ADAPTATIONPowerPoint PresentationSlide 3Slide 4Slide 5Slide 6Slide 7II. Repeatability of AdaptationSlide 9Slide 10Slide 11Examples of convergent morphological adaptations: eyes in vertebrates and octopuses (have same parts)Slide 13III. Evolutionary ConstraintsSlide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Lack of variability Leaf BeetlesSlide 25Slide 26IV. Studying AdaptationWing displays and Zonosemata vittigeraSlide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37ADAPTATIONI. Formation of Adaptive PhenotypesA. What is adaptation?1. Noun-heritable modifications of the phenotype that confer highest fitness to those who possess the trait2. Verb-process by which favorable phenotypes increase in frequency in populations-mean fitness increases as populations become better adaptedB. How do adaptations evolve?1. Small modifications of existing structures (natural selection rarely creates an entirely new structure) 2. Preadaptation: existing structure modified into new adaptation Example: Evolution of fangs in pit vipersNonvenomousCobras, mambas and sea snakesPit vipersMouth open, strike!Mouth closedFangs evolved through-elaboration of existing bones in a snake’s skull-change in size and shape of jaw bonesVenom is modified salivary secretion3. Adaptations are often modifications that occur during embryonic developmentExample: inner ear bones of mammalsReptilesMammalsMAMMALTHERAPSIDAMPHIBIANLOBE FIN FISHII. Repeatability of AdaptationA. Idiosyncracy in Adaptation1.Idiosyncratic: NON-RELATED groups of species evolve very DIFFERENT adaptions in response to same environmental challenge -Evolution of glidingB. Convergence in Adaptation1. Convergence: UNRELATED groups of species evolve the SAME response to the same enviro challenge2. Convergence can only occur in UNRELATED groups-if RELATED groups all have the same adaptation, it is due to common ancestryExamples of convergent anatomical adaptations:Saltatory animals--all have enlarged hind limbs and shortened forelimbs for jumpingDone by: frogs, kangaroos and kangaroo ratsExamples of convergent morphological adaptations: eyes in vertebrates and octopuses (have same parts)Ex of Convergence: Eating antsall have no teeth, elongated snout, and long sticky tongueAardvarks, echidna and anteaterIII. Evolutionary ConstraintsA. Why aren’t all organisms perfectly adapted? 1. Historical constraints2. Trade-offs3. Lack of genetic variation1. Historical constraints-Previous evolutionary history may limit the options for future trait evolution or expression-prior changes may prohibit or render nearly impossible other types of changesHigher primates have undergone change in digestive tract for more carnivorous diet, now can no longer digest grass-prior changes can influence which of the available options are more likely to occur in the futureTHE EFFECT OF DESCENT IS THE LEGACY OF PAST MODIFICATION2. Trade-offsPhenotype is a compromise between optimal values for individual traitsTrade-offs in adaptive evolutionPrinciple of allocation:if total (energy, biomass, resources) is limitedthen increased investment in one trait forces decreased investment in others Seed numberIndiv. seed sizeEx: total biomass in seeds is fixed--tradeoff in number & sizeBegonia flowers & pollinatorsMalepollen rewardFemaleno rewardPollinator approaches to artificial flowersFlower number--size tradeoff3. Lack of genetic variationMay simply lack the genetic variability to evolve new adaptationsLack of variabilityLeaf BeetlesDo beetles have the ability to switch to any host plant, or are they genetically constrained?Nothing for selection to act on if all individuals have the same phenotypeExample:Many beetle species can only feed on and detoxify certain plants.Each host tribe has its own chemical defenses.Each beetle species can only detoxify and feed on certain host species.Many beetle species lack sufficient genetic variation to feed on and detoxify chemical defenses of unrelated host plants.IV. Studying AdaptationA. Testing for adaptation.1. Whether a trait is adaptive is a hypothesis that must be tested.Wing displays and Zonosemata vittigeraAre wing bars an adaptation in Z. vittigera?No mimicryMimicry deters other predatorsMimicry deters jumping spidersGreene et al. 1987Only A and B escaped predation by jumping spiders. Other predators ate all groups equally.B. The Comparative Method1. Hypotheses about adaptive significance of traits are often tested by making comparisons among species2. Without phylogenetic information there is no way to distinguish convergent adaptation from common ancestry. PHYLOGENETIC INFORMATION IS NECESSARY.3. What a phylogenetic comparative approach can tell us about adaptation•Whether adaptations are UNIQUELY derived or association with rapid diversification of a clade.Comparative MethodsA B C D E FA B C D E FDiversification Uniquely derived•Whether adaptations are convergent or persistent ancestral traits.Comparative MethodsA B C D E FA B C D E FCommon ancestry Convergent character4. Using the comparative method to study adaptationsAre larger testes an adaptation for male bats living in social breeding groups?All 17 species--Uncorrected for phylogeny11 contrasts--corrected for phylogenyP < 0.001 P =