stage 4 Slide #15. Tr Slide #16. Tr Slide #17. L,V Slide #18. L,V Slide #19. Major predictions from 8 generic phylogenies: <BR>Genetic divergence increases stage to stage. <BR>Most polytypic species are in Stage 1. <BR>Sympatric species more divergent than allopatric Slide #20. Major prediction confirmed: MtDNA distance among sea urchins Slide #21. Stages 1+2 Stage 3 Stage 4 <BR> Slide #22. Stages 1+2 Stage 3 Stage 4 <BR> Slide #23. Stages 1+2 Stage 3 Stage 4 <BR> Slide #24. Stages 1+2 Stage 3 Stage 4 <BR> Slide #25. Stages 1+2 Stage 3 Stage 4 <BR> Slide #26. Tr Slide #27. Stages 1+2 Stage 3 Stage 4 <BR> Slide #28. Stages 1+2 Stage 3 Stage 4 <BR> Slide #29. Stages 1+2 Stage 3 Stage 4 <BR> Slide #30. Stages 1+2 Stage 3 Stage 4 <BR> Slide #31. Acrosome reacted sperm Slide #32. Fertilization is restricted to sperm of the right species (right photo). Sperm from the wrong species (left photo) do not fuse with eggs. Slide #33. Rapid evolution of bindin sequences is due to strong positive selection. Slide #34. L,V Slide #35. Bindin evolution in urchin genera <BR>Tripneustes Slow <BR>Lytechinus Slow, 1 exception <BR>Echinometra Rapid <BR>Diadema Slow <BR>Arbacia Slow <BR>Strongylocentrotus Rapid <BR>Heliocidaris Rapid Slide #36. Allopatric <BR> <BR>Sympatric Slide #37. Conclusions: Allopatry is the rule except where gamete recognition systems are evolving rapidy. Slide #38. Impact on Isolation Slide #39. Impact on hybrid sterility Slide #40. Step 1: Find hybrids "Boots to the ground" Requires hours days of snorkeling on <BR>coral reefs Slide #41. Poor fertilization by hybrids Slide #42. Possible molecular mechanism Slide #43. But hybrids beware Slide #44. A new bindin allele will succeed only if Slide #45. This should generate heterozygote superiority Slide #46. Probability of fertilization by heterozygote male Slide #47. Can coevolution of alleles drive allopatric divergence? Slide #48. Rapid bindin evolution creates reproductive isolation and reduces hybrid fitness Slide #49. Slide 49 Slide #50. Slide 50 Slide #51. The great animator