Lecture+24-25_Discussion7_Speciation_NOTES

Lecture+24-25_Discussion7_Speciation_NOTES - Lectures 24-25...

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Unformatted text preview: Lectures 24-25 and Discussion 7: Lectures Species & Speciation Species There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved. beautiful -Charles Darwin, 'On The Origin Of -Charles Species' Species' Outline for Lect 24, Discussion 7 and Lect 25 “Speciation -- the origin of two species from a common ancestral species -Speciation consists of the evolution of biological barriers to gene flow.” Doug Futuyma (2005) Doug I. Ecological (maintenance) vs. Evolutionary (origins) explanations for species I. Ecological vs Evolutionary diversity diversity I. What is a species? • The Biological Species Concept • Speciation requires the evolution of reproductive isolation • What is reproductive isolation? “permanent” cessation of gene flow What between populations ⇒ evolutionary independence I. What are the mechanisms of reproductive isolation? • Pre-zygotic vs. Post-zygotic reproductive isolating mechanisms Pre-zygotic vs I. How does reproductive isolation evolve (i.e. how does speciation occur)? • Anagenetic (within-lineage/species) vs. Cladogenetic (lineage splitting) Anagenetic vs • Why barriers to gene flow are needed for speciation to occur • Three of the modes of speciation (allopatric via vicariance, allopatric Three via founder effect, or sympatric) via I. Maintenance vs. origin of Species MAINTENANCE OF SPECIES DIVERSITY: How do various kinds of _ecological intercations__ (competition, predation, parasitism, mutualism, etc.) influence the intercations__ number of species in a particular place at a particular time? number FUNCTIONAL, ECOLOGICAL, & SPECIES DIVERSITY IN DARWIN’S FINCHES I. Maintenance vs. Origin of Species ORIGIN OF SPECIES DIVERSITY: • • • There are 5-100 million species of living organisms alive today; Probably ≈ 500 million There have existed, but most are extinct have All of these species have descended from a single ancestor over the last 4.5 billion All years, by the repeated division of an ancestral species into daughter species years, How does this happen? _how do ancestral species split?_____ How _how Blue-black Grassquit Blue-black (Presumed ancestral (Presumed species from South American mainland) American THE EVOLUTION OF THE DARWIN’S FINCHES FROM A COMMON ANCESTOR COMMON II. What is a Species? II. A. The Biological Species Concept A. BIOLOGICAL SPECIES CONCEPT: BIOLOGICAL A species consists of groups of actually or potentially interbreeding natural species populations that are reproductively isolated from other such groups populations Two individuals are of the Two same species if they actually or potentially produce viable AND fertile offspring in the wild fertile ii.e. They can (& do) exchange .e. genes in nature genes Two individuals are members of Two different species if they do not do produce viable AND fertile offspring in the wild offspring ii.e. They do not freely exchange .e. genes in nature genes Rock pigeon Rock Rock pigeon Rock pigeon_ Rock x Zebra (male) Horse (female) _zorse (sterile)_ x II. What is a Species? II. A. Biological Species Concept, 1. Problems A. 1. How do we know if individuals in 1. How separate populations could actually or potentially interbreed? potentially Coyote Mountain Mountain Lion Lion (a.k.a. (a.k.a. Cougar, Puma) Puma) Florida Florida Panther Panther Grey Wolf Red Wolf (fertile) 1. What’s natural? What is a natural wild condition?_(coyotes & grey wild (coyotes wolves occasionally interbreed) wolves x 1. What about extinct organisms? What (you can’t get a fossil to “do it”) (you 1. What about organisms that don’t What _reproduce sexually? Such as II. What is a Species? II. A. Biological Species Concept, 2. Implications A. A species consists of groups of actually or potentially interbreeding natural species populations that are reproductively isolated from other such groups populations a. a. b. Species are breeding units that are can no longer exchange genes (no gene Species flow = _repoductive isolation_____) _repoductive Species are _evolutionary independent units________ Species _evolutionary • Individuals do NOT evolve (you have the alleles you’re born with) Natural selection acts on phenotypes of individuals, but these Natural individuals cannot evolve individuals • Populations & species DO evolve Populations DO Populations are groups of individuals of the same species that live Populations & interbreed in a particular place interbreed Species are made up of one or many populations Speciation requires the evolution of reproductive isolation; So what causes Speciation reproductive isolation and how does it evolve? reproductive c. III. Mechanisms of reproductive isolation A species consists of groups of actually or potentially interbreeding natural species populations that are reproductively isolated from other such groups populations “Speciation -- the origin of two species from a common ancestral species -Speciation consists of the evolution of biological barriers to gene flow.” Doug Futuyma (2005) Doug So speciation requires the evolution of mechanisms that limit gene flow. What are these mechanisms? flow. A. _pre-zygotic____: prevent gametes from uniting to form zygotes A. prevent 1. Spatial / geographical isolation (_allopatry____) (extrinsic isolating mechanism: imposed from the outside) mechanism: 2. Ecological isolation 3. Temporal isolation 4. Behavioral isolation 5. Mechanical isolation 6. Gametic incompatibility B. _post-zygotic___:act __after fertilization___has occurred act __after 1. Hybrid inviability 2. Hybrid sterility 3. Hybrid breakdown III. Mechanisms of reproductive isolation A. Pre-Zygotic, 1. Spatial / Geographical isolation If two species live in different places between which there is little dispersal, they may never have the opportunity to mate and exchange genes (reproductive isolation); this is spatial / geographic isolation isolation); species are _allopatric__, when they have non-overlapping distributions _allopatric__ • For species with weak dispersal abilities, a very short distance or small spatial For barrier could be sufficient to _render them allopatric__ _render • Conversely, for organisms like birds or marine invertebrates, capable of moving Conversely, long distances, allopatry may involve long distances or major barriers long For example: • The rise of the Isthmus of Panama The (3-5 MYA) shut off gene flow between the Pacific Ocean & Caribbean Sea the • The Isthmus separated previously The connected populations of snapping shrimp, so there is no longer any gene flow gene • We’ll talk more about this example We’ll later later III. Mechanisms of reproductive isolation A. Pre-Zygotic, 1. Spatial / Geographical isolation Geographic isolation is different than the other mechanisms we’ll discuss since it isn’t usually caused by the organisms themselves—it can be imposed upon them. It is an extrinsic__rather than It rather _intrinsix_(biological) isolating mechanism. _intrinsix_ Populations are not automatically new species just because they are Populations geographically isolated! They must also evolve intrinsic isolating mechanisms before we consider them new species. mechanisms However, geographical isolation plays a major role in some of the modes However, of speciation that we’ll discuss later _(allopatric speciation)_ of III. Mechanisms of reproductive isolation A. Pre-Zygotic, 2. Ecological isolation If two species use different habitats, even if their ranges overlap (_sympatry__), ), they can be _ecologically isolated__ _ecologically • This would make mating encounters rare • Even if the two species were reproductively compatible, they never Even actually mate, so they are reproductively isolated actually For example: Benthic 3-spine stickleback stickleback • live & build nests on lake bottoms on Limnetic 3-spine Limnetic stickleback stickleback • build nests in build shallows shallows • Males of different types build nests in different microhabitats; Females Males prefer nests of their same type prefer • In the lab, they’ll mate & produce fertile offspring, but in nature, they’re In reproductively isolated. These are considered _incipient species_ reproductively • If they eventually become “good species”, this will be a example of If __sympatric speciation__ (we’ll discuss this more later) __sympatric III. Mechanisms of reproductive isolation III. A. Pre-Zygotic, 3. Temporal isolation Species that breed at different times of the day, at different seasons, or in different years, cannot mate and are therefore _temporally isolated__ _temporally For example, Periodic cicadas emerge on 13 and 17-year cycles; they are For separated by 4 years so they don’t interbreed, even though they’re capable separated Blue = 17-year broods, Red = 13-year broods Red III. Mechanisms of reproductive isolation A. Pre-Zygotic, 4. Behavioral isolation Many organisms recognize members of their own species using highly specific… Many a. courtship behaviors b. songs (birds, insects) These evolve primarily by _sexual selection These _sexual c. chemical signals d. visual signals For example, male fireflies attract females of their own species (conspecifics) with For species-specific set of flashes and flying patterns species-specific III. Mechanisms of reproductive isolation A. Pre-Zygotic, 4. Behavioral isolation Species-specific flashing & mate attraction in Photinus fireflies Photinus A Photurus female eating a Photinus male Photurus Photinus III. Mechanisms of reproductive isolation A. Pre-Zygotic, 5. Mechanical isolation • No matter how hard males & females try to mate, they are so mismatched No anatomically that they cannot consummate the act; ______________________ ______________________ Mechanical isolation between Mechanical carabid beetles carabid Robber flies successfully mating III. Mechanisms of reproductive isolation A. Pre-Zygotic, 6. Gametic Incompatibility • Even if mating is successful, gametes are incompatible and _______________ Even _______________ • This form of reproductive isolating mechanism is especially important for… This especially 1. organisms that _______________________ into water organisms into 2. wind-pollinated plants that “spawn” their pollen into the air For example: Purple egg + red & purple sperm Purple • Only purple sperm fertilize red urchin purple urchin spawning red urchin sperm around egg III. Mechanisms of reproductive isolation B. Post-Zygotic, 1. Hybrid Inviability B. Post-Zygotic • Mating occurs, zygotes are formed, but because of genetic incompatibilities Mating during development, the _____________________________________ during • For example, wood and leopard frogs Rana sylvatica (wood frog) Rana pipiens (leopard frog) X Sp. 1 x Sp. 2 ⇒ NO F1 Hybrids (Inviable) Sp. NO III. Mechanisms of reproductive isolation B. Post-Zygotic, 2. Hybrid Sterility • Hybrid zygotes develop into adults, but the adults usually _________________ Hybrid _____________; so genes cannot move from one species into another -- they’re _____________ so “trapped” in the hybrids “trapped” • For example, many equine hybrids, like mules and zorses Zebra (male) Horse (female) Zorse (sterile)/Zony X Sp. 1 x Sp. 2 ⇒ F1 Hybrid (Sterile) Sp. III. Mechanisms of reproductive isolation B. Post-Zygotic, 3. Hybrid Breakdown FERTILE hybrids form between two species, but these hybrids have ___________ FERTILE __________________, or their F2 offspring are sterile (even if F2’s are produced) __________________ • So, the barrier to gene flow occurs one step further down the mating So, scheme (compared to hybrid sterility) scheme For example, Many ducks Mallard Mallard China Duck Challard X Sp. 1 x Sp. 2 ⇒ F1 viable but reduced fitness • Can mate w/either parental species • Will produce viable offspring • But females won’t mate with them :( But III. Mechanisms of reproductive isolation III. C. Summary Scientists often examine “young” or incipient species to learn about Scientists speciation, since we can see which mechanism(s) of isolation have evolved first, and how they evolved first and how The longer 2 species have been isolated, the more isolating mechanisms The are likely to evolve are So distantly-related species may have many isolating mechanisms So tigers and wolves) tigers How different should populations be How before we call them separate species? _when they can’t actually or potentially interbreed any more, can often be difficult to determine this point.__ point.__ (e.g. IV. The evolution of reproductive isolation A species consists of groups of actually or potentially interbreeding natural species populations that are reproductively isolated from other such groups. reproductively How does reproductive isolation evolve? How Darwin’s explanation in a nutshell: natural selection__causes divergence among causes “races” as a by-product, and they eventually become full-fledged species “races” The only figure in the Origin: a phylogeny__ The Origin But how do they diverge? How can selection favor the evolution of reproductive isolation, which _reduces How reproductive opportunities reproductive IV. The evolution of reproductive isolation A. Phylogenetic trees The splits in branches are called _nodes, and indicate a division of one lineage into two = speciation The positions of the nodes on the time scale (if present) indicate the times of the corresponding speciation events; not all trees are calibrated for time! Modern trees are drawn using data about the Modern similarity__of mitochondrial and nuclear DNA similarity of among species. As genetic data accumulates, trees get more accurate. trees SISTER SISTER SPECIES SPECIES The common ancestor for the group is called the _root_of the tree Sister Sister species are the most similar similar IV. The evolution of reproductive isolation A. Phylogenetic trees 3 kinds of evolutionary changes influence the shape of phylogenetic trees: 1. 2. 3. Within-lineage change (_anagenesis_ex. Within lineage d. etc_______) • natural selection + random processes (mutation, genetic drift) • Microevolution the origin of new lineages by speciation (_cladogenesis_ex. New _cladogenesis_ex. Group/split on the tree___________________) Group/split • Macroevolution the disappearance of lineages through _extinction_ex. Lineage with skull at the end_________________ end_________________ E IV. The evolution of reproductive isolation IV. B. The central problem of speciation So how does anagenesis___lead to cladogenesis_(speciation)? How can reproductive isolation arise in the first place? Does a mutation arise that makes one individual different from the others Does in his/her population, and less likely to mate successfully with them? in E IV. The evolution of reproductive isolation B. The central problem of speciation 1. Imagine two populations, one with A1A1 1. individuals, the other with A2A2 individuals individuals, 2. A1A2 individuals (hybrids) have low reproductive success or are inviable reproductive 3. These are thus “good” biological species_(no _(no gene flow btw them)_______________________ them)_______________________ 1 1 Population #1 1 1 1 11 AA 1 1 1 Population #2 A2 A2 A 2 A2 AA 1 A A1 AA 11 11 AA A1 A1 A 1A 1 AA 1 AA A 2 A2 A 2 A2 A 2 A2 A 2 A2 A 2 A2 A 2 A2 A 2 A2 A2 A2 Could these pops diverge due to a mutation Could within one of the pops that confers reproductive incompatibility? reproductive • __no. if a mutation in population number one __no. arose creating the a2 allele, the low fitness of a1a2, heterozygote would prevent the a2 allele from increasing in frequency. Same for popul 2 with a1 allele. AA A A2 Population #1 1 1 1 1 1 11 A A2 1 1 Population #2 1 AA 1 A A1 AA 11 A1 A1 A 1A 1 • Thus new species cannot evolve because a Thus 11 AA AA new allele causing reproductively incompatibility AA AA __reproductiviive incompatability spreads by selection____ So how does speciation happen? There must be a _barrier to gene flow__so that populations So selection____within a population _barrier so A2 A2 A2 A A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A2 A 2 A2 A 2 A2 can diverge through ____selection and/or drift with reproductive isolation as a byproduct. IV. The evolution of reproductive isolation B. The central problem of speciation So how does speciation happen? There must be a barrier to gene flow so that populations So can diverge through selection &/or drift (anagenesis leading to cladogenesis) can Some of the basic _modes of speciation__,or geographic conditions in which _modes reproductive isolation can evolve: reproductive In Allopatry (allopatric speciation) 1. Allopatric speciation by vicariance 2. Allopatric speciation by founder effect In Sympatry (sympatric speciation) 3. Sympatric speciation IV. The evolution of reproductive isolation C. Modes of Speciation _allopatric speciation _allopatric Via vicariance Via Allopatric speciation Allopatric Via founder effect Via _sympatric speciation speciation anagenesis Anagenesis Genetic differences cause Genetic reproductive isolation = cladogenesis_ cladogenesis Secondary Secondary contact; this last step need not happen for speciation to have occurred have IV. The evolution of reproductive isolation C. Modes of Speciation, 1. Allopatric - Vicariance A physical barrier subdivides a species range into 2 or more populations that no physical longer freely exchange genes longer • The barrier could be a river, mountain range, peninsula, deep water, ocean The current, glacier, or any kind of impassable habitat current, • Events that divide a species range are called _vicarient events______ Events _vicarient Once separated, populations can independently accumulate genetic differences Once either through (1) _natural selection (incl.sexual selection___and/or (2) genetic drift drift Example: Example: • The rise of the Isthmus of Panama (3-5 The MYA) shut off gene flow between the Pacific Ocean & Caribbean Sea (_vicariant event______) • The Isthmus separated previously The connected populations of snapping shrimp, so there is no longer any gene shrimp so flow. flow. IV. The evolution of reproductive isolation C. Modes of Speciation, 1. Allopatric - Vicariance 4-5 mya PRESENT What would be the consequences for terrestrial organisms? IV. The evolution of reproductive isolation C. Modes of Speciation, 1. Allopatric - Vicariance Caribbean Sea Pacific 6a Pacific SISTER SISTER SPECIES SPECIES Pacific Pacific Ocean Ocean Pacific 6 Caribbean 6 Caribbean Pacific 3 Caribbean 3 Caribbean 3a Pacific 5 1 2 3 4 5 6 7 • 7 sister species pairs have sister their sister species on the opposite side of the Isthmus Isthmus • 3 iinstances of within nstances ocean basin speciation 6, 3, 7 3, Caribbean 5 Caribbean 4 Caribbean Pacific 4 Pacific 1 Caribbean 1 Caribbean Pacific 2 Caribbean 2 Caribbean Pacific 7a Pacific 7 Caribbean 7 IV. The evolution of reproductive isolation C. Modes, 2. Allopatric – Founder Effect Allopatric speciation Allopatric via vicariance via Allopatric speciation via founder effect via Sympatric speciation IV. The evolution of reproductive isolation C. Modes, 2. Allopatric – Founder Effect Example: Founder effect speciation in Hawaiian “picture-wing” fruit flies (Drosophila) Drosophila heteroneura Drosophila IV. The evolution of reproductive isolation C. Modes, 2. Allopatric – Founder Effect • There are at least 106 species of There picture-wing Drosophila that are Drosophila _endemic___(live only there) to the _endemic___ to Hawaiian Islands Hawaiian • _this is a classic example of adaptive _this radiation (a rapid increase in speices diversity from a singe ancestral species)_ species)_ • These fruit flies use elaborate These courtship displays that are highly species-specific species-specific • They hardly ever mate with the wrong They species (i.e. they are _good species_) _good • The oldest emergent Hawaiian Islands The are younger than 5.6 million years and youngest are < 1 million years youngest • How did >100 displays diversify in so How little time? little IV. The evolution of reproductive isolation IV. C. Modes, 2. Allopatric – Founder Effect IV. The evolution of reproductive isolation IV. C. Modes, 2. Allopatric – Founder Effect The phylogeny of Hawaiian Drosophila Drosophila mirrors the order of appearance of the islands in pacific islands So, _dispersal by a So, few individuals to each new island as it was formed explains speciation speciation between islands between 3.4 MYA 1.8 MYA 1.3 MYA 5 MYA 0-0.7 MYA More ancient lineage More recent lineage IV. The evolution of reproductive isolation C. Modes, 2. Allopatric – Founder Effect But what about the 30-100 species that live on each But island? island? Lava flows & ______(vegetated ______(vegetated islands) formation on the Big Island of Hawaii Hawaii IV. The evolution of reproductive isolation C. Modes, 2. Allopatric – Founder Effect Once you’ve gotten to a kipuka, it’s a mean world out there... Once So there are So _islands (kipuka)_within (kipuka)_within each Hawaiian island island IV. The evolution of reproductive isolation C. Modes, 2. Allopatric – Founder Effect Most species of Hawaiian Drosophila are confined to a single kipuka Drosophila (1) Founder effects / _genetic drift___& (2) _natural selection__(slightly different (1) _genetic (2) _natural (slightly habitats on each island and each kipuka) cause the evolution of new species among among and within islands within IV. The evolution of reproductive isolation C. Modes, 2. Allopatric Summary of Allopatric Speciation Summary 1. _vicariant__allopatric speciation is caused mainly by natural selection allopatric mainly • • Once gene flow is interrupted between 2 populations, environmental Once differences between the habitats cause divergent selection differences Divergent selection (and possibly genetic drift) creates genetic differences, Divergent which in turn create either pre- or post-zygotic incompatibility (i.e. reproductive isolation evolves__) (i.e. Most of the reproductive isolation evolves while the populations are Most allopatric, so that if & when the populations come back into sympatry, they are substantially isolated (don’t have to come into contact, but if do already isolated isolated • In other words, speciation is a _by-product______________of divergent In _by-product______________of natural selection that occurs during allopatry natural 1. _founder effect___________allopatric speciation may be driven by genetic drift allopatric (especially in small, newly founded populations), along with natural selection (especially st, 2. __in both, geographic isloation is 1st, then other isolating mechanisms evolve_ 3. Allopatric speciation is thought to be the most common mode of speciation IV. The evolution of reproductive isolation C. Modes, 3. Sympatric speciation Allopatric speciation Allopatric via vicariance via Allopatric speciation via founder effect via Sympatric speciation IV. The evolution of reproductive isolation C. Modes, 3. Sympatric speciation Sympatric “populations” have completely overlapping ranges Sympatric By definition, there is no obvious geographic barrier to gene flow Reproductive isolation evolved through _ecological isolation__; the Reproductive _ecological the animals make use of different resources within the habitat, and so don’t have the opportunity to mate(using diff resources, overlapping ranges but making use of diff parts of that habitat.) ranges When you see 2 species that are currently sympatric, you need to ask: • Did they evolved reproductive isolation in _sympatry__? OR… Did _sympatry__ OR… • Did the species evolve reproductive isolation in _allopatry___, then Did _allopatry___ then subsequently become sympatric through secondary contact? subsequently __phylogenies____are essential to distinguishing between... 1. true sympatric speciation versus true versus 2. secondary sympatry following divergence in allopatry 2. IV. The evolution of reproductive isolation C. Modes, 3. Sympatric speciation Barombi Mbo in western Cameroon Example: Sympatric speciation in Example: crater lake cichlids crater • Barombi Mbo contains 11 endemic Barombi species of cichlids species • Species vary markedly in mating Species coloration and feeding behavior coloration • small (4 km2), but deep (100m) small • drained by one river that has intermittent flow drained • very stable; 10,000 years old 10,000 IV. The evolution of reproductive isolation C. Modes, 3. Sympatric speciation Alternative Hypothesis 1: Allopatric origins Alternative Allopatric and repeated colonizations of the lake and River Lake River Lake _river/lake sister _river/lake species pairs would suggest alloptaric origins______ origins______ IV. The evolution of reproductive isolation C. Modes, 3. Sympatric speciation Alternative Hypothesis 2: Sympatric speciation within the lake following a Alternative Sympatric single initial colonization of the lake single Lake _lake sister-species _lake groups would suggest sympatric origins__ sympatric IV. The evolution of reproductive isolation C. Modes, 3. Sympatric speciation Hypothesis 2 is supported…the cichlids in Barombi Mbo are grouped Hypothesis Pungu maclareni Konia eisentrauti Konia dikume Sarotherodon linnellii Sarotherodon caroli Sarotherodon steinbachi Myaka myaka Sarotherodon lohbergeri Stomatepia mariae Stomatepia pindu Stomatepia mongo Sarotherodon galilaeus LAKE SPECIES____ _RIVER SPECIES___ Conclusion: The 11 species of Barombi Mbo cichlids diverged in sympatry IV. The evolution of reproductive isolation C. Modes, 3. Sympatric speciation How did reproductive isolation evolve? How ECOLOGY MEETS EVOLUTION: Ecological isolation 1. Genetic variants within the original /initial population Genetic preferentially used specific _microhabitats__(or consumed _microhabitats__(or different prey/particular parts of lake) that selected for different traits (_disruptive selection_) different 2. These contrasting microhabitat differences may subdivide These the population, selecting against individuals that mate with variants specialized on alternative microhabitats variants 3. Key: To work, there would have to be essentially _no gene Key: flow_ between microhabitats... between • This could happen if a species had very little dispersal This potential (not the case in cichlids) potential • Or, a species could exhibit very strong preferences to diff Or, ecologies and to mate with like phenotypes (inbreeding) ⇒ _positive assortative mating (could be based on sexual traits or feeding morphology, etc)_ traits IV. The evolution of reproductive isolation C. Modes, 3. Sympatric speciation Summary of Sympatric Speciation Summary • • _even a little bit of gene flow prevents differentiation-even 1 migrant per _even generation can prevent divergence. Therefore…_ generation Sympatric speciation was dismissed as impossible by one of the founders of the Sympatric modern synthesis of evolutionary biology, and the “inventor” of the biological species concept, Ernst Mayr; therefore, no one believed it could happen until recently recently There are now some cases that appear to support _sympatric speciation There (cichlids, sticklebacks, Rhagoletis apple maggots, possibly orcas, etc.) (cichlids, However, it is thought to be rare. In most cases where sister species are However, sympatric, they likely diverged in allopatry and are now in secondary contact sympatric, Sympatric speciation may be more common in plants_, where many species are where polyploid (more than 2 sets of chromosomes); when a mutation arises that makes a plant into a polyploid, it is instantly a new species, and unable to mate with the parental type! with • • • ...
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This note was uploaded on 11/29/2010 for the course BIOLOGY 1211 taught by Professor Patricelli during the Spring '10 term at UC Davis.

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