Micro to Macro Evolution Birds have and continue to be important models of the speciation process 30 year insight into evolution and speciation in Darwin’s Finches Great Adaptive Radiation Focus on Changes in Bill Size in Relation to Competitors and Environment Variable, but distinct species where several co-occur Possible hybridization Character shifts History and Phylogeny • Common Ancestor, something like a grassquit • Warbler finch earliest split • Galapagos colonized then Cocos • Likely 23my—during cycles of Pleistocene glacial advance and retreat Random Drift after Colonization Micro-Evolution Natural Selection drives consistent change rather than random variation from drift Drought selected for large billed birds in 1977 who produced largebilled offspring in 1978 Competition Forces Larger Differences When large billed finches of different species colonize an island, medium-billed finches are selected to evolve smaller bills by a process known as Character Displacement Macro-EvolutionSpeciation A strong interplay between isolation, hybridization, natural selection, drive speciation which is confirmed or negated when populations come back into contact Reproductive Isolation Mate selection is assortative for bill size/shape and song which acts to reinforce “species boundaries” Mountains and Glaciers • Importance of reproductive isolating factors and allopatric speciation Glacial advances and retreats in American Redstarts (Colbeck et al. 2008) and White-throated Dippers (Hourlay et al. 2008) Andes Mountains and the diversification in Wedge-billed Woodcreepers (Mila et al. 2009) Mountains, Natural Selection along Gradients • Vicariant versus ecological factors • Allopatric versus parapatric speciation • Woodcreeper ranges to 1500m in Eucador, a steep and substantial environmental gradient • Measured morphology likely to respond to foraging, flight, and general climate (Bergmann’s rule that animals are larger in colder climates) Support for morphology responding to environment • Wing and tarsus respond to relevant environmental effects on flight and foraging • General increase in body size with elevation as Bergmann would have predicted. And Significant Genetic Variation attributed to Andes as Barrier 2 distinct clades on eastside suggest ancient split and secondary contact Differences consistent with amount that would accumulate with .83.2my of drift— Andes uplift was 3my Natural Selection Effects Change Despite Gene Flow On east side, where gene flow is substantial there are still differences among birds from different (but not the same) habitats This microevolution may lead to macroevolution The importance of lowland – foothill transition areas in Andes are highlighted. They are important sources of variation in a bird and hence important areas to conserve. Glaciation and Refuges • Many studies have shown that significant variation within a species is likely associated with past isolation in separate glacial refuges – 700,000 years of ebbs and expansions of glaciers every ~100,000 years • Pleistocene refuges – Single refuge • Species with narrow current range • Widespread species with limited migratory ability – Two or more • Species currently widely distributed across significant geographic barriers Colbeck et al. 2008 European Dippers show Complex Pattern Consistent with Multiple Refuges Hourlay et al. 2008 European Dippers show Complex Pattern Consistent with Multiple Refuges Strong Genetic Differences requiring a Minimum 4 mutation events to produce changes Amount of variation between groups suggests longest separation between Asian birds and others (~250000 years), long history (120000 years) of separation between east and west Europe, less (40-100000 years) between others Significant difference between populations of what we currently classify as a single subspecies (east and west Europe) Likely many refuges north Italy Sicily Balkans Ural Mountains (Russia) Hourlay et al. 2008 Redstarts Show A Different Pattern Widespread, but no difference east vs. west Strong difference between Newfoundland and continental (likely arose 40,000 – 2,000,000 years ago) Support for 1 large refuge (likely in SE US) and a second smaller one in Newfoundland So, all widespread continental birds were not affected in same way by glaciation during Pleistocene How Does Micro- become Macro-Evolution? • Natural Selection, Sexual Selection, maybe chance while isolated prevents interbreeding when reconnected – Greenish Warbler (Irwin et al. 2001), sexual selection and cultural evolution of song types preclude interbreeding at either end of ring (blue vs. red) References • Colbeck, G. J., Gibbs, H. L., Marra, P. P., Hobson, K., and M. S. Webster. 2008. Phylogeography of a widespread North American migratory songbird (Setophaga ruticilla). Journal of Heredity 99:453-463. • Grant, P. R. and B. R. Grant. 2008. How and Why Species Multiply. Princeton Univ. Press. • Hourlay, F., Libois, R.Damico, F., Sara, M., O’Halloran, J, and J. R. Michaux. 2008. Evidence of a highly complex phylogenetic structure on a specialist river bird species, the dipper (Cinclus cinclus). Molecular Phylogenetics and Evolution 49:435-444. • Irwin, D. E., Bensch, S., and T. D. Price. 2001. Speciation in a ring. Nature 409:333-337. • Mila, B., Wayne, R. K., Fitze, P. and T. B. Smith. 2009. Divergence with gene flow and fine-scale phylogeographical structure in the wedge-billed woodcreeper, Glyphorynchus spirurus, a Neotropical rainforest bird. Molecular Ecology 18:2979-2995.