Heliconius butterflies
Real Example: Reproductive isolation + Sexual Selection
+ Natural Selection = sympatric species
• l...
Heliconius butterflies
Real Example: Reproductive isolation + Sexual Selection
+ Natural Selection = sympatric species
• l...
1) Why aren’t hybrids more common?
2) How do overlapping (sympatric) species remain distinct species?
Real Example: Reprod...
Experiment
Real Example: Reproductive isolation + Sexual Selection
+ Natural Selection
• Mating confirmed by identifying m...
Real Example: Reproductive isolation + Sexual Selection
+ Natural Selection
Results: Assortative mating in both species an...
Results: Sexual Selection against hybrids because they don’t have
attractive traits (in this case color pattern)
Real Exam...
Results: Natural Selection: hybrids eaten by Jacamar birds
(and other predators) more than parent species are.
Real Exampl...
Results: Natural Selection: hybrids eaten by Jacamar birds
(and other predators) more than parent species are.
Real Exampl...
Darwin & The Modern Synthesis (Natural
Selection, Heredity & Genetics)
• Speciation was introduced by Darwin, in On the
Or...
Darwin & The Modern Synthesis (Natural
Selection, Heredity & Genetics)
•Allopatric speciation: evolution of reproductive
i...
Allopatric speciation: - requires geographic separation.
- Most documented kind of speciation
In this model, speciation re...
Allopatric speciation: - requires geographic separation.
- Most documented kind of speciation
In this model, speciation re...
Allopatric speciation: - requires geographic separation.
- Most documented kind of speciation
Secondary contact: occurs af...
Allopatric speciation: - requires geographic separation,
Geographic separation of one population into two occurs by:
(A) v...
Allopatric Speciation
Allopatric speciation: - requires geographic separation,
Geographic separation of one population int...
Allopatric speciation: - requires geographic separation, which
causes reproductive isolation.
Geographic separation of one...
Initially, there is migration between 2 nearby populations of a
forest-dwelling animal with two alleles controlling color
...
Over time, a barrier to migration arises between populations:
mountain range
The allele frequencies in each population wil...
The populations will slowly diverge as different alleles become
fixed at many loci throughout the genome
(Step 2: populati...
(Step 3: the populations become reproductively isolated)
mountain range
Differences accumulate BY CHANCE in alleles
contro...
... but because of assortative mating, the two types do not interbreed
have formed sister species that will now evolve sep...
Consider a species found in a desert and a neighboring forest
Hot, dry
desert
Cool,
rainy
forest
Allopatric speciation : V...
Selection will favor different alleles in the desert and forest
Hot, dry
desert
Cool,
rainy
forest
Natural selection will ...
After selection, the two populations will be genetically different
Hot, dry
desert
Cool,
rainy
forest
forest-adapted indiv...
However, migration will keep mixing alleles between the populations
Hot, dry
desert
Cool,
rainy
forest
Allopatric speciati...
Now: a barrier to gene flow arises between the 2 habitats
Hot, dry
desert
Cool,
rainy
forest
mountains
Allopatric speciati...
Now: a barrier to gene flow arises between the 2 habitats
Hot, dry
desert
Cool,
rainy
forest
Natural selection will favor
...
Each population evolves into a distinct, well-adapted species
Hot, dry
desert
Cool,
rainy
forest
Forest-adapted population...
Hawaiian Drosophila
Allopatric speciation : Dispersal & founders
Speciation and the Isthmus of Panama
RESULTS of mating experiments:
(1) Sister-species shrimp snapped at each other instea...
Caribbean and Pacific oceans were linked until the Isthmus
of Panama formed ~3.5 million years ago
Prevented any more
gene...
Speciation and the Isthmus of Panama
Knowlton et al. studied pairs of snapping shrimps that were
morphologically similar, ...
Knowlton & Weigt 1998
• based on DNA sequences, the
members of each pair were
indeed each other’s closest
relatives
- That...
What is a species?
• Species are the fundamental units of
biodiversity
• Note: one species, two species
http://carabidae.p...
Importance of recognizing species
• Survival depends on our ability to recognize species
What is a species?
Universality of recognizing species
What is a species?Time
Amount of divergence (morphology)
What is a species?
• Races
• Varieties
• “kinds”
• Incipient species
• Ecotypes
• Morphs
• Subspecies
• Cultivars (Artific...
Time
Amount of divergence
What is a species?
What is a species?
What is a species?
1) speciation by
cladogenesis
2) speciation by
anagenesis between a & b
a
b
anagenesis
Anagenesis: no cladogenesis
cladogenesis
Cladogenesis: speciation
Anagenesis + Cladogenesis
A B C D E
A
B
C
D
Most of the time we don’t
know the ancestral states for
sure
What is a species?
• Biologists do not agree on ONE way to
define a species – thus, “species concepts”
Why?
At least 22 different definitions have been proposed to
explain what a “species” is.
Three main ones:
1. Morphological
2. ...
Morphological species concept
: Two organisms that display “substantial”
and consistent morphological differences
are diff...
Morphological species concept
: Chronospecies: a morphology that can be
identified as a stage in an evolving lineage
(anag...
Biological species concept
: a group of actually or potentially inter-
breeding individuals
• Advantages: testable in many...
Fertile Hybrids:
Violations of both the Morphological v. Biological species
Concepts
Phylogenetic species concept
: Lineages with different evolutionary histories
are different species – these lineages must ...
Phylogenetic species concept
: Lineages with different evolutionary histories
are different species – these lineages must ...
Phylogenetic species concept
Issues & Solutions
Issue: How genetically different do species have to be?
Solutions:
- from a single DNA base change that...
High level of cryptic species
diversity revealed by sympatric
lineages of Southeast Asian
forest frogs
Bryan L Stuart, Rob...
High level of cryptic species
diversity revealed by sympatric
lineages of Southeast Asian
forest frogs
Bryan L Stuart, Rob...
High level of cryptic species
diversity revealed by sympatric
lineages of Southeast Asian
forest frogs
Bryan L Stuart, Rob...
Rana chalconota
cf. = similar to
Cryptic species
by the phylogenetic species concept
Cryptic species
by the phylogenetic species concept
Morphology + DNA
Forest habitat Savanna habitat
Cryptic species
by the phylogenetic species concept
LoxodontiaafricanaElephas
maximus
Cryptic species
by the phylogenetic species concept + extinct organisms!
6 mya
Ring species
by the phylogenetic & morphological & biological species concepts
Ring species
by the phylogenetic & morphological & biological species concepts
How do you describe a species?
1. Compare it to all similar described species
2. Name it
• Must be latinized & binominal
3...
Bio413 07 sympatric_speciation_species concepts_allopatric_speciation_winter2012_posted
Bio413 07 sympatric_speciation_species concepts_allopatric_speciation_winter2012_posted
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  • Seasonal/temporal isolation: timing of gamete release (sperm and eggs don’t meet)
  • Seasonal/temporal isolation: timing of gamete release (sperm and eggs don’t meet)
  • Seasonal/temporal isolation: timing of gamete release (sperm and eggs don’t meet)
  • Seasonal/temporal isolation: timing of gamete release (sperm and eggs don’t meet)
  • Seasonal/temporal isolation: timing of gamete release (sperm and eggs don’t meet)
  • Seasonal/temporal isolation: timing of gamete release (sperm and eggs don’t meet)
  • The model of allopatric speciation says nothing more is needed
    for 2 populations to evolve into separate species but
    geographical isolation + time
    - this remains the dominant view of how most speciation has
    taken place over earth’s history
    - notice: there is no requirement for natural selection to
    play a role in species formation
    Because drift is a random process, it may take a very long time
    for enough fixed differences to build up to prevent two
    populations from interbreeding
    - according to this model, species should only co-exist if
    they were 1st isolated from each other for a long time
  • As these photos of Drosophila suzukii, D. macrothrix, and D. nigribasis (top to bottom) show, the Drosophila found in Hawaii are remarkably diverse in body size, wing coloration, and other traits.
  • All human cultures recognize and name species. Because we eat other species of living organisms it is very important that we can properly recognize species with different characteristics and that we have names for them, so we can communicate about the characteristics of the different species.
  • A wholphin or wolphin is a rare hybrid, born from a mating of bottlenose dolphin. Polar-Grizzly Bear Hybrid. An example of a sheep-goat chimera. A Cama is a hybrid between a camel and a llama. A jaglion, Jaguar-Lion Hybrid. Würdemann's Heron, a great blue heron white egret hybrid.
  • The taxa labeled A-G on the tips of this phylogeny represent distinct species. Groups labeled G1, G2 etc. represent populations of the same species.
  • In West Africa, elephants that live in forest habitats (left) have morphological characteristics that distinguish them from savanna-dwelling elephants (right) from west, central, and east Africa.
  • This evolutionary tree indicates that forest-dwelling elephants are a distinct phylogenetic species.
  • Bio413 07 sympatric_speciation_species concepts_allopatric_speciation_winter2012_posted

    1. 1. Heliconius butterflies Real Example: Reproductive isolation + Sexual Selection + Natural Selection = sympatric species • live in various habitats in South America • Müllerian mimics to other Heliconius species in or close to their range, all are unpalatable (taste bad to predators)
    2. 2. Heliconius butterflies Real Example: Reproductive isolation + Sexual Selection + Natural Selection = sympatric species • live in various habitats in South America • Müllerian mimics to other Heliconius species, all unpalatable (taste bad to predators) • (incomplete) pre-zygotic isolation by habitat isolation H. cydno: live in forest understory H. melpomene: live in disturbed re-growth forest Species overlap in intermediate habitats and found flying together: rare hybrids found in wild
    3. 3. 1) Why aren’t hybrids more common? 2) How do overlapping (sympatric) species remain distinct species? Real Example: Reproductive isolation + Sexual Selection + Natural Selection
    4. 4. Experiment Real Example: Reproductive isolation + Sexual Selection + Natural Selection • Mating confirmed by identifying male spermatophore in female via dissection • Mate choice (and sexual selection pressure) is by MALES (male choice) & based on female color pattern • A male mates with a newly hatched female before her first flight • Males and females exposed to each other in no-choice trials (1 hr)
    5. 5. Real Example: Reproductive isolation + Sexual Selection + Natural Selection Results: Assortative mating in both species and their hybrid Males prefer to mate with females of their “type”
    6. 6. Results: Sexual Selection against hybrids because they don’t have attractive traits (in this case color pattern) Real Example: Reproductive isolation + Sexual Selection + Natural Selection Hybrids females are mated with 50% less often by males of either “parent” species
    7. 7. Results: Natural Selection: hybrids eaten by Jacamar birds (and other predators) more than parent species are. Real Example: Reproductive isolation + Sexual Selection + Natural Selection Hybrids aren’t protected from predators by Müllerian mimicry, thus more eaten by predators (N.S) =
    8. 8. Results: Natural Selection: hybrids eaten by Jacamar birds (and other predators) more than parent species are. Real Example: Reproductive isolation + Sexual Selection + Natural Selection Hybrids are eaten more by predators. The parent species are favored by N.S.: Disruptive selection
    9. 9. Darwin & The Modern Synthesis (Natural Selection, Heredity & Genetics) • Speciation was introduced by Darwin, in On the Origin of Species by Natural Selection (1859) • Darwin didn’t discuss allopatric speciation or genetic drift • The Modern Synthesis focused on geographical isolation and genetic drift (isolation + time ) Allopatric speciation =
    10. 10. Darwin & The Modern Synthesis (Natural Selection, Heredity & Genetics) •Allopatric speciation: evolution of reproductive isolation and divergence between populations that are geographically separate
    11. 11. Allopatric speciation: - requires geographic separation. - Most documented kind of speciation In this model, speciation results from differences in mating preference that arise from 2 possible sources: (1) genetic drift: Allopatric Speciation http://evolution.berkeley.edu/evosite/evo101/IIIDGeneticdrift.shtml
    12. 12. Allopatric speciation: - requires geographic separation. - Most documented kind of speciation In this model, speciation results from differences in mating preference that arise from 2 possible sources: (1) genetic drift: Change in allele frequencies due to chance. (2) disruptive selection: Natural Selection and/or Sexual Selection that favors more extreme phenotypes over the original average phenotype Allopatric Speciation
    13. 13. Allopatric speciation: - requires geographic separation. - Most documented kind of speciation Secondary contact: occurs after evolving in isolation, two populations come back into contact with each other •If the divergence is recent, these two species (or populations) may hybridize producing fertile offspring •If the divergence is substantial, the two species may hybridize producing unfertile offspring or may not hybridize at all Allopatric Speciation
    14. 14. Allopatric speciation: - requires geographic separation, Geographic separation of one population into two occurs by: (A) vicariance –separation of a population by geological forces Allopatric Speciation
    15. 15. Allopatric Speciation Allopatric speciation: - requires geographic separation, Geographic separation of one population into two occurs by: (A) vicariance –separation of a population by geological forces Examples: - a new river, glacier, or mountain range forms - a land bridge forms or is submerged - plate tectonics and continent movements
    16. 16. Allopatric speciation: - requires geographic separation, which causes reproductive isolation. Geographic separation of one population into two occurs by: (B) dispersal - colonization of a new habitat by founders Examples: - islands - postglacial lakes (Canada), rift lakes (Africa) Allopatric Speciation
    17. 17. Initially, there is migration between 2 nearby populations of a forest-dwelling animal with two alleles controlling color Allopatric speciation : Vicariance + Genetic drift because of gene flow, the allele frequencies will be the same in the two populations
    18. 18. Over time, a barrier to migration arises between populations: mountain range The allele frequencies in each population will start to change due to genetic drift (Step 1: gene flow has been interrupted) Allopatric speciation : Vicariance + Genetic drift
    19. 19. The populations will slowly diverge as different alleles become fixed at many loci throughout the genome (Step 2: populations differentiate) mountain range Different alleles may eventually fix in the 2 populations Allopatric speciation : Vicariance + Genetic drift
    20. 20. (Step 3: the populations become reproductively isolated) mountain range Differences accumulate BY CHANCE in alleles controlling mate preference: mating signals, genital shapes, etc. Allopatric speciation : Vicariance + Genetic drift
    21. 21. ... but because of assortative mating, the two types do not interbreed have formed sister species that will now evolve separately If the mountain range disappears, the two populations can mix = Secondary Contact. (Step 4: speciation has occurred) Allopatric speciation : Vicariance + Genetic drift
    22. 22. Consider a species found in a desert and a neighboring forest Hot, dry desert Cool, rainy forest Allopatric speciation : Vicariance + Disruptive Selection
    23. 23. Selection will favor different alleles in the desert and forest Hot, dry desert Cool, rainy forest Natural selection will favor forest-adapted individuals Natural selection will favor desert-adapted individuals Allopatric speciation : Vicariance + Disruptive Selection
    24. 24. After selection, the two populations will be genetically different Hot, dry desert Cool, rainy forest forest-adapted individuals have survived here desert-adapted individuals have survived here Allopatric speciation : Vicariance + Disruptive Selection
    25. 25. However, migration will keep mixing alleles between the populations Hot, dry desert Cool, rainy forest Allopatric speciation : Vicariance + Disruptive Selection Maybe some evolution, but NO SPECIATION unless there is reproductive isolation
    26. 26. Now: a barrier to gene flow arises between the 2 habitats Hot, dry desert Cool, rainy forest mountains Allopatric speciation : Vicariance + Disruptive Selection
    27. 27. Now: a barrier to gene flow arises between the 2 habitats Hot, dry desert Cool, rainy forest Natural selection will favor forest-adapted individuals Natural selection will favor desert-adapted individuals mountains Allopatric speciation : Vicariance + Disruptive Selection
    28. 28. Each population evolves into a distinct, well-adapted species Hot, dry desert Cool, rainy forest Forest-adapted population Desert-adapted population mountains Species #1 Species #2 Allopatric speciation : Vicariance + Disruptive Selection No migration
    29. 29. Hawaiian Drosophila Allopatric speciation : Dispersal & founders
    30. 30. Speciation and the Isthmus of Panama RESULTS of mating experiments: (1) Sister-species shrimp snapped at each other instead of mating! This is pre-zygotic reproductive isolation (sexual isolation): mating signals not understood by potential mates (2) when a male of one species was held with a female of its sister species [from the other side of Panama] for a month, no offspring were produced except for one single pair This is either pre-zygotic isolation (gamete isolation) or post-zygotic reproductive isolation: zygote does not develop. For snapping shrimp: 3.5 million years is enough time for complete reproductive isolation to occur Allopatric speciation: Vicariance
    31. 31. Caribbean and Pacific oceans were linked until the Isthmus of Panama formed ~3.5 million years ago Prevented any more gene flow between marine organisms on each side of the new land barrier Did this result in the evolution of new sister species pairs separated by the Isthmus? Speciation and the Isthmus of Panama Google maps Allopatric speciation : Vicariance
    32. 32. Speciation and the Isthmus of Panama Knowlton et al. studied pairs of snapping shrimps that were morphologically similar, where one member of the pair was found on the Caribbean side and the other on the Pacific side Knowlton & Weight 1998 Alphaeus cylindricus The sister species still closely resembled each other – were they different species? Sequenced part of a gene and also compared allele frequencies Finally, did mating crosses to assess reproductive compatibility would shrimp mate or fight with their sister species? Allopatric speciation : Vicariance
    33. 33. Knowlton & Weigt 1998 • based on DNA sequences, the members of each pair were indeed each other’s closest relatives - That is, each sister-group pair were were descendants of a common ancestor Allopatric speciation: Vicariance
    34. 34. What is a species? • Species are the fundamental units of biodiversity • Note: one species, two species http://carabidae.pro/carabidae/elaphrinae.html Elaphrus beetles
    35. 35. Importance of recognizing species • Survival depends on our ability to recognize species What is a species?
    36. 36. Universality of recognizing species
    37. 37. What is a species?Time Amount of divergence (morphology)
    38. 38. What is a species? • Races • Varieties • “kinds” • Incipient species • Ecotypes • Morphs • Subspecies • Cultivars (Artificial Selection) • Breeds (Artificial Selection)
    39. 39. Time Amount of divergence What is a species?
    40. 40. What is a species?
    41. 41. What is a species? 1) speciation by cladogenesis 2) speciation by anagenesis between a & b a b
    42. 42. anagenesis Anagenesis: no cladogenesis
    43. 43. cladogenesis Cladogenesis: speciation
    44. 44. Anagenesis + Cladogenesis A B C D E A B C D Most of the time we don’t know the ancestral states for sure
    45. 45. What is a species? • Biologists do not agree on ONE way to define a species – thus, “species concepts” Why?
    46. 46. At least 22 different definitions have been proposed to explain what a “species” is. Three main ones: 1. Morphological 2. Biological 3. Phylogenetic Species concepts
    47. 47. Morphological species concept : Two organisms that display “substantial” and consistent morphological differences are different species • Advantages: Easy to apply, can be used with fossil species – Disadvantages: It is not testable, the definition of “substantial” is subjective. Problems with convergence, cryptic species, hybridization (= gene flow) & intermediate phenotype
    48. 48. Morphological species concept : Chronospecies: a morphology that can be identified as a stage in an evolving lineage (anagenesis) Note increasing number of pleura (or “ribs”) on trilobites
    49. 49. Biological species concept : a group of actually or potentially inter- breeding individuals • Advantages: testable in many cases, objective • Disadvantages: difficult to apply and test (impractical), cannot be used with fossils, irrelevant to asexual populations
    50. 50. Fertile Hybrids: Violations of both the Morphological v. Biological species Concepts
    51. 51. Phylogenetic species concept : Lineages with different evolutionary histories are different species – these lineages must be the smallest units of evolution • Advantage: it is testable, objective and can be applied to living and fossil species – Disadvantage: it requires comprehensive phylogenetic analyses = need a cladogram!
    52. 52. Phylogenetic species concept : Lineages with different evolutionary histories are different species – these lineages must be the smallest units of evolution •Instead of depending on reproductive isolation, this concept revolves around fixed differences between populations •Species are the smallest population that you don’t have any reason to divide into even smaller clades or populations
    53. 53. Phylogenetic species concept
    54. 54. Issues & Solutions Issue: How genetically different do species have to be? Solutions: - from a single DNA base change that only exists in one population, to many consistent genetic differences across genes, also consistent measurable phenotypic differences - Ideally, multiple fixed differences should be used - Need a well-supported cladogram. Phylogenetic Species Concept
    55. 55. High level of cryptic species diversity revealed by sympatric lineages of Southeast Asian forest frogs Bryan L Stuart, Robert F Inger, and Harold K Voris Biol Lett. 2006 September 22; 2(3): 470–474. Odorrana livida Cryptic species by the phylogenetic species concept cf. = similar to
    56. 56. High level of cryptic species diversity revealed by sympatric lineages of Southeast Asian forest frogs Bryan L Stuart, Robert F Inger, and Harold K Voris Biol Lett. 2006 September 22; 2(3): 470–474. Odorrana livida Cryptic species by the phylogenetic species concept Cryptic species: organisms that appear identical or almost identical to close relatives, but are genetically distinct- they are their own lineage Odorrana livida
    57. 57. High level of cryptic species diversity revealed by sympatric lineages of Southeast Asian forest frogs Bryan L Stuart, Robert F Inger, and Harold K Voris Biol Lett. 2006 September 22; 2(3): 470–474. Odorrana livida Cryptic species by the phylogenetic species concept cf. = similar to Odorrana livida
    58. 58. Rana chalconota cf. = similar to Cryptic species by the phylogenetic species concept
    59. 59. Cryptic species by the phylogenetic species concept Morphology + DNA Forest habitat Savanna habitat
    60. 60. Cryptic species by the phylogenetic species concept LoxodontiaafricanaElephas maximus
    61. 61. Cryptic species by the phylogenetic species concept + extinct organisms! 6 mya
    62. 62. Ring species by the phylogenetic & morphological & biological species concepts
    63. 63. Ring species by the phylogenetic & morphological & biological species concepts
    64. 64. How do you describe a species? 1. Compare it to all similar described species 2. Name it • Must be latinized & binominal 3. Designate a type • Designate a holotype • Designate paratypes (if possible) 4. Describe it 5. Provide a picture or illustration 6. Designate a type locality 7. Deposit it (the type or types) into a museum 8. Publish the description in a peer-reviewed journal
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