Evolution Exam 3
Explain what the BSC is. Who is responsible for it? Discuss some of the critical observations that contributed to its development (see p. 447-8 in your text).
Ernest Mayr. Reproductive isolation.
Explain what an ESU is and how you would identify an ESU, if you were doing some work to advise an NGO conservation organization.
Evolutionarily Significant Unit (a conservation biology term) Criteria: -Current geographic separation -genetic differentiation at neutral markers caused by restriction of past gene flow -locally adapted phenotypic traits caused by differences in selection
What is coevolution? What is necessary for coevolution to occur?
Evolutionary change in a trait of the individuals in one population in response to a trait of the individuals of a second population, followed by an evolutionary response by the second population to the change in the first. There must be genetic variation for characters in both species (or loci/genomes) that influence their interaction. Each species must be a selective force on the other species (i.e., affect the other's fitness) There must be a response to this selection in each species. EXAMPLE: BIG ASS PROBOSCIS CUZ DAH FLOWERS GOT A RULL LONG TUBE THING FER ITS NECTAR.
Anagenesis
Evolutionary change without splitting
What does macroevolution look at?
patterns of origination, diversification and extinction Only part of the answer (possibly)
Field goal shapes in phylogenetic tree vs gradual slanted branching
field goal - punctuated speciation and morphological change gradual slants - morphological change steady and unrelated to speciation events
Biological Species Concept (BSC)
"Groups of interbreeding natural populations that are reproductively isolated from other such groups" - Ernst Mayr Criterion: reproductive isolation = lack of gene flow •potentially interbreeding populations •reproductively isolated from other populations •functional definition, not based on appearance
Rate of Speciation (1)
(1) Look through Apr 1 notes
Do other Hawaiian organisms show evidence of diversifying in this way?Why is this more likely on a hot spot island chain than an island that was once connected to a continent?
(ans.: hot spot island chains like the Hawaiian islands were never connected to any mainland. The land arose directly from the ocean via submarine eruption. A sequence of islands then occurred because of tectonic plate movement over the hotspot. The ancestors of all species in the Hawaiian islands had to come from somewhere else. Some propagules, such as seeds, came by wind. Some birds flew there. Still other organisms could have come by attachment to bird feathers or feet. Rafting might occur between islands, but is less common for terrestrial organisms going to such an isolated archipelago like the Hawaiian Islands.]
How did freshwater benthic and freshwater limnetic sticklebacks evolve? And what did they evolve from? And how do they all differ from one another? And why might freshwater forms have less pronounced lateral plates (armor)? And what gene was recently found that explains the reduction in armor?
(ans: Eda; This gene, that basically codes for a low-plated/less armored phenotype is present at low frequencies in marine fish, but once the stickleback invaded freshwater, that standing genetic variation provided the fuel for repeated fixation of Eda and helped provide a basis for rapid, parallel evolution in sticklebacks and dramatic phenotypic change.) Some of the stickleback work is described starting on p. 478 in your text. Note that this is also one of the best examples of ecological speciation (which ironically I did not go into much detail on, even though it is a topic I am very interested in!)
In the flicker hybrid zone, hybrid fitness is equal or greater than parents, so what might be happening?
(ans: it could be that this is a primary hybrid zone (see pp. 464-467 for more info on hybrid zones, since we didn't have a lot of time to go into detail on them); here natural selection is altering allele frequencies, and the zone corresponds almost exactly with environmental factors. It is possible this hybrid zone could just go on persisting for a long time. Or the populations within it might become so different that they bid off into their own species, like the desert species, the gilded flicker, did)
Why is a root on a phylogenetic tree important?
-Lets you know which events happened before the others -Can't determine what traits are primitive and what traits are derived.
DIS WHERE ACTUAL REVIEW STARTS
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Divergent ecological adaptation contributes to speciation in many cases. This is important to know.
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If hybrids have reduced fitness relative to their parents what does this tell us about the speciation process in that case?
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Make sure you read about rates of speciation starting on p. 493.
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Species concept
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This should explain it all: http://www.youtube.com/watch?v=G6upxbgG850 [grad student video from UBC (University of British Columbia) showing the experimental ponds of Dolph Schluter who investigates the evolution of sticklebacks; Eda was discovered in his lab; to the tune of "I'm in a Boat"]
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VVVVMarch 27VVVV
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What are a few different ways in which hybrids can tell us something about the speciation process?
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Why are monophyletic groups important (think from an evolutionary perspective)?
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Why would we expect premating isolation to be less common in allopatric versus sympatric speciation? And is this the case, based on Coyne and Orr's studies with fruit flies?
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What are three main observations that suggest coevolution has occurred and is occurring? Discuss an example of each, and why and how they are suggestive of coevolution.
1. Tight correspondence between features of interacting species 2.Patterns of ecological specialization and diversity -plant adapts defenses agains bug that eats it, and the bug then adapts to tolerate the plants defenses 3.Correspondence between phylogenies of interacting species Buchnera (bacterial endosymbionts) within aphid hosts 4.Complementary sets of capabilities ex: Ant - Acacia relationship. Ants defend the Acacia from herbivores and other plants, while using the plant for food and a home.
What are three tests using genetic distance and geographic data that can help us figure out whether allopatric speciation has occurred?
1.Small, peripheral isolates should be more clearly differentiated than large, central ones 2.Closely related species should be geographically close to one another, but not overlapping 3.When closely related species overlap geographically, there should be evidence that they differentiated in isolation, and the overlap came later
How do you go about constructing a phylogenetic hypothesis? How do you indicate when different characters evolved? What kind of tree is the best, based on the principle of parsimony—the fewest changes or the most changes?
1.find as many derived characters as possible in a variety of (hypothetically) closely and distantly related taxa 2.put lists of taxa & their apomorphies into data matrix -apomorphy is a derived character
Micro Macro
:Trait freq within a beetle pop from one gen to the next :Missed it. (first fewish slides of macroevolution (Apr 1)
Describe the idea of ecological isolation. Illustrate with an example. (starting p. 451)
A.Breeding at different times of year, seasonal isolation B.Habitats vary, habitat isolation C.Breakdown of habitats can get rid of some ecological isolation a.Two closely related crickets, one reaches reproductive age in the fall, the other in spring b.Japanese ladybird species, one feeds on thistle and the other feeds on blue cohosh. c.Two species of wild iris hybridize in Louisiana where bayous and marshes have been disturbed.
BSC Advantages and Disadvantages
Advantages (separation, cohesion) •clear, testable criterion •definition includes mechanism for diversification Disadvantages: •irrelevent to asexual species
Define allopatric, sympatric and parapatric speciation. What do we think is the most common type overall? [ans.: allopatric speciation]
Allopatric Speciation- reproductive isolation evolves btw geographically isolated populations (different places) Sympatric Speciation: occurs within the geographic tange of an ancestral population (same place) Parapatric Speciation: between adjacent populations (near place)
BUFFA SPACE
Anything before this is random notes, anything after this is following the study guide.
What is the story of ants and honeydew and what does it have to do with coevolution?
Aphids feed on plant sap and excrete sugary liquid called "honeydew" and ants will feed on this. They will in turn protect the aphids. The aphids have an adaptation of their anus that holds the liquid for the ants.
What are our main goals in determining a species concept?
Being able to classify and organize organisms.
What was the key mode through which Hawaiian endemic fruit flies evolved? (allopatric speciation through dispersal or through vicariance?) Explain the evidence for this using a phylogenetic tree and a drawing of the islands. In what ways have Hawaiian fruit flies ecologically diversified?
By dispersal from one island to the next.
By what means are species evolutionarily independent?
By drift, selection, and migration
What are homologous characters? Read p. 25-27 again to remind yourself about the idea of homoplasious characters and how they can mislead us about the most correct phylogeny.
Characters that are shared by many organisms because it was passed down from the common ancestor. Homoplasious is a character evolved two or more times with no specific origin
Distinguish the idea of a "species concept" from "species criteria". Illustrate with an example (i.e. one of the concepts and its associated criteria).
Concept defines what a species is Criteria defines
How can changes in sea level fuel speciation? Illustrate your answer with an example.
Creates water barriers that allow the isolated organisms to speciate
Describe the story of the coevolution of cuckoo parasites and their bird "hosts", including the relevance to coevolution.
Cuckoos have to evolve to lay eggs with similar coloration to their "host"
How can sympatric speciation occur through polyploidy? (text starting p. 490)
Doubling of chromosome number -causes instant reproductive isolation resulting from one genetic event -incompatibility btw gametes with different chromosome numbers (parental pop and ploidy individuals) -The 3n organism becomes sterile, and is thus a new species
What are the two main modes through which alloptraic speciation can occur? Describe each one and give specific examples to fully illustrate your answer.
Dispersal (founder speciation)- Mountain formation, River formation, Sea level change. Drosophila closely related species should be on adjacent islands Vicariance (development of a natural barrier) Snapping shrimp separated by panama
How are geographic barriers important in the process of speciation? How did isolation play a role in the evolution and conservation of Ozark collared lizards. Explain what happened.
Geographic barriers separate a species, this causes the two groups to diverge from one another (not all the time) and become less similar genetically. Ozark Collared lizards: -isolated populations/drift -7 genotypes, most have 1 -fixed/dominant allele varied
Slow cladogenesis
Gradual cladogenesis - change in species accompanied by change in morphology
On what type of characteristics are phylogenies ideally based? [synapomorphies or shared derived characters] Define "synapomorphy/shared derived character": ______.
Homologous features with a single shared evolutionary origin
Explain sympatric speciation by Rhagoletis (make sure you read the text also, p. 489-9)
Host shifts in parasites or herbivorous insects Rhagoletis pomonella populations are diverging into species that are specialized for parasitizing fruits of apple versus hawthorn One species will only lay eggs on the fruit they are born from. They also now breed at different times
Why is the Order Pachydermata no longer used? Explain.
It was an order based off of similarities in morphology, but the organisms in the order ended up not being related to each other, thus the orders were changed.
Bush and ladder patterns
Ladder: implies continuous transformation, gradual linear sequence Bush: lateral stepping, each path is one among a number of alternatives (punctuated equilibrium)
Is speciation an adaptive process? Explain why or why not.
NO, Reproductive isolation occurs as a byproduct of genetic changes that happen for other reasons. Speciation is an accidental, non-adaptive consequence of divergence among populations.
Does one single species concept work for every species in all cases? Explain why or why not using a couple examples.
NO, a species concept could be different depending on who is deeming the species a species based off of their own belief on what a species is. EX....... Defining a bacterium would be different than a fossil
Stasis
No significant, directional evolutionary change Prevalent across the history of life
In the ongoing process of coevolution, do all parasite traits favored by selection also benefit the host species? Explain your answer using an example.
No, the
Does a tree necessarily represent all the taxa possible on that tree?
No?
Rate of Speciation (2)
Number of species, per ancestral species, that arise per unit time Rate of increase depends on both rate of origination and rate of extinction
Explain the process of sympatric speciation and illustrate with an example. What are the steps through which it is thought to occur?
Occurs within the geographic range of an ancestral population. -Intraspecific competition for resources -Coexisting population (exploit diff resources) -adaptation to the resource -Can lead to heterozygote inferiority -Selective advantage for assortative mating (divergent natural selection against intermediates) -Increases divergence in ecologically relevant trait(s) Threespine sticklebacks (a) Marine species (b)Limnetic species in freshwater (c)Benthic species in freshwater
If stasis is common at the species level, how do evolutionary trends (directional shifts over time) develop?
Origination (birth) bias: differential production of species Directional bias: channeled production in one direction Extinction (death) bias: differential extinction of species There are diagrams for these (phylogenetic trees)
Describe and draw what parapatric speciation is and illustrate with an example.
Parapatric speciation: between adjacent populations -Range expansion along a gradient -broad ranges with gene flow only among near populations RING SPECIES
Macroevolution
Patterns of evolutionary change at and above the species line Hierarchy - genes, individuals, pop, species, lineage.
slow anagenesis
Phyletic gradualism - continuous morphological change
What is speciation? Describe the three basic stages through which it generally occurs.
Populations diverge and split into species Stages 1.Populations become isolated 2.Trait divergence among isolated populations (genetic & ecological) 3.Secondary contact between the populations a.If gene flow is limited/ceased: speciation is initiated (reproductive isolation) b.If strong gene flow, populations will collapse back.
Barriers to gene flow are an important part of the speciation process. What are the ways in which barriers to gene flow can exist? (e.g. name types of prezygotic and postzygotic barriers and illustrate with examples; look in your text as well).
Prezygotic -lock and key don't fit - Not synchronized in mating -Courtship behavior Postzygotic -Hybrids are sterile -hybrids are non-viable
other species concepts
Recognition concept - share common fert. mechanisms \ evolutionary concept- share lineage
Why is secondary contact important? What does it tell us?
Reinforcement - if populations have diverged sufficiently in allopatry, their hybrid offspring should have reduced fitness relative to the parent populations -reduced hybrid fitness = reinforcement for assortative mating, promotes continued divergence -speciation would result (complete reproductive isolation) Hybridization -can thrive and eventually erase the divergence -can develop new characters and form distinct population of their own (can get 3 species) -hybrid fitness can be equal to/greater than parents
What are some examples of "misfits" that present difficulties for some of the most used species concepts? Why are they "misfits" with respect to certain species concepts?
Reproduction via mitosis •asexuals -species defined by sets of diagnostic traits -under BSC, each clone would be a different species •Bacteria & Viruses -Defined by morphology, pathology, antigenic properties -mosaic gene structure (gene transfer) -Under BSC, no genetic isolation so all be one or a few species?
What is a root? A node? A monophyletic vs. paraphyletic vs. polyphyletic group? Indicate them on a tree.
Root: Ancestral characteristic Node: most recent common ancestor (mrca) Monophyletic: includes all of the species descending from a common ancestor (none excluded) Paraphyletic: does not contain all descendants of the mrca, some fall outside (C) Look at slide to see "C" Polyphyletic: doesn't contain the mrca
More generally, describe the four different types of species criteria that were mentioned in class. Give specific examples of each one. You may draw diagrams if you wish.
Separation- time, space Cohesion- ecological and genetic Monophyly- separation by most recent common ancestor Distinguishability- genetic and phenotypic clusters, and anything you can visually see.
Describe the idea of behavioral isolation. Illustrate with an example (e.g. how might male color patterns and related characteristics in hummingbirds contribute to reproductive isolation among the different hummingbird species?) . How might behavioral isolation happen in plants, since we don't always think of them as "behaving"? Check out the example of the famous species of Mimulus (pp. 452-454)
Sometimes referred to as sexual isolation. An important barrier to gene flow among sympatric species that may frequently encounter each other but simply so not mate. Morphologically similar green lacewings will sing at different frequencies and unless the female sings back to the male (she can only hear males of her species) no mating will occur. In Humming birds, coloration, tail feathers and crest formation keep the species reproductively isolated Mimulus species are pollinated by different organisms, thus they are kept reproductively isolated.
What unites Micro and Macroevolution
Speciation
What is going on with those banded water snakes? What could happen to some of the island populations if gene flow was completely cut off (e.g. by change in water currents)? Are incipient species more likely to evolve on the mainland or small islands? Why? (also check out the idea of "peripatric speciation" (NOTE: different from Parapatric!) by Mayr and the evidence for it pp. 484-486 in your text; and see figure 18.18)
Speciation, small islands
Why does stasis occur?
Stabilizing selection damping effects of gene flow developmental stability lack of genetic variation *need to be mutually exclusive
Macro evolutionary patterns Tempo & Mode
Tempo - rapid vs slow Mode - cladogenesis vs anagenesis
what is species criteria?
The criteria that we used to place species
What is a phylogeny? What is systematics and how does it differ from traditional taxonomy?
The evolutionary history of a group
Describe the processes by which postmating barrier might evolve.
The offspring produced are either not viable, or will be sterile
Discuss in some detail the example from class about the deep sea fish with the different family names. What did this set of problems illustrate with respect to species concepts?
They are part of the same species, but they look very different at different stages of live, and male to female. They fit into BSC, but not morphological species concept
Why are reproductive isolating mechanisms important? What are the two major categories of reproductive isolating mechanisms? Describe each one.
They are reasons for distinguishing two species from one another in BSC and PSC. •Prezygotic -premating -prevents formation of hybrid zygotes •Mechanical - lock and key don't fit •Ecological - Don't encounter each other during breeding times (not synchronized) (Ex: Cicadas: one species breeds every 17 yrs, another every 13) •Behavioral - Attract mates -courtship behavior •Postzygotic -Postmating -Reduce viability or fertility of hybrids •Sterile Hybrids (mule = horse x donkey) •non-viable hybrids
In the tree we looked at in class, does it say that "Lions evolved from tigers"? What does it say?
They evolved from the same common ancestor
How were species concepts involved in the discovery of cryptic species of copepods?
They were recognized as 1 species with a broad distribution. According to BSC, and PSC show that they are more than one species, this was due to abilities of certain copepods to mate with one another.
Relevance of the Madagascan orchid Darwin saw.
This orchids nectar-bearing spur was 24cm long. Darwin predicted that there must be a moth with a similarly long proboscis. He was right, it was the long-toungued sphinx moth. Both organisms live in Madagascar, if that wasn't already obvious.
Based on what we discussed in lecture, why wouldn't a platypus, a turtle and a toucan be a good taxonomic group, if we based it on their mutual toothlessness?
This would be a bad taxonomic group because they can not interbreed, and they are genetically very different. Each of their relatives had teeth
Explain the vicariant mode of allopatric speciation and how the Isthmus of Panama was involved. Illustrate with an example. Which populations would be isolated first—deep water species or shallow water species? Why?
Vicariance splits a species' distribution into isolated units Isthmus of Panama was created ~3 mya, separating the shrimp. Not rapid. Species living in deep water would be isolated first Species with less motile larvae would be isolated first
Are species concepts sometimes congruent?
Yes. Example, the BSC and PSC are congruent for copepods.
How might species concepts be relevant in conservation management decisions? Illustrate your answer with the example of the red wolf. Can you think of other examples that illustrate why species concepts might be important in conservation biology?
You need to be able to group organisms into a specific species so you can quantify the species and know exactly how many individuals there are and be able to gage their health off of that. This is necessary in con bio so you know what organisms need saving. EX: Red wolf -Few individuals left , many were coyote-wolf hybrids -capture 14 "pure" wolves, captive breeding -BSC- species status of red wolf is questionable -Morph. research shows - prior to 1930's red wolf distinguishable traits, hybridization was recent and due to circumstance -genetic studies- no clear diff btw red wolf & coyote, red wolf is hybrid of coyote & gray wolf -BSC & PSC - not a "good species" -Do we spend public money on the red wolf? Still reintroduce?
What are our main goals in determining a species concept?
a definition that is mechanistic, testable, and a classification system that accurately reflects evolutionary history
How does stasis occur
damping effects of gene flow - in widespread... ... developmental stability - internal "resistance" to change lack of genetic variation - (horseshoe crab vs. other arthropod clades)
Anagenesis
evolutionary change without splitting
What are the advantages and the disadvantages of the BSC? Of a morphological species concept? Of the PSC?
mentioned above, but PSC - testable, quantifiable, shows the evolution of the group BSC - testable, shows a mechanism Morpological - good for I.D. bad because its based on looking at the organism, no mechanism
What is macroevolution?
more dramatic biological changes (origin of different species, the extinction of species, and evolution of major features) Maybe try this definition from quizlet?
If you had to point out exactly where on a tree speciation occurs (and is depicted schematically), where would it be?
node
Rapid anagenesis
punctuated anagenesis - change in morphology but no speciation
Rapid cladogenesis
punctuated equilibrium - long periods of stasis
Stabilizing selection
selection against the extremes, for intermediates punctuated anagenesis (stairway pattern of speciation)
Describe what a ring species is.
series of neighboring populations close ones can interbreed two ends can't
Using the bryozoan example we talked about in class, show how species concepts used in Recent (a.k.a. "modern," not extinct) taxa can also apply to fossils
skeletal measurement to distinguish morphospecies, same approach used with living forms, but the differences could be based on environment which could alter a fossils species able to look at protein differences but not genetic
Cladogenesis
splitting of evolutionary lineage
Cladogenesis
splitting of evolutionary lineage (ancestor & Descendants co-occur)
Define what a clade is.
taxon = clade = group of organisms with a common evolutionary ancestry
BCS,morphological species, PCS
they have to reproduce together. can't test fossils, certain plants dont directly "mate" Based off physical characteristics good for field I.D. Bad because it leaves out the genetics Looking at a larger group with most common ancestors, there could be multiple species Uses genetics to form the species
Example of diversification of plant defenses and insect counter-adaptations.
• Ehrlich & Raven 1964 proposed that coevolution of plant defenses and insect counter-adaptations spurred the diversification of both, through these steps: 1. Plants are attacked by insect herbivores, and selection favors the evolution of protective chemical defenses (toxins). 2. Protected plants increase in abundance and radiate 3. Insect lineage evolves ability to overcome plant defense. 4. This lineage becomes abundant and radiates, due to lack of competition 5. Plants evolve a further defense against the new herbivore type. Etc.
Stasis, Anagenesis, Cladogenesis Graphs
•Stasis: (x-form, y-time) Positive slope going from ancestor to descendent. This pattern is rare within a species. Evolutionary stability •Anagenesis
Species Criteria
•separation - groups must be separated: in space, in time, in behavior •cohesion - group must be cohesive, ecologically and genetically •monophyly - group must share a most recent common ancestor •distinguishability (3 types) -diagnosable: set of fixed traits (taxonomic key) -Phenetic cluster: trait overlap with a few distinguishing traits -Genetic cluster: morphological indistiguishable but genetically distinct clusters