Slide 1The Structure of Evolutionary TheorySlide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10In PracticeSlide 12Slide 13Slide 14Sympatric speciationSympatric speciationAllopatric speciationAllopatric speciationAllopatric speciationAllopatric speciationParapatric speciationParapatric speciationParapatric speciationSlide 24Slide 25Demonstrating sympatric speciationSympatric Speciation Example The Palms of Lord Howe IslandSpecies must be sympatricSpecies must be sympatricSpecies must be sister taxaSpecies must be reproductively isolatedEarlier allopatric phase unlikelyEarlier allopatric phase unlikely: Age of palms vs islandDemonstrating sympatric speciationSlide 35Speciation mechanismsSpeciation mechanismsCauses of reproductive isolationPunctuated EquilibriumPunctuated Equilibrium vs Phyletic GradualismPunctuated Equilibrium and Speciation(How) Can we test punctuated equilibrium?Example of Phyletic GradualismGradual increase in rib numberOutstanding Questions Relating to Punctuated EquilibriumOutstanding Questions Relating to Punctuated EquilibriumOutstanding Questions Relating to Punctuated EquilibriumFor ThoughtLecture 13Speciation and Punctuated EquilibriumThe Structure of Evolutionary Theory•Agency•Efficacy•Scope – Does natural selection extrapolate to explain all of macroevolution?https://www.grc.org/programs.aspx?id=16902What is a species?What is a species?~8.7 million specieshttp://www.sciencedaily.com/releases/2011/08/110823180459.htmSpecies definitionsMore on definitions: http://scienceblogs.com/evolvingthoughts/2006/10/01/a-list-of-26-species-concepts/Phenetic: Phenotypic similarityBiological (BSC): Reproductive isolation (Ernst Mayr)Ecological: Species sort into distinct niches (Van Valen)Phylogenetic: OTUsPluralistic: No single concept applies to all speciesPornographic: “I know it when I see it”I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description ["hard-core pornography"], and perhaps I could never succeed in intelligibly doing so. But I know it when I see it, and the motion picture involved in this case is not that.[4]http://en.wikipedia.org/wiki/I_know_it_when_I_see_itUS Supreme Court Justice Potter Stewart (1964)In PracticeFundamental biological unitLinnean binomial nomenclature:Homo sapiens, Gallus gallus, Gorilla gorilla, Hyena hyena, Lemmus lemmus, Cannabis sativa,Escherichia coli, Saccharomyces cerevisiaeTaxonomists define species by easily identifiable morphological characters that are “fixed differences”Carl von Linné aka Carolus Linnaeus (1707-1778)http://openi.nlm.nih.gov/detailedresult.php?img=2553801_1471-2148-8-249-1&req=4http://evolution.berkeley.edu/evosite/evo101/VC1aModesSpeciation.shtmlGeographical modes of speciationSympatric speciationNo geographical isolationSympatric speciationNo geographical isolationAllopatric speciationGeographical isolationAllopatric speciationGeographical isolationAllopatric speciationGeographical isolationAllopatric speciationGeographical isolationParapatric speciationHybrid zoneParapatric speciationHybrid zoneParapatric speciationHybrid zoneTopopatric speciation?http://www.nature.com/nature/journal/v460/n7253/abs/nature08168.htmlAllopatric speciation?Peter and Rosemary GrantDemonstrating sympatric speciation•Species must be sympatric•Species must be sister taxa•Species must be reproductively isolated•Earlier allopatric phase must be unlikelySympatric Speciation ExampleThe Palms of Lord Howe IslandSpecies must be sympatricThatch Palm Curly PalmSpecies must be sympatricThatch Palm = blackCurly Palm = greySpecies must be sister taxaSpecies must be reproductively isolatedThatch PalmCurly PalmEarlier allopatric phase unlikelyEarlier allopatric phase unlikely:Age of palms vs islandPalms: 1.92 +/- 0.53 MYIsland: 6.9 MYDemonstrating sympatric speciation•Species must be sympatric•Species must be sister taxa•Species must be reproductively isolated•Earlier allopatric phase must be unlikelySavolainen et al Nature 441, 210-213 (2006)http://www.nature.com/nature/journal/v441/n7090/full/nature04566.htmlQED?b.socrative.com (room: UCSBBJORN)What causes allopatric speciation?Speciation mechanismsaka processesIn allopatry: genetic drift, natural selection, sexual selectionIn sympatry: negative frequency-dependent selectionEcological speciation: ecological differences drive divergence http://en.wikipedia.org/wiki/Ecological_speciationSpeciation mechanismsaka processesExample: https://www.youtube.com/watch?v=4pdiAneMMhU&feature=youtu.be&t=83Trade-offs drive resource specialization and the gradual establishment of ecotypesØstman et al. (2014) http://www.biomedcentral.com/1471-2148/14/113/abstractIncipient speciation: the first stages of speciation where the speciation processis not complete (RI)Completion: requires continued isolationCauses of reproductive isolationPunctuated Equilibrium•Eldredge and Gould (1972)•Reinterpretation of fossil record•Common Pattern is origin-stasis-extinction–Formerly explained as incomplete fossil record–E & G posited Punctuated Equilibrium – most change happens at speciation eventsPunctuated Equilibrium vs Phyletic GradualismPhenotypeTimePhenotypeTimePunctuated Equilibrium and Speciation•E & G posited peripheral isolates speciation as a potential mechanism for PE.•If species arise as peripheral isolates they may not be preserved as fossils–Small population–Rapid change(How) Can we test punctuated equilibrium?•Fossil pattern alone does not test PE.–Could be caused by incomplete record–Must use cases with complete records•Not mutually exclusive hypotheses–P.E. and phyletic gradualism are 2 extremes of a continuum–Becomes an empirical question – a question of frequencyExample of Phyletic Gradualism•Sheldon measured tail-ribs of trilobites•Found gradual increase in 8 species over 3 million yearsGradual increase in rib numberOutstanding Questions Relating to Punctuated Equilibrium•Does rapid change always take place at speciation?–Theoretical possibility (change in large populations may be rare)–Some cases are known where change occurs in large populations (rare?)–Relative frequencies are unknownOutstanding Questions Relating to Punctuated Equilibrium•What is the cause of stasis?–Constraint – species lack necessary genetic variation–Stabilizing selection – Selection against variants•Coupled with “habitat tracking”Outstanding Questions