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Do you think Speciation can only be observed over millions of years

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1 Do you think Speciation can only be observed over millions of years
Do you think Speciation can only be observed over millions of years? Explain.

2 Do you think species are going extinct, but no new species are forming on Earth?
Yes No Explain your answer.

3 What is a Species? A Case Study
Image Credit Description: Rhagoletis pomonella (male and female apple maggot flies) Source: Author: Jack Kelly Clark Licensing: Photo of Rhagoletis pomonella from UC IPM Pest Management Guidelines: Apple, UC ANR Publication Used with permission from University of California Statewide IPM Program (http://www.ipm.ucdavis.edu).

4 The Apple Maggot Fly Rhagoletis pomonella Image Credit
Description: Rhagoletis pomonella (male and female apple maggot flies) Source: Author: Jack Kelly Clark Licensing: Photo of Rhagoletis pomonella from UC IPM Pest Management Guidelines: Apple, UC ANR Publication Used with permission from University of California Statewide IPM Program (http://www.ipm.ucdavis.edu).

5 Hawthorn trees are native to North America.
The hawthorn fruit is eaten by the larvae of the hawthorn maggot fly, Rhagoletis pomonella. Image Credits Description: Hawthorn tree Source: Wikimedia Commons, Author: Sannse Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License. Description: Rhagoletis pomonella (male and female apple maggot flies) Source: Author: Jack Kelly Clark Licensing: Photo of Rhagoletis pomonella from UC IPM Pest Management Guidelines: Apple, UC ANR Publication Used with permission from University of California Statewide IPM Program (http://www.ipm.ucdavis.edu). 13 mm average Size fruit

6 Rhagoletis pomonella life cycle
The female lays fertilized eggs in the fruit. Maggots (larvae) emerge from the egg, feed on the fruit, and grow . Healthy maggots drop from the tree with the fruit and burrow in the soil. Pupation takes place in the soil. 4. Adult maggot flies emerge from the soil and fly to fruit trees, where they mate on the surface of the fruit. On separate sheet Image Credit Description: Rhagoletis pomonella (male and female apple maggot flies) Source: Author: Jack Kelly Clark Licensing: Photo of Rhagoletis pomonella from UC IPM Pest Management Guidelines: Apple, UC ANR Publication Used with permission from University of California Statewide IPM Program (http://www.ipm.ucdavis.edu).

7 But there are parasites!
Parasitoid wasps try to lay eggs in the maggot’s body, paralyzing and ultimately killing the maggot. Image Credit Description: Parasitoid wasp Source: Wikimedia Commons, Author: Richard Bartz Licensing: Licensed under the Creative Commons Attribution ShareAlike 2.5 License.

8 Apples Domesticated apples (Malus domesticus) were introduced to North America in the 1600s. They are now the most widely grown fruit in North America. A typical commercial apple has a diameter of 70 mm. Image Credit Description: Empire apples Source: New York Apple Association, Licensing: Courtesy of © New York Apple Association (http://www.nyapplecountry.com).

9 Rhagoletis Host Shift Hawthorn (Crataegus spp) Rhagoletis pomonella
♀ lays eggs on fruit Hawthorn (Crataegus spp) Rhagoletis pomonella Image Credits Description: Rhagoletis on apple Source: Penn State Department of Entomology Image Gallery, Author: Larry Hull Licensing: Images in this gallery have been contributed by individuals committed to the enhancement of teaching and learning. The images may be freely used by faculty, students, and staff for non-commercial educational purposes. Description: Hawthorn tree Source: Wikimedia Commons, Author: Sannse Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License. Description: Apple tree Source: Wikimedia Commons, Author: Original uploader was Mistman123 at en.wikipedia Licensing: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation license, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. 1864: First noted apple Infestation (147 years Ago) Apple (Malus domesticus)

10 Apple vs. Hawthorn: The Maggot’s Viewpoint
The large apple fruit provides 220 times more food than hawthorn fruit. But the nutritional quality of hawthorn fruit is superior: 52% of hawthorn maggots survive vs. 27% of apple maggots.

11 Apple vs. Hawthorn: The Risk of Attack
Larger fruits of apples are much deeper than hawthorn fruits. Apple maggots can burrow to avoid parasitoid wasps. Apple maggots carry fewer parasitoid wasp eggs than hawthorn maggots do. Image Credit Description: Parasitoid wasp Source: Wikimedia Commons, Author: Richard Bartz Licensing: Licensed under the Creative Commons Attribution ShareAlike 2.5 License.

12 Today: There are Hawthorn & Apple Maggot Flies
Hawthorn and apple maggot flies are physically indistinguishable. However, they are genetically distinct, with different genetic profiles. There is no geographic isolation or physical separation between hawthorn and apple maggot flies.

13 Hawthorn & Apple Maggot Flies
Maggot flies tend to mate with their own kind. Hawthorn maggot flies strongly prefer to mate on and lay fertilized eggs in hawthorn fruit. Apple maggot flies strongly prefer to mate on and lay fertilized eggs in apple fruit. There is only a 4-6% hybridization rate between hawthorn and apple maggot flies.

14 Rhagoletis Host Shift Hybrids are viable and fertile.
Apple-raised Hawthorn-raised Image Credits Description: Rhagoletis on apple Source: Penn State Department of Entomology Image Gallery, Author: Larry Hull Licensing: Images in this gallery have been contributed by individuals committed to the enhancement of teaching and learning. The images may be freely used by faculty, students, and staff for non-commercial educational purposes. Description: Hawthorn fruit Source: UBC Botanical Garden and Centre for Plant Research, Licensing: Licensed under the Creative Commons Attribution-Noncommercial 2.0 Canada License. Description: Red Delicious apple Source: Wikimedia Commons, Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License. Hybrids are viable and fertile. No post-zygotic barriers

15 Timing of Host Fruit Ripening
Different ripening time of host fruit leads to temporal separation of apple and hawthorn flies. Image Credit Description: Emergence of Rhagoletis pomonella Source: National Center for Case Study Teaching in Science, Author: Jim Stamos, adapted from G. L. Bush, Sympatric host race formation and speciation in frugivorous flies of the genus Rhagoletis (Diptera: Tephritidae), Evolution 23:237–251, 1969. Licensing: Used with permission.

16 Based on the information provided, are hawthorn and apple maggot flies separate species? Explain your reasoning. Answer with group and discuss. Yes because….. No, because….. Not sure, we need more informaiton.

17 Image Credit Description: Mating Adelé penguins Source: Wikimedia Commons, Author: Mila Zinkova Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License.

18 1. According to the biological species concept, are hawthorn and apple maggot flies separate species? Students explain and I write responses on board

19 Which information is relevant to the biological species definition?
Hawthorn and apple maggot flies are physically indistinguishable. There is a 4-6% hybridization rate between hawthorn and apple maggot flies. Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

20 Ecological species concept
A species is a set of organisms exploiting a single niche. The key aspects of this definition are the resources exploited and the habitat occupied by the members of a species. Image Credit Description: Predatory jungle cat, Felis chaus Source: Wikimedia Commons, Licensing: The copyright holder has irrevocably released all rights to this image, allowing it to be freely reproduced, distributed, transmitted, used, modified, built upon, or otherwise exploited in any way by anyone for any purpose, commercial or non-commercial, with or without attribution of the author.

21 2. According to the ecological species concept, are hawthorn and apple maggot flies separate species? Explain why?

22 Which information is relevant to the ecological species definition
Which information is relevant to the ecological species definition? Explain. Hawthorn and apple maggot flies are physically indistinguishable. There is a 4-6% hybridization rate between hawthorn and apple maggot flies. Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

23 Morphological species concept
A species is a set of individuals with morphological features in common. The key aspect of this definition is the morphology of the members of a species. Individuals of a species are morphologically similar to one another, yet morphologically distinct from individuals from another species. Image Credit Description: Shiitake mushroom Source: USDA ARS Photo Library, also at Author: Keith Weller Licensing: This image is in the public domain because it contains materials that originally came from the Agricultural Research Service, the research agency of the United States Department of Agriculture.

24 3. According to the morphological species concept, are hawthorn and apple maggot flies separate species?

25 Which information is relevant to the morphological species definition?
Hawthorn and apple maggot flies are physically indistinguishable. There is a 4-6% hybridization rate between hawthorn and apple maggot flies. Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

26 Phylogenetic species concept
A species may be defined by its unique genetic history as a tip of a phylogenetic tree. Species are defined by their unique derived features and shared ancestry. Image Credit Description: Cladogram Source: Wikimedia Commons, Author: Fred Hsu Licensing: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation license, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.

27 4. According to the phylogenetic species concept, are hawthorn and apple maggot flies separate species?

28 Which information is relevant to the phylogenetic species definition?
Hawthorn and apple maggot flies are physically indistinguishable. There is a 4-6% hybridization rate between hawthorn and apple maggot flies. Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

29 Reproductive isolation
5. How do two similar species maintain genetic isolation if they come (or remain) in contact with each other?

30 Reproductive isolation
Reproductive isolating mechanisms prevent two individuals from distinct species from interbreeding or produce viable and fertile hybrid offspring.

31 Image Credits Description: Mountain range Source: Wikimedia Commons, Author: Kogo Licensing: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation license, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. Description: River Source: Wikimedia Commons, Author: Fabien Léonard Description: Glacier Source: Wikimedia Commons, Author: Ben W. Bell Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License. Description: Blue Jay Source: Wikimedia Commons, Author: Mdf

32 Sympatric speciation In sympatric speciation, there is no geographic barrier to gene flow.

33 6. Explain what type of Speciation is occuring or has occurred with Rhagoletis based on the evidence given. Image Credit Description: Rhagoletis on apple Source: Penn State Department of Entomology Image Gallery, Author: Larry Hull Licensing: Images in this gallery have been contributed by individuals committed to the enhancement of teaching and learning. The images may be freely used by faculty, students, and staff for non-commercial educational purposes.

34 7. What reproductive barriers limit interbreeding between hawthorn and apple maggot flies? Explain.
Choose between - Mechanical isolation Habitat isolation Temporal isolation Hybrid breakdown

35 Timing of Host Fruit Ripening
Different ripening time of host fruit leads to temporal separation of apple and hawthorn flies. Image Credit Description: Emergence of Rhagoletis pomonella Source: National Center for Case Study Teaching in Science, Author: Jim Stamos, adapted from G. L. Bush, Sympatric host race formation and speciation in frugivorous flies of the genus Rhagoletis (Diptera: Tephritidae), Evolution 23:237–251, 1969. Licensing: Used with permission.

36 8. Are apple and hawthorn maggot flies a separate species?
Are they in the process of speciating? At what point is it reasonable to say that speciation has occurred?

37 Genetic divergence Genetic divergence is the accumulation of genetic differences between two populations.

38 Evolutionary Significant Units

39 Factors causing genetic divergence between isolated populations
Founder effect Mutation Genetic drift Differential selection

40 Reproductive isolation
Reproductive isolating mechanisms prevent two individuals from distinct species from interbreeding or produce viable and fertile hybrid offspring.

41 Image Credit Description: Sperm Source: Wikimedia Commons, Author: Gilberto Santa Rosa from Rio de Janeiro, Brazil Licensing: Licensed under the Creative Commons Attribution 2.0 Generic License. Description: Egg cell Source: Wikimedia Commons, Author: Faithful reproduction of a lithograph plate from Gray’s Anatomy Licensing: This image is in the public domain because its copyright has expired. Description: Frogs in amplexus Source: Wikimedia Commons, Author: Rainforest_harley Licensing: Licensed under the Creative Commons Attribution-Share Alike 2.0 Generic License. Description: Fertilization Source: Wikimedia Commons, Licensing: Believed to be in the public domain.

42 Reproductive isolation: Prezygotic barriers
Habitat isolation Behavioral isolation Temporal isolation Mechanical isolation Gametic isolation

43 PRE-reproduction barriers
Obstacle to mating or to fertilization if mating occurs geographic isolation ecological isolation temporal isolation behavioral isolation mechanical isolation gametic isolation

44 Ecological isolation Species occur in same region, but occupy different habitats so rarely encounter each other reproductively isolated 2 species of garter snake, Thamnophis, occur in same area, but one lives in water & other is terrestrial

45 Temporal isolation Species that breed during different times of day, different seasons, or different years cannot mix gametes reproductive isolation sympatric speciation “same country” Eastern spotted skunk (L) & western spotted skunk (R) overlap in range but eastern mates in late winter & western mates in late summer

46 Behavioral isolation Unique behavioral patterns & rituals isolate species identifies members of species attract mates of same species  courtship rituals, mating calls reproductive isolation The most comedic species of the Galapagos Islands is the Blue Footed Booby, what a ridiculous outfit and expression! Their name is in fact taken from the Spanish 'bobo' which means clown. The Blue Footed Boobies above display part of their humorous courtship ritual whereby they raise their feet one at a time and then swivel their heads away from the prospective mate looking to the sky. Other interesting Booby features are the highly evolved airbag systems in their skulls which allow them to dive bomb into the sea for fish from great height, and the egg and hatchling nesting boundaries they make which are rings of Boobie poop. They aren't the only Booby on the island — there are also Masked and Red Footed Boobies about. Blue footed boobies mate only after a courtship display unique to their species

47 Mechanical isolation Plants
sympatric speciation? Morphological differences can prevent successful mating reproductive isolation Plants Even in closely related species of plants, the flowers often have distinct appearances that attract different pollinators. These 2 species of monkey flower differ greatly in shape & color, therefore cross-pollination does not happen. The most comedic species of the Galapagos Islands is the Blue Footed Booby, what a ridiculous outfit and expression! Their name is in fact taken from the Spanish 'bobo' which means clown. The Blue Footed Boobies above display part of their humorous courtship ritual whereby they raise their feet one at a time and then swivel their heads away from the prospective mate looking to the sky. Other interesting Booby features are the highly evolved airbag systems in their skulls which allow them to dive bomb into the sea for fish from great height, and the egg and hatchling nesting boundaries they make which are rings of Boobie poop. They aren't the only Booby on the island — there are also Masked and Red Footed Boobies about.

48 Mechanical isolation Animals
For many insects, male & female sex organs of closely related species do not fit together, preventing sperm transfer lack of “fit” between sexual organs: hard to imagine for us… but a big issue for insects with different shaped genitals! The selection is intense because it directly affects offspring production -- it is affecting sex itself Damsel fly penises

49 Gametic isolation Sperm of one species may not be able to fertilize eggs of another species mechanisms biochemical barrier so sperm cannot penetrate egg receptor recognition: lock & key between egg & sperm chemical incompatibility sperm cannot survive in female reproductive tract Sea urchins release sperm & eggs into surrounding waters where they fuse & form zygotes. Gametes of different species— red & purple —are unable to fuse.

50 Reproductive isolation: Postzygotic barriers
Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown

51 When a male donkey mates with a female horse, the hybrid offspring is an infertile mule. Explain what type of reproductive barrier this is. X The reproductive barrier is a. prezygotic b. postzygotic Image Credit Description: Mule Source: Wikimedia Commons, Author: Einar Faanes Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License.

52 Reduced hybrid fertility
Even if hybrids are vigorous they may be sterile chromosomes of parents may differ in number or structure & meiosis in hybrids may fail to produce normal gametes Mules are vigorous, but sterile What’s wrong with having 63 chromosomes? Odd number! Cannot pair up in meiosis. Horses have 64 chromosomes (32 pairs) Donkeys have 62 chromosomes (31 pairs) Mules have 63 chromosomes!

53 Reduced hybrid viability
Genes of different parent species may interact & impair the hybrid’s development Species of salamander genus, Ensatina, may interbreed, but most hybrids do not complete development & those that do are frail.

54 Hybrid breakdown sympatric speciation? Hybrids may be fertile & viable in first generation, but when they mate offspring are feeble or sterile In strains of cultivated rice, hybrids are vigorous but plants in next generation are small & sterile. On path to separate species.

55

56 The antennae of male moths can only detect sex pheromones released by a female in his species. Explain this reproductive barrier. This reproductive barrier is: Prezygotic Postzygotic Image Credit Description: Luna moth antennae Source: Wikimedia Commons, Author: Pollinator, Fairfield Glade, TN July 2003 Licensing: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.

57 Question Would you expect natural selection to favor pre-zygotic or post-zygotic isolating mechanisms between sympatric species?

58

59 Graphic of salamanders - ring species idea, or other.
Suppose two long separated populations had an opportunity for renewed contact with each other. explain the possible outcomes? 1. No speciation - individuals hybridize fully 2. full speciation – individuals don’t hybridize at all. 3. individuals hybridize, but offspring have reduced fitness – speciation in progress.

60 In terms of post and prezygotic reproductive barriers, Habitat isolation and temporal isolation are:

61

62 Notes and outs Follow will go on an information sheet that students will have at each table.

63 Rhagoletis pomonella life cycle
The female lays fertilized eggs in the fruit. Maggots (larvae) emerge from the egg, feed on the fruit, and grow through several molts. Healthy maggots drop from the tree with the fruit and burrow in the soil. Pupation takes place in the soil. Adult maggot flies emerge from the soil and fly to fruit trees, where they mate on the surface of the fruit. On separate sheet Image Credit Description: Rhagoletis pomonella (male and female apple maggot flies) Source: Author: Jack Kelly Clark Licensing: Photo of Rhagoletis pomonella from UC IPM Pest Management Guidelines: Apple, UC ANR Publication Used with permission from University of California Statewide IPM Program (http://www.ipm.ucdavis.edu).

64 Rhagoletis Host Shift Hybrids are viable and fertile.
Apple-raised Hawthorn-raised Image Credits Description: Rhagoletis on apple Source: Penn State Department of Entomology Image Gallery, Author: Larry Hull Licensing: Images in this gallery have been contributed by individuals committed to the enhancement of teaching and learning. The images may be freely used by faculty, students, and staff for non-commercial educational purposes. Description: Hawthorn fruit Source: UBC Botanical Garden and Centre for Plant Research, Licensing: Licensed under the Creative Commons Attribution-Noncommercial 2.0 Canada License. Description: Red Delicious apple Source: Wikimedia Commons, Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License. Hybrids are viable and fertile. No post-zygotic barriers

65 Rhagoletis Speciation
Hawthorn Apple Small fruit (13 mm) Large fruit (70 mm) High nutritional quality Low nutritional quality Shallow burrows Deep burrows More parasitoid wasps Fewer wasps Fruit available later Fruit available early Image Credits Description: Hawthorn fruit Source: UBC Botanical Garden and Centre for Plant Research, Licensing: Licensed under the Creative Commons Attribution-Noncommercial 2.0 Canada License. Description: Red Delicious apple Source: Wikimedia Commons, Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License.

66 Timing of Host Fruit Ripening
Image Credit Description: Emergence of Rhagoletis pomonella Source: National Center for Case Study Teaching in Science, Author: Jim Stamos, adapted from G. L. Bush, Sympatric host race formation and speciation in frugivorous flies of the genus Rhagoletis (Diptera: Tephritidae), Evolution 23:237–251, 1969. Licensing: Used with permission. Different ripening time of host fruit leads to temporal separation of apple and hawthorn flies.

67 Which information is relevant to the biological species definition
Which information is relevant to the biological species definition? Explain why you chose your answer. Hawthorn and apple maggot flies are physically indistinguishable. There is a 4-6% hybridization rate between hawthorn and apple maggot flies. Hawthorn and apple maggot flies are genetically distinguishable and have a distinct genetic profiles. Hawthorn and apple maggot flies strongly prefer to mate and lay fertilized eggs in hawthorns and apples, respectively.

68 Three outcomes… With renewed or continued contact between two populations, there are three possible outcomes: Individuals can hybridize readily. No speciation 2. Individuals do not hybridize at all. Full speciation 3. Individuals hybridize but offspring have reduced fitness. Speciation in progress. Selection for evolution of strong reproductive barriers.

69 CQ#1: Speciation can only be observed over millions of years:
True False

70 CQ#2: Species are going extinct, but no new species are forming on Earth:
True False

71

72 Q#1: What would the best salmon look like?
Boys: Imagine you are a male salmon. Pick the characteristics you want. Write them down. Girls: Imagine you are a female salmon. Pick the characteristics you want. Write them down. Discussion

73 Q#2 How did you determine what were the best characteristics?
DISCUSSION SLIDE – Write responses on board. Have students indicate agreement/disagreement.

74 Which are the lucky few who make it to reproduce?
SO WHAT WE ARE REALLY TALKING ABOUT IS THE ABILITY TO REPRODUCE

75 The most dominant males (usually largest and most aggressive) successfully defend their redds and inseminate the eggs. Smaller males that also have the kype lose out in head-to-head competition with larger males. Q#3: Are we seeing natural selection in action here? DISCUSSION SLIDE

76 Q#4: Why do these non-dominant males persist in the population over time? Why don’t female mimics get weeded out through natural selection if they are not fit? Using your framework for natural selection, explain why the female mimic phenotype exists.

77 Q#5: Even though female mimics are not dominant, are they fit?
discuss the term fit? Agree that more fit = greater contribution to gene pool

78 Q#6: Given the fitness data, what selection pattern would you expect for the salmon?
Frequency Students should discuss and come up with disruptive selection curve (ideal) Body Size of Salmon

79 Q#7: Do individuals have to be the “strongest” to be fit?
Yes No Discussion. Examples of skin pigmentation; obesity; depression?

80 What selection pattern would you expect for the moths?
Frequency Students should discuss and come up with disruptive selection curve (ideal) Moth Pigmentation

81 Hawthorns Hawthorns are native North American shrubs.
Hawthorn fruits range between 5 mm and 20 mm in diameter, with an average of 12.6 mm. Image Credits Description: Hawthorn tree Source: Wikimedia Commons, Author: Sannse Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License. Description: Hawthorn fruit Source: UBC Botanical Garden and Centre for Plant Research, Licensing: Licensed under the Creative Commons Attribution-Noncommercial 2.0 Canada License.

82 Rhagoletis Host Shift When apples were introduced to North America, the larva of Rhagoletis pomonella started feeding on them. Image Credits Description: Rhagoletis on apple Source: Penn State Department of Entomology Image Gallery, Author: Larry Hull Licensing: Images in this gallery have been contributed by individuals committed to the enhancement of teaching and learning. The images may be freely used by faculty, students, and staff for non-commercial educational purposes. Description: Photo of damaged apple Source: Author: Jack Kelly Clark Licensing: Used with permission from University of California Statewide IPM Program (http://www.ipm.ucdavis.edu).

83 Rhagoletis Speciation
Hawthorn Apple Small fruit (13 mm) Large fruit (70 mm) High nutritional quality Low nutritional quality Shallow burrows Deep burrows More parasitoid wasps Fewer wasps Fruit available later Fruit available early Image Credits Description: Hawthorn fruit Source: UBC Botanical Garden and Centre for Plant Research, Licensing: Licensed under the Creative Commons Attribution-Noncommercial 2.0 Canada License. Description: Red Delicious apple Source: Wikimedia Commons, Licensing: Licensed under the Creative Commons Attribution ShareAlike 3.0 License.

84 Modes of speciation Allopatric speciation is initiated by a geographic barrier between individuals from two natural populations. Sympatric speciation takes place in a single geographic area.


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