Slide image
Slide #1. Speciation and cospeciation in the fig/fig wasp mutualism Slide #2. Acknowledgements <BR> <BR>Smithsonian Tropical Research Institute (STRI) Slide #3. Acknowledgements <BR> <BR>Smithsonian Tropical Research Institute (STRI) Dr. Allen Herre <BR>Dr. Drude Molbo <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR>U. of Arizona: Whitman Schofield <BR> Erica Hudson, Anshu Dhawan <BR> EEB <BR> Arizona Genomics Institute Slide #4. Figs (Ficus, Moraceae) Slide #5. Fig wasps (Agaonidae, <BR>Chalcidoidea) Slide #6. Slide 6 Slide #7. MODEL SYSTEM TO STUDY: <BR> <BR>Pollination mutualisms <BR> <BR>Coevolution <BR> <BR>Sex Allocation <BR> <BR>Kin selection (fighting and extreme agression) <BR> <BR>Evolution of Virulence Slide #8. Specious mutualism: <BR> <BR>Approx. 800 described species of figs worldwide. <BR>Dioecious and Monoecious breeding systems (50% each) <BR> <BR>One partner mediates gene flow of the other <BR> <BR>Pantropical distribution <BR> <BR>High Global and Local species diversity <BR> <BR>Large number of species occur sympatrically <BR> <BR>Species with large geographical ranges, and with large variation across species range Slide #9. How did all this species diversity generate? <BR> <BR>How does speciation occur in this system? <BR> <BR>Allopatric? Parapatric? Sympatric? <BR> <BR>Is cospeciation the prevalent pattern of divergence? <BR> <BR>Or is this system more complex than we thought? Slide #10. Overview of biology <BR> <BR>Historical Biogeography <BR> <BR>History of codivergence at a coarse taxonomic scale <BR> <BR>History of codivergence at finer taxonomic scales (Neotropics) <BR> <BR>Speciation and diversity-generating mechanisms in this system Slide #11. Syconium Slide #12. Figs are an important food source <BR>for many tropical frugivores Slide #13. Ficus glabrata Slide #14. Tetrapus sp. Slide #15. Fig wasps are small… Slide #16. Range in wasp size in two genera Slide #17. Receptive fig Slide #18. Receptive fig Slide #19. Receptive fig Slide #20. Receptive fig Slide #21. Receptive fig Slide #22. t 1 Slide #23. Pegoscapus estherae <BR> <BR> Pollinator Slide #24. Apocrypta sp. on F. sur <BR>(Photo: Simon van Noort) Slide #25. (Photos: J-Y Rasplus) Slide #26. Idarnes sp. <BR>External competitor Slide #27. 12S mt rDNA phylogeny Slide #28. 0.05 substitutions/site Slide #29. Historical Biogeography <BR>Clock Calibration <BR> Fossil Pegoscapus fig pollinator in amber (20-25 Myr) Slide #30. Historical Biogeography <BR> <BR>Clock Calibration <BR> <BR>Fossil fig pollinating wasp: <BR> <BR> Pegoscapus sp. from Dominican amber (20-25 My) <BR> <BR>Origin of Chalcids: 140-165 My <BR> <BR>Diptera-Hymenoptera divergence: 250-300 My <BR> <BR>Fast evolving lineages pruned from the tree <BR> <BR>Estimated rates (Tv, silent) are similar to those of Drosophila Slide #31. 0.05 substitutions/site Slide #32. 0.05 substitutions/site Slide #33. 0.05 substitutions/site Slide #34. 0.05 substitutions/site Slide #35. 0.05 substitutions/site Slide #36. 0.05 substitutions/site Slide #37. Current historical biogeographic hypothesis: <BR> <BR>-Mutualism established during Cretaceous <BR> <BR>-Divergence events and estimated times match currently accepted <BR>scenario for the breakup of Gondwana during late Cretaceous. <BR> <BR>-Divergence of Australian pollinators matches Paleocene <BR>separation of Australia from Antarctica-South America <BR> <BR>-Divergence of American Urostigma pollinators matches Eocene <BR>Separation of South America from Antarctica Slide #38. CODIVERGENCE Slide #39. PHARMACOSYCEA Slide #40. Evidence for coarse scale co-cladogenesis / co-adaptation <BR> <BR>Suggestive of fine scale co-speciation… <BR> <BR> However….that pattern can also be generated <BR> <BR> by less specific coevolution of related groups of wasps and related groups of figs Slide #41. PHARMACOSYCEA Slide #42. <BR> Major incongruencies suggest potential ancient host switches and breakdown of species-specific associations <BR> <BR> Matching of phylogenies and assumption of host <BR>specificity has been used to propose cospeciation <BR> <BR>But… <BR> <BR>Have we really tested the cospeciation hypothesis? <BR> <BR>Is cospeciation the right paradigm? Slide #43. Weiblen & Bush (2002) Slide #44. We are interested in understanding the basic evolutionary processes/mechanisms that generate patterns of phylogenetic congruence and incongruency. <BR> <BR>Sampling diverged lineages will not allow us to <BR>understand species-level processes <BR> <BR>We need to study divergence processes in closely <BR>related/sympatric fig taxa and their pollinators Slide #45. 0.05 substitutions/site Slide #46. Slide 46 Slide #47. Neotropical figs Total Panama canal <BR> <BR>Pharmacosycea Pharmacosycea 20 sp. 4 sp. <BR>(most basal group of figs) <BR> <BR>Urostigma Americana 120 sp. 14 sp. <BR> Slide #48. cDNA library resources from Neotropical taxa Slide #49. F.popenoei Slide #50. F.bullenei Slide #51. F.colubrinae Slide #52. General lack of congruency among fig and wasp phylogenies <BR> <BR>Gene trees from different fig genes are not congruent: <BR> <BR> Tpi vs G3pdh p = 0.08 <BR> Tpi vs ITS p = 0.31 <BR> ITS vs G3pdh p = 0.14 Slide #53. Reasons for the observed incongruency… <BR> <BR>1. Large effective population sizes of the figs leading to massive levels of shared ancestral polymorphism <BR> <BR> Slide #54. Figs have the highest documented distances for gene flow of any tropical plant Slide #55. Heterozygosity <BR> <BR>Ficus citrifolia 0.258 <BR>F. dugandii 0.235 <BR>F. nympheifolia 0.169 <BR>F. obtusifolia 0.231 <BR>F. perforata 0.227 <BR>F. pertusa 0.258 <BR>F. popenoei 0.223 <BR> <BR>Average 0.229* <BR> <BR>(*Among highest in flowering plants) Slide #56. Assuming neutrality, stepwise mutation model for electrophoretic variants, and ? between 10-7 and 10-9 <BR> <BR> Ne ? 7 x 105 to 7 x 107 (!) Slide #57. Reasons for the observed incongruency... <BR> <BR>1. Large effective population sizes of the figs leading to massive levels of shared ancestral polymorphisms <BR> <BR>2. Pollinator host switches and gene introgression across different fig species Slide #58. <BR> <BR>But if pollinating wasps are host-specific and there is only one wasp per fig species, how can gene flow occur across different fig species? <BR> <BR> Slide #59. There are <BR>two or more species <BR>of pollinators <BR>in one Ficus Slide #60. Frequency Slide #61. Wasp species within crops <BR>F. obtusifolia Slide #62. Three hybrid broods were found <BR>out of 454 broods Slide #63. Two pollinators <BR>to one fig species <BR>is not uncommon Slide #64. COI ML Slide #65. Neotropical "cryptic" pollinator species (Pegoscapus) <BR> <BR>Fig species Certain Potential <BR> (many crops) (few indiv.) <BR> <BR>F. bullenei 4 <BR>F. triangle 3 <BR>F. obtusifolia 2 1 <BR>F. popenoei 2 <BR>F. perforata 2 <BR> <BR>Shared pollinators: <BR> <BR>F. popenoei/ F. bullenei/ F. triangle <BR>F. perforata/F. colubrinae Slide #66. COI ML Slide #67. COI ML Slide #68. COI ML Slide #69. w17 Slide #70. Distances among Pegoscapus sp. haplotypes <BR> <BR> ID Closest Average <BR> <BR>COI mtDNA 4.2 % 7.4 % <BR> <BR>E3N24 Adh-2S 3.3 % 8.9 % <BR>E3C10 ASP3c 4.1 % 11.1 % <BR>E1C24 Fibrillin 3.9 % 15.9 % <BR>E3G14 ORFan 2.9 % 14.1 % <BR>E1G04 ORFan 2.0 % 5.5 % Slide #71. IMPLICATIONS FOR FIG GENETICS <BR> <BR>1. If two fig species share a pollinator species: <BR> <BR>There should be current gene flow among species <BR> <BR>2. If there has been a host switch by a pollinator: <BR> <BR>One may see evidence of past gene introgression <BR>(during host switch) <BR> <BR>All those processes can generate incongruent phylogenies <BR>and lead to maintenance of shared variation across fig <BR>species Slide #72. These findings suggest three complementary approaches <BR>to study codivergence in this mutualism: <BR> <BR>Continue comparing phylogenies… <BR> <BR>Test specific gene flow predictions/routes based on observed shared host associations and inferred host switches and using population genetic methods <BR> <BR>Conduct field studies to determine performance of wasps in <BR> shared hosts <BR> Slide #73. Comparison of combined Tpi-G3pdh (fig) vs. COI (wasp) phylogenies Slide #74. Focus on shared pollinators: <BR> <BR>F. popenoei (F4)/ F. bullenei (F15)/ F. triangle (F7) <BR> <BR>F. perforata (17)/F. colubrinae (F16) <BR> <BR> <BR>Fig genes: G3pdh <BR> Tpi <BR> P1E01 (Thioredoxin) <BR> C2E19 (ORFan) <BR> C3I14 (ORFan) Slide #75. Tpi Slide #76. Slide 76 Slide #77. Slide 77 Slide #78. sp. 1 Slide #79. sp. B Slide #80. Testing Isolation Model <BR> <BR>F. bullenei (F15) vs F. near trigonata (F7) <BR> <BR>5 loci <BR>p = 0.045 <BR> <BR> Slide #81. Divergence Slide #82. Slide 82 Slide #83. How does speciation happen in this system? <BR> <BR>1. Allopatric: Ramirez 1970, Janzen 1979 <BR> <BR> Unlikely: long distance gene flow (Nason et al, 1998) <BR> <BR>2. Sympatric by temporal isolation (flowering asynchrony): Kiester, Lande, Schemske (1984) <BR> <BR> Unlikely: no evidence of asynchrony <BR> <BR>3. "Pollinator generalization": Baker 1961 <BR> Slide #84. If multiple and sloppy pollinators are fundamental for generating diversity in this system then we want to understand <BR> <BR>- Geographic variation <BR> <BR> <BR> Slide #85. If multiple and sloppy pollinators are fundamental for generating diversity in this system then we want to understand <BR> <BR>- Geographic variation <BR> <BR>We also want to understand constraints imposed by <BR> <BR> Morphology: Ostiole shape <BR> Ovipositor length <BR> <BR> Physiology: Thermal regulation <BR> <BR> Chemistry: Similarities of volatile attractants <BR> Slide #86. Acknowledgements <BR> <BR>Smithsonian Tropical Research Institute (STRI) Dr. Allen Herre <BR>Dr. Drude Molbo <BR> <BR> <BR> <BR> <BR> <BR> <BR> <BR>U. of Arizona: Whitman Schofield <BR> Erica Hudson, Anshu Dhawan <BR> EEB <BR> Arizona Genomics Institute