2 Columbine Case Questions: How do flowers, pollinators, and pollination systems work?How can we identify and test different for reproductive isolation in plants?What mechanisms can act to unify members of a species and maintain separatations between members of different species in plants?These are the overarching questions addressed in the case study.Aquileqia caerulea – Colorado columbine
3 Clicker Question #1The diagram to the right is a phylogeny for 5 species in the same genus. This phylogeny shows. . .the degree to which organisms look like one another.how different organisms are related through common ancestorsthe sequence in which species evolved from left to right.the amount of change each species has experienced.which species are most closely related to the species at point M.
4 Clicker Question #2What do the lines in this phylogeny represent?The passage of timeLineages of organismsEach line represents a single speciesWhich species evolved first, second, third, etc.All of the above
5 Clicker Question #3What do the nodes (indicated by G, P, R, and M) represent in the phylogeny?Where two species hybridized.Lineages of organisms.Common ancestors of different species.The sequence in which species 1-5 evolved.None of the above.GPRM
6 1 2 3 4 5 Clicker Question #4 What does the point labeled R indicate? What does the point labeled R indicate?Species 5 in the past.Species 2 in the pastWhere species 2 and species 5 hybridized.The common ancestor of species 2, 3, 4 & 5..Where species 5 became species 2.GPRM
7 Clicker Question #5Which statement(s) below accurately describe what is happening at the nodes indicated by MRPG? (choose all that apply)Speciation is occurringMutation and natural selection are making the best new speciesOne species is turning into another species.Gene pools are becoming separated and isolated.Two species are coming together to make a new species.GPRM
8 Pre-case Thought Questions. How do flowers work? How do they play a role in maintaining separate species? Make a labeled diagram to summarize your thoughts.What are the important aspects of the interactions and relationship between flowering plants and their pollinators?What is the relationship among sister species, a common ancestor to the sister species, and reproductive isolation? Make a labeled diagram to summarize your thoughts.What is a phylogeny and what does it tell us about species?
9 1 2 3 4 5 Phylogenies are hypotheses about relationships among taxa. Branches in a phylogeny are called clades. Members of a clade share a number of features, such as similar flower structure, due to common ancestry.Nodes indicate common ancestors and points of lineage divergence (speciation).Lines represent separate lineages. Traits can change in a lineage resulting in unique traits shared by members of that lineage.This slide covers fundamentals of what a phylogeny is and how to read the lines and nodes. One can continue the example of this showing a genus with all five species sharing some common traits, species that share a more recent common ancestor will share more traits, and each species will have some unique species defining traits.Reproductive isolation maintains separate lineages.
14 Biotic Pollination Syndromes Cantherophily (beetles): white or drab, sweet scent, open bowl shapeMyophily (flies): variableSapromyophily (carion and dung flies): purple-brown, stink of decaying protein, deep trapsMelittophily (bees): variable color/no pure red, sweet scentSphignopily (hawkmoths): white or pale green, strong sweet scent, deep narrow tubes with nectarPsychophily (butterflies): red, yellow, blue, moderately strong sweet, deep narrow tubes with nectarOrnithophily (birds): bright red, no scent, wide deep tubes with nectarChiropterophily (bats): dull white or green, strong fermented scent, brush or bowl shapedThese are general features of major biotic pollination syndromes. Name of the syndrome, type of animals attracted, and floral features are provided. Although there is variation, these are general patterns.
15 Flowers and Pollinators: A structural-functional-behavioral interaction In flowering plants, floral structure has been suggested as an important mechanism for achieving reproductive isolation and promoting speciation by affecting either pollinator behavior (behavioral isolation) or pollen transfer (mechanical isolation) (Grant 1949).This slide introduces a concept developed by Grant that floral features are key elements to reproductive isolation in flowering plants.Grant, V Pollination systems as isolating mechanisms in angiosperms. Evolution 3:
16 Clicker Question #7Which form of reproductive isolation do you think would be most effective for flowering plants?A. Ecological isolation due to plants growing in different habitatsB. Behavioral isolation due to floral traits influencing pollinator behaviorC. Hybrids being sterile and unable to produce functional gametes or not being able to survive in populationsD. Biochemical isolation due to failed interaction between pollen and stigma.E. Mechanical isolation due to pollen not being successfully gathered or delivered.
18 Clicker Question #8In columbines, color would be an example of a _________ attractant and nectar would be an example of a _________ attractant.primary/secondaryfloral/pollinatorsecondary/primarybird/insectreward/visual
19 Floral nectar spurs are considered innovations that have promoted speciation and reproductive isolation in columbines through shifts in pollinators related to changes in nectar spur length. How could this work?This slide shows the phylogeny of Aquilegia and that A. formosa and A. pubescens are sister taxa.Modified from Whittall, J.B. and S. A. Hodges Pollinator shifts drive increasingly long nectar spurs in columbine flowers. Nature 447:bee pollinatedhummingbird pollinatedhawkmoth pollinatedhummingbird & hawkmoth pollinated
21 Clicker Question #9 Because they share a common ancestor. . . both columbine species share relatively few traits.both columbine species share some traits, but also have other unique features that define and reinforce each species’ as a separate lineage.both species are completely different from one another and share no traits.both columbine species will attract the same pollinators and grow in the same places.both columbine species are reproductively isolated from one another.
22 Spurs & speciesGiven the proposed importance of nectar spurs, how would you test their influence on columbine speciation?Develop an hypothesis and design an experiment to to explore potential causes and function of behavioral isolation and mechanical isolation in A. pubescens and A. formosa flowers.This slide asks students to begin developing hypotheses and experiments to test the importance of spurs in columbine reproductive isolation and, therefore, speciation.
23 In an initial study, researchers presented both columbine species in a hexagonal array with 9 of each spp. Arrays were placed near A. pubescens and A. formosa populations and pollinator visits recorded.Why did they do this?A. formosaA. pubescensThis slide provides a rough diagram to demonstrate the experimental array with both species. This initial experiment is essential to test whether pollinators showd preferences for different species.Modified from Fulton, M. and S.A. Hodges Floral isolation between Aquilegia formosa and Aquilegia pubescens. Proc. R. Soc. Lond. B. 266:
25 Experimental ResultsMean visits per flower per hour by different pollinators to A. formosa & A. pubescensThis slide shows the results of the pollinator visitation.Data from Fulton, M. and S.A. Hodges Floral isolation between Aquilegia formosa and Aquilegia pubescens. Proc. R. Soc. Lond. B. 266:
27 What can the researchers conclude so far? Experimental Data: Pollinator preferences for A. formosana and A. pubescensVisits tohummingbirdshawkmothsbeesA. formosa8185A. pubescens911519Χ257.641.88p<0.0001Data from Fulton, M. and S.A. Hodges Floral isolation between Aquilegia formosa and Aquilegia pubescens. Proc. R. Soc. Lond. B. 266:What can the researchers conclude so far?
28 What data should they collect? Why? What will the data tell them? Aquilegia pubescensNext, the researchers focused on A. pubescens. In this study, they planted two arrays of modified and control (unmodified) flowers.Array 1: pedicels for ½ of the A. pubescens flowers staked to make flowers pendant (point downwards)Array 2: spurs for ½ of the A. pubescens flowers shortened (squeezed nectar from bottom of spurs, tied & clipped spur)This slide prompts students to think about the next experiment in which the researchers focused on A. pubescens. In this study they manipulated the flower to see if there would be a change in pollinator response and effectiveness. Making the flowers pendant changes orientation and will affect how pollinators approach the flowers. Shortening the spur will alter how far pollinators can insert their head into the flower and, consequently, remove pollen. They should collect visitation data and pollen removal to assess how these alterations affect pollinator effectiveness.
29 A. pubescens Flower Manipulations Measure pollen removal as an indicator of effective pollinator visitation.These are diagrams of the manipulations to help students visualize the experiment.UnmanipulatedPendantShortened
30 Clicker Question #10Which of these hypotheses are the researchers potentially testing?If floral structural traits in A. pubescens are important for reproductive isolation, then we should expect. . .the floral modifications will have no effect on pollinator visitation and pollen removalhawkmoths will be better able to remove pollen from modified flowers.hummingbirds will be attracted to the modified flowers less than unmodified flowers.the unmodified flowers will have higher visitation and pollen removal by hawkmoths than modified flowers.
31 Clicker Question #11In the floral manipulation experiment, you should expect . . .unmanipulated flowers will have more pollen removed by hawkmoths than the others.unmanipulated flowers will have less pollen removed by hawkmoths than the others.hawkmoths will visit pendant flowers more than the others.hawkmoths will remove pollen from shortened spur flowers more than the others.None of these are expected outcomes for this experiment.
32 Clicker Question #12Experimental Data: Visits by Hyles lineata to A. pubescens with differing floral orientation.Visits toNumber of observed visitsupright51pendent5Χ245.5p<0.0001Data from Fulton, M. and S.A. Hodges Floral isolation between Aquilegia formosa and Aquilegia pubescens. Proc. R. Soc. Lond. B. 266:These results are consistent with the researchers’ prediction.A. True B. False
33 Clicker Question #13Experimental Data: Visits by Hyles lineata to A. pubescens with long or short nectar spurs.Visits toNumber of observed visitslong17short19Χ20.11pNot significantData from Fulton, M. and S.A. Hodges Floral isolation between Aquilegia formosa and Aquilegia pubescens. Proc. R. Soc. Lond. B. 266:These results are consistent with the researchers’ prediction.A. True B. False
34 These results are consistent with the researchers’ prediction. Clicker Question #14Mean number of pollen grains remaining in A. pubescens anthers after hawkmoth visitation.These results are consistent with the researchers’ prediction.A. TrueB. FalseData from Fulton, M. and S.A. Hodges Floral isolation between Aquilegia formosa and Aquilegia pubescens. Proc. R. Soc. Lond. B. 266:
35 Clicker Question #15 From these studies we can conclude that A. Orientation and color promote mechanical isolation and floral structure promotes behavioral isolation.B. The species have few floral features that would promote reproductive isolation.C. Spur length is a primary attractant and color is a secondary attractant.D. Orientation and color promote behavioral isolation and floral structure promotes mechanical isolation.E. Floral structure causes reproductive isolation after pollination occurs.
36 What about hybrids and habitats? A. pubescens typically grows at higher elevations and in more xeric habitats.A. formosa tends to grow at lower elevations and in more mesic (moist) habitats.Although they have these differences, hybrid populations of viable, reproductively functioning plants with floral traits and molecular markers characteristic of both species have been identified at intermediate elevations and habitats!How could that happen?What does it mean biologically? Evolutionarily?This slide introduces how reproductive isolation is not complete between the two species. Students should discuss and report back their thoughts on how this could happen and why it is important. Referring to a previous slide on pollinator visitation, bees can be low fidelity pollinators that visit different species., Likewise, hummingbirds or hawkmoths could occasionally visit both species. The key point to discuss is that in intermediate habitats, hybrid zones can form due to pollinator infidelity and hybrid plants growing in intermediate abiotic conditions.
37 Researchers measured floral (A & C) and genetic (B & D) traits in hybrid populations along elevation (A & B) and habitat transects (C & D). What do the data show?spur colorblade colorspur lengthblade lengthorientationA. pubescensA. formosaA. pubescensA. formosa genetic markersThis slide provides morphological (A & B) and genetic (B & D) data to support the previous two slides. The data show strong selection against floral traits in the high and low elevation habitats, but less evidence of selection against other A. formosa genetic markers in A. pubescens populations and vice versa.Figure from from Hodges, SA and ML Arnold Floral and Ecological isolation between Aquilegia formosa and Aquilegia pubescens. Poc Nat Acad. Sci USA 91:A. pubescensgenetic markersA. formosa
38 Clicker Question #16 The occurrence of hybrids indicates. . . that A. formosa and A. pubescens are really just one species.reproductive isolation does not matter for plant species.pollinator behavior is not important for maintaining species.reproductive isolating barriers are not always absolute between species.that habitat is not important for maintaining species.
39 Clicker Question #17Based upon the data in the floral manipulation studies, spurs act to maintain separate Aquilegia species by. . .causing flowers to grow in different habitatsoffering different rewards to different pollinatorsinfluencing pollen removed from and depositing on flowers.attracting different pollinators.
40 Clicker Question #18Based upon the data in the hybrid studies, habitat selection acts to maintain A. formosa and A. pubescens as separate species by. . .causing plants of the separate species to grow better in distinct habitats.offering different rewards to different pollinators based upon the habitat.causing hybrid individuals to survive as well as non-hybrid individuals in any habaitat.causing the pollinators living in different habitats to have access to different rewards.
41 Species Concepts Morphological species concept Based on physical characteristics.Simple, clear, but does not address mechanisms that separate or maintain species.Biological species conceptSpecies is a group of individuals whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring but cannot successfully interbreed with members of other speciesNot good for plants, asexual reproducers, hybrids, or extinct species.Ecological species conceptEach species occupies an ecological niche, which is the unique set of habitat resources that a species requires, as well as its influence on the environment and other species.Can be hard to determine if species have broad habitat tolerances.Evolutionary lineage (Phylogenetic) conceptSpecies should be defined based on the separate evolution of lineages.May be hard to draw delimitation.These are some of the major species concepts that have been or are in use and prompts students to consider whether production of viable hybrids prevents these form being considered different species. Most students are familiar with the biological species concept, but not aware of its botanical limitations. This slides promotes their thinking about what a species is.
42 Clicker Question #19Which species concept do you think is least applicable for A. formosa and A. pubescens?A. morphologicalB. biologicalC. ecologicalD. phylogeneticE. None of these really works.
43 Clicker Question #20 The two columbine species. . . are really just one species because their flowers are not different enough to be separate species.represent different lineages that became isolated from one another and diverged from a common ancestor.are tentatively two species until the pollinators can differentiate them better.represent different lineages but the pollinators’ inability to distinguish them will prevent further speciation.
44 EpilogueThere are floral differences that influence pollinator behavior.However, there is some pollinator infidelity and hybrid offspring between the two species are produced and survive in habitats intermediate to the typical conditions for each species.Although floral features maintain some reproductive isolation between species, habitat selection against hybrids is also a strong force maintaining reproductive isolation for both species.This slide concludes the group work for the case study and asks students to prepare a summary diagram of the case. All questions or a subset can be used.
45 End of Case Thought Questions Prepare a diagram that uses these columbines to show the relationship between pollinators and flower structure and function.Prepare a diagram that uses these columbines to demonstrate the evolutionary and ecological factors shaping the relationship between two sister species.Prepare a diagram that describes the history of these species and their common ancestor, how they may have become different, and how interactions with pollinators and habitat have shaped speciation.If we assume these species evolved from a common ancestor that was hummingbird pollinated, can you use a phylogenetic tree to diagram how traits diverged in the different ?This slide concludes the group work for the case study and asks students to prepare a summary diagram of the case. All questions or a subset can be used.