Macroevolution Part II Allopatric Speciation TEACHER NOTES

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Macroevolution Part II: Allopatric Speciation

Looks Can Be Deceiving! One of the outcomes of evolution is the • These meadowlarks look very similar yet they are not formation of new species. What is a species? the same species. Allow the students come up with a definition and debate its merit. Several definitions of 2 • By contrast, these brittle stars look very different from macroevolution also exist depending on the one another, but they are the same species. textbook you use. • Evolving complex structures such as an eye. • Speciation • Evolution of whole communities. connect it to change in

[See SP 7.2; Essential Definition of Species Note the italics on “viable”! exist which also makes the information in the • A species is a group of interbreeding organisms that produce viable, fertile offspring in nature. second bullet need some qualifiers! Now is a • Members of a species will interbreed with one good a time as any to see if students know another but not other organisms outside of the species. (At least most of the time!) about hybrids at all and/or can list any. This 3 site has photos of the “Top Twenty” most popular hybrids: http://www.buzzfeed.com/toyota/the-20- coolest-hybrid-animals-3d8x A zebroid ( isolated population and

ion and/or genetic drift. genetic drift. ion and/or and equine) and donkra ( and zebra) are pictured. Hybrids will be revisited later as well. Macroevolution vs. Microevolution

• Macroevolution is evolution on a scale of separated gene pools. • Macroevolutionary studies focus on change that occurs at or above the level of species, in

speciation in an contrast with microevolution, which refers to 4 smaller evolutionary changes (typically described as changes in allele frequencies) within a species or population.

environment, natural select able to describe Asexual Species

Asexual Species If there is no interbreeding, how can this be a Even though asexual groups do not exchange genes, they do form species? Even though asexual groups do not recognizable groups. 5 Most have evolved from a sexual exchange genes, they do form recognizable species. Only those whose phenotyp is best adapted to the environment, groups. Most have evolved from a sexual will continue to survive. However, it makes them less adapted to species. Only those whose phenotype is best environmental change. Dandelions are asexual. The pollen adapted. sterile and the egg is diploid. LO 1.24 The student is gene frequency, change in knowledge 1.C.2] Macroevolution Part II Allopatric Speciation TEACHER NOTES

Ring Species

• A ring species is a connected series of neighboring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series. Examples forthcoming… 6 • These end populations are too distantly related to interbreed, though there is a potential gene flow betwe each "linked" species. • Such non-breeding, though genetically connected, "en populations may coexist in the same region thus closin

change in gene a "ring".

Ring Species

• Ensatina escholtzi is a salamander ring species that has a range along the coast and inside range of California. [See SP 7.2; Essential knowledge on and connect it to 7 • All along this range, the salamanders interbreed, but the salamanders on the ends of the ring do not interbreed. • Their groupings are called subspecies.

an isolated populati Ring Species

• The blue zones represent where interbreeding is occurring. If the ends of the rings, cannot interbreed how • So are there is gene flow can this be the same species? (See next slide…) 8 all along the salamander’s range, yet the ends of the

speciation in rings do not interbreed. Are they the same species?

Ring Species able to describe

They become a subspecies. 9 http://www.flickr.com/photos/davemedia/62430 40930/lightbox/

1.C.2] n and/or genetic drift. genetic drift. n and/or selectio natural frequency, change in envi ronment, LO 1.24 The student is Macroevolution Part II Allopatric Speciation TEACHER NOTES

These animals will interbreed with one another Limited Interbreeding but on a limited basis. So are they the same • Each Canis species will species? No interbreed with the domestic dog but not Why not? They do not produce VIABLE readily with one another. offspring. 10 • This is true, even when Why not? Often it has to do with meiosis, given the opportunity to do so. Thus, they are not the specifically, the do not pair same species since they do not interbreed in nature. evenly during meiosis, or gamete formation. There is a stage during meiosis that change in gene 1 has to occur called homolog pairing and

crossing over, which can not occur if chromosomes are not the same size or shape. Limited Interbreeding

• Tigers and lions will interbreed in captivity, but they do not interbreed in nature. • Lions form groups or prides and live in the grasslands • Tigers are more solitary and live in the forests. These animals will interbreed with one another [See SP 7.2; Essential knowledge 1.C.2] on and connect it to • Tiglon are products of male tigers and female lions. 11 • are the opposite cross. but on a limited basis. So are they the same species? No. How do we know? The offspring are not viable.

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an isolated populati Cladogenesis vs. Anagenesis I. Anagenesis- is the accumulation of changes in one species that leads to another species. It is the lineage of a species. Over time a species may accumulate enough changes that it is considered a species that differs from the 12 ancestral species. II. Cladogenesis-is the budding of

speciation in one or more new species from an ancesteral species that continues to exists. This results in biological diversity.

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Allopatric vs. Sympatric Speciation able to describe

Allopatric speciation- Graphic-Campbell Speciation occurs because a given group has been separated From Latin: Allo = “different” and Patric = from the parent group, usually because of a geographic Father (meaning “fatherland” in this case), so separation as time goes by. 13 Allopatric translates as “different fatherland” Sympatric speciation- meaning the varieties evolved in different speciation occurs even though the two groups are still living in the same area. geographical locations. Sym = “same” so Sympatric translates as 1 “same fatherland”

LO 1.24 The student is n and/or genetic drift. genetic drift. n and/or selectio natural frequency, change in envi ronment,

Macroevolution Part II Allopatric Speciation TEACHER NOTES

Allopatric Speciation

• First, geographic isolation occurs. This is an extrinsic isolating mechanism. • The two populations must become isolated geographically from one another. • If the groups become sympatric again one of two things result Graphic-Campbell 14 An extrinsic is a property is one that is not dependent on the organism in question. It is an external factor. population and

ronment, natural selection Allopatric Speciation

1. They become separate species, as evidenced by the fact they c in an isolated isolated an in no longer interbreed. 2. They can still interbreed, thus they remain the same species.

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Islands produce some of the most profound examples of speciation due to geographic isolation.

frequency, change in envi

Why does speciation occur after geographic isolation able to describe speciation speciation describe to able 1. The population that left the original group will hav [See SP 7.2; Essential knowledge 1.C.2] a different allelic make-up than the original species thus experiencing the “founder effect”. 2. The two groups will continue to experience different mutations. 16 3. The two groups will now experience genetic drift and different selection pressures due to living in separate and perhaps different environments.

and/or genetic drift. genetic drift. and/or connect it to change in gene LO 1.24 The student is

Adaptive Radiation

• The classic adaptive radiation example involves the finches of the Galapagos Islands. • There are 14 different species of finches and 13 main These finch populations are often referred to as islands, 3 smaller islands, and 107 rocks and islets. “Darwin’s Finches”. Also, you can find 17 varying numbers of the different species throughout the literature. Note that only 10 of ] the species are pictured here. aluate given data sets

an ongoing process. [See Adaptive Radiation

These finch populations are often referred to as “Darwin’s Finches”. This slide shows a 18 common South American ancestor and 14 other species that “radiate” from the original The student is able to ev to is able student The immigrant finch.

LO 1.26 SP 5.3; Essential knowledge 1.C.3 that illustrate evolution as Macroevolution Part II Allopatric Speciation TEACHER NOTES

Adaptive Radiation

• One would expect that each island would have only one species, however, each island has more than one species of finch and larger islands may 19 have as many as ten. • The process one species inhabiting a new area and evolving into several new species is called adaptive radiation.

The Amazing Galapagos Islands

SP 5.3; Essential knowledge One would expect one species of finches on each island but that is not true. Each island has at least three species of finches and some 20 islands as many as 10 species.

ocess. [See

Adaptive Radiation

• Lets suppose that finch species A, from South as an ongoing pr America migrates to an island . • Finch species A would undergo speciation into finch species B due to one or more of the following: Explain that there are the three most common – The Founder effect – Varying selection pressures “reasons” speciation occurs. 21 – Varying mutations

Adaptive Radiation ts that illustrate evolution ts that illustrate

• Now let’s suppose that some of the new finch species B migrate over to a second island.  (speciation) &  (migration) • The finches in this new environment are geographically isolated from the other island and now Graphic Campbell 22 will evolve into finch species C for the same three basic reasons. (Founder effect, varying selection pressures, or varying mutations.)

Adaptive Radiation

• Now some of the newly evolved finch species C  make their way to yet another new island.  • Guess what? Yep! Once again finch species C will evolve into finch species D (not shown yet) for the same three reasons. (Founder effect, varying selection pressures, or varying mutations.) 23 • But suppose some of species C make it back to the first island  (The plot thickens…)

The student is able to ev aluate given data se

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LO 1.26 1.C.3 Macroevolution Part II Allopatric Speciation TEACHER NOTES

Adaptive Radiation

• Obviously, species C is different from finch species B thus they can no longer interbreed back on the original island. • Finch species C may or may not evolve into another speci • If there is a niche similar to that of the second island, the selection pressure may also be similar and species C may 24 slow to change. • So, both first and second islands will have species C. The third island will have a new species D.

SP 5.3; Essential Adaptive Radiation

• Now lastly, lets suppose that finch species D from the third island returns to the first and second islands. ( & ) • On the second island finch species D does not change because it finds a niche similar to the third 25 ocess. [See island so no selection pressure is exerted upon it.

as an ongoing pr Character displacement refers to the phenomenon where differences among similar species whose distributions overlap geographically are accentuated in regions where the species co-occur but are minimized Adaptive Radiation or lost where the species’ distributions do not • Alas, the first island has no such niche. Now, there exists a selection pressure on finch species D causing overlap. This pattern results from evolutionary to evolve (character displacement) into species E.  change driven by competition among species • As a result, the first island now has three different species of finches. Two of which are not found on for a limited resource (e.g. food). The rationale 26 other islands (B & E). Each species has a distinct for character displacement stems from the

ts that illustrate evolution ts that illustrate habitat with different food sources. This process is called adaptive radiation and most commonly involve competitive exclusion principle, also called islands. Gause's Law, which contends that to coexist in a stable environment two competing species must differ in their respective ecological niche; without differentiation, one species will eliminate or exclude the other through competition.

The Amazing Galapagos Islands ]

27 The student is able to ev aluate given data se

So, NOW we understand how it is possible that each island has mor than one finch species. Some islands actually have as many as 10 species. Examine the map once more.

LO 1.26 knowledge 1.C.3 Macroevolution Part II Allopatric Speciation TEACHER NOTES

The Amazing Finches From the Galapagos Islands

Differences are found among beaks and feathers of the finch Darwin found 14 different spe of finches inhabiting these isla which are a result of adaptive in in radiation. 28 There are finches that eat seed cacti, insects and other interes foods. He also observed adaptive radiation among the tortoises mocking birds.

SP 5.3; Essential knowledge Finches 1-9 are all tree finches. Finch #1 is vegetarian and the others insects but they differ The Amazing Finches From the Galapagos Island in the types of insects they each eat which is in gene frequency, change also reflected in the size of their beaks. On islands where two or more of these finches ocess. [See exists, the differences in the beak size is even 1.Vegetarian Finch 8. Cactus ground finch more pronounced. Finch #2 is in a genera all 29 2. Warbler finch 9. Cocos finch 3. Large insectivorous tree finch 10. Woodpecker finch its own as its characteristics are more warbler 4. Medium insectivorous tree finch 11. Large ground finch 5. Mangrove finch 12. Sharp-beaked ground finch like. Finch #8 has its own genera as it is the 6. Small insectivorous tree finch 13. Medium ground finch only finch found on the Cocos island 700 km 7. Large cactus ground finch 14. Small ground finch from the Galapagos Islands. The second large as an ongoing pr

d connect it to change groups of finches are ground finches 10-14. Some live on seeds and the others on cactus flowers. Smaller beaks are specialized for small seeds and larger beaks for large seeds. Why would larger seeds be more abundant during a drought? They can store more water!

Example of Natural Selection Peter and Rosemary Grant conducted a study of • During droughts in the Galapagos Islands, larger seeds are mor abundant. Finches with slightly larger beaks have an advantag finches for over 20 years on an islet Daphne isolated population an since they are able to crack larger seeds. Major. They studied the medium ground finch, • Thus, natural selection favors finches with larger beaks. These ts that illustrate evolution ts that illustrate finches are more likely to survive and pass those genes on to th which is a seed eater. Its medium beak is very [See SP 7.2; Essential knowledge 1.C.2] next generation. A study conducted by Peter and Rosemary Gr 30 over a 20 year period confirmed these assertions. good a cracking small seeds which are produced in abundance during wet years. During droughts, larger seeds remain. Those finches with slightly larger beaks are at a

speciation in an advantage to crack larger seeds. Their study

concluded that natural selection selects for those larger beaks during droughts. Those birds with larger beak are more likely to survive and pass those genes on to the next generation. ion and/or genetic drift. genetic drift. ion and/or How Does Speciation Occur able to describe • So, two populations of Emphasize to students that these are the organisms are not the same species unless they can mechanisms of speciation. They explain HOW interbreed, and produce viab fertile offspring in nature. speciation occurs. Revisit the “why’s” of 31 • Each Prezygotic and speciation addressed in the first few slides of Postzygotic barrier listed lef explains HOW speciation this presentation. occurs. The student is able to ev aluate given data se

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LO 1.24 The student is LO 1.26 environment, natural select 1.C.3 Macroevolution Part II Allopatric Speciation TEACHER NOTES Prezygotic isolations (do not result in a zygote) are intrinsic isolating mechanisms.

in in Prezygotic: Ecogeographic Isolation Graphic http://www.google.com/imgres?q=Plantus+occi • Ecogeographic Isolation – Two populations have become so specialized for survival in different environments, that once dentalis+(sycamore)&hl=en&noj=1&tbm=isch the geographical barrier is removed the two species will neve again interbreed as one species. The adaptations for survival i their geographic locations prevent gene flow. &tbnid=qbC7HYS29yBgOM:&imgrefurl=http: //www.fcps.edu/islandcreekes/ecology/america 32 n_sycamore.htm&docid=7iiMHTDkfpwtTM&i mgurl=http://www.fcps.edu/islandcreekes/ecolo gy/Plants/sycamore/platanus_occidentalis2.jpg &w=239&h=360&ei=xABrUJeaEsHUqgHPno HQDg&zoom=1&iact=rc&dur=324&sig=1151 in gene frequency, change 59201469248240313&page=1&tbnh=157&tbn w=104&start=0&ndsp=18&ved=1t:429,r:12,s: 0,i:111&tx=42&ty=88&biw=1350&bih=719

Prezygotic: Ecogeographic Isolation

• The Plantus occidentalis (sycamore tree) is found in the eastern United States and the Plantus orientalis

d connect it to change (oriental plane tree) is found in the Mediterranean are • They can form fertile hybrids when artificially crossed but are so different from one another that neither tree 33 can survive in the other's habitat.

isolated population an Another example: The dragonflies Progomphus Prezygotic: Habitat Isolation obscurus and Progumphus alachuensis are

[See SP 7.2; Essential knowledge 1.C.2] Habitat isolation- tw species have develop closely related. In places where their range a preference for two different habitats. Ev overlaps, P. obscurus reproduces in streams if the species become sympatric, the whereas P. alachuensis reproduces in lakes. 34 probability that they will meet and mate is low. Another example: Two species of buckthorn Example: Bufo woodhousei and Bufo americanus are two closely speciation in an related toads. B. woodhousei prefers to reproduce in the quiet wate shrubs, Ceanothus thysifbrus and Canothus of a stream whereas B. americanus prefers to reproduce in shallow rain-pools. As a result, they remain separate species. denatus have ranges that overlap in California but C. thysifbrus is found in moist hills with good soil and C. denatus is found in drier, poor, and shallow soil. ion and/or genetic drift. genetic drift. ion and/or Prezygotic: Seasonal Isolation Another example-

able to describe Pinus radiata and Pinus muricana-are 2 closely related pine trees in California. While capable of cross breeding, they seldom do but because P. radiata sheds its pollen February and P. 35 Seasonal isolation- the two species have developed different times muricana shed its pollen in April. the year to mate. Example: There are four species of frogs from the genus, Rana, eac of these frogs mates at different times of the year so that if they are sympatric, no interbreeding occurs.

environment, natural select LO 1.24 The student is Macroevolution Part II Allopatric Speciation TEACHER NOTES

Prezygotic: Behavioral Isolation Another example: There are four species of leopard frogs (Rana). These frogs look very much alike, but they have different mating calls. When they hybridize, the embryos are 36 Behavioral isolation- If courtship behavior changes during deformed. separation, then sympatric mating will not occur and two new speci are formed. Example: Twelve fiddler crab species inhabit a certain beach in Panama. Males of each species have distinctive mating displays wh include waving claws, elevating the body, and moving around the burrow. change in gene

Prezygotic: Mechanical Isolation

37 Mechanical isolation- There is a physical or biological structure tha [See SP 7.2; Essential knowledge 1.C.2] on and connect it to prevents mating. For example differences in the size or fit of genita may not allow mating. This can be found in certain snails, insects a plants. Example: The Bradybaena shown are two different species of snail because the shells spiral in opposite directions, thus they are unable mate with one another.

Graphic Campbell Prezygotic: Gametic Isolation Another example- When Drosophila virilis and an isolated populati Gametic Isolation: The gametes are shed Drosophila americanus mate, the sperm are simultaneously but something physical or chemical prevents the sperm from immobilized so that they never reach the eggs. fertilizing the egg.

Example: Many sea urchin species shed In other cross mating of Drosophila the walls of their gametes at the same time, but remain 38 evolutionarily distinct. the vagina swell and kill the sperm before they

The formation of hybrid zygotes is reach the eggs. Point out to the students that prevented because the surface proteins of speciation in the ovule (the "lock") and sperm, or male this is a waste of gametes. Also, in the case of gametes (the "keys") of different species do not fit together. tobacco plants there are 66 species, cross pollination results in no fertilization since the

sperm nucleus never reaches the egg in the female gametophyte. Postzygotic: Developmental Isolatio able to describe The next isolating mechanisms a postzygotic meaning the zygote indeed formed. Energy and resources are wasted Another example-The eggs of fish can be in producing gametes and subsequent zygote production, y fertilized by other fish species sperm due to 39 no offspring. Developmental isolation- If fertilization occurs, the development o external fertilization. the embryo can be irregular and is thus spontaneously aborted. Example: Sheep belong to the genus Ovis and have 54 chromosomes, while goats belong to the genus Capra and have 60 chromosomes. When goats and sheep mate, they produce embryos This results in malformed embryos. that die prior to birth.

LO 1.24 The student is n and/or genetic drift. genetic drift. n and/or selectio natural frequency, change in envi ronment,

Macroevolution Part II Allopatric Speciation TEACHER NOTES occurs after mating species overcome pre- zygotic barriers (behavioral, mechanical, etc.) to produce a zygote. The barrier emerges from the cumulative effect of parental genes; these conflicting genes interfere with the embryo’s development and prevent its maturation. Most often, The hybrid embryo often dies before birth. However, sometimes, the offspring

gene frequency, develops fully with mixed traits, forming a frail, often infertile adult. This hybrid displays reduced fitness, marked by decreased rates of Postzygotic: Hybrid Inviability survival and reproduction relative to the parent species. The offspring fails to compete with

it to change in individuals, limiting genes flow between species. Graphic 40 Hybrid inviability- A hybrid is produced, but often does not make it to reproductive age because it is weak, irregular, etc. http://www.google.com/imgres?q=tumors+foun Example: When tobacco hybrids are successful, they often form d+on+tobacco+plants&hl=en&sa=X&biw=812 tumors. These tumors are located in their vegetative parts. Often no flowering occurs, thus no reproduction occurs. &bih=667&tbm=isch&prmd=imvns&tbnid=5J A7A- 8h6BrZqM:&imgrefurl=http://web.williams.ed u/Biology/Faculty_Staff/lbanta/lbanta.shtml&d ocid=xeUYYhBnBa_JTM&imgurl=http://web.

[See SP 7.2; Essential knowledge 1.C.2] williams.edu/Biology/Faculty_Staff/lbanta/Ima ges/tumor.gif&w=308&h=200&ei=j4lrUOL5B KLe2AX1v4H4Cw&zoom=1&iact=hc&vpx=5 isolated population and connect 22&vpy=376&dur=7172&hovh=160&hovw=2 46&tx=125&ty=101&sig=1151592014692482 40313&page=1&tbnh=108&tbnw=166&start= 0&ndsp=12&ved=1t:429,r:11,s:0,i:108

d/or genetic drift. genetic drift. d/or

speciation in an Just for fun: Ever heard “stubborn as a ”? Evidently are actually smart and Postzygotic- Hybrid Sterility independent or “superior” thinkers!

A male donkey is known as a “jack” and a natural selection an selection natural able to describe female donkey (or ass) is known as a jenny. So, yes—a “jackass” is indeed a male donkey. A 41 Hybrid sterility- some hybrids produce superior offspring but th offspring are sterile. burrow is a feral donkey. A mule is the Example: A mule is the result of female crossed with a ma donkey. Mules are sterile, thus there is no potential for gene flow offspring of a male (jack) donkey and a female In terms of evolution it is a dead end. The horse is on the left, th donkey is in the center and the mule is on the right. horse. A is the offspring of a cross between a female donkey and a male horse and is rare.

change in environment, LO 1.24 The student is Macroevolution Part II Allopatric Speciation TEACHER NOTES

Postzygotic: Selective Hybrid Eliminatio

Selective hybrid elimination or hybrid breakdown occur if two species are sympatric and can hybridize, and their offspring can reproduce.

One of the following two things will happen: 42 1. The hybrids are as viable or as fit as the parents and gene flow will occur and the two species will becom one again. 2. The hybrids are weaker or have lower fitness than th

parents and will be selected against. gene frequency,

Postzygotic: Selective Hybrid Eliminatio The rationale for character displacement stems from the competitive exclusion principle, also • Natural selection will select for it to change in those individuals that will mate with called Gause's Law, which contends that to their own species and the hybrids will die out. The competition coexist in a stable environment two competing between the two species will cause species must differ in their respective 43 character displacement. • Example: the offspring of rice ecological niche; without differentiation, one hybrid are not as fit as the parents. Crosses between the purebred species will eliminate or exclude the other parents will be favored. through competition.

Be sure to tell the students that some of the

[See SP 7.2; Essential knowledge 1.C.2] terminology changes from text to text. Seasonal Summary of Prezygotic Barriers isolation is also known as temporal isolation. Clarify that extrinsic mechanisms are external isolated population and connect mechanisms and intrinsic mechanisms directly affect the organism. Geographic isolation is extrinsic and the ten prezygotic and postzygotic 44 mechanisms are intrinsic.

d/or genetic drift. genetic drift. d/or When allopatric speciation occurs, usually more than one isolation Students should now know WHY speciation mechanism also occurs and more than one trait will change between speciation in an the two populations. occurs upon geographic isolation and HOW speciation occurs after geographic isolation.

Summary of Postzygotic Barriers natural selection an selection natural able to describe Graphic Campbell Hybrid sterility is reduced hybrid fertility. Hybrid breakdown is selective hybrid 45 elimination.

Postzygotic barriers keep two populations distinct, thus they are no longer the same species and can no longer interbreed to produce viable, fertile, offspring in nature. Again, when two population a allopatric and changes occur, most likely more than one of the 10 barriers will occur in the population leading to speciation.

change in environment, LO 1.24 The student is Macroevolution Part II Allopatric Speciation TEACHER NOTES

Created by:

Carol Leibl 46 Science Content Director National Math and Science