1. Speciation occurs when a population diverges into two populations that become reproductively isolated over time, forming new species. 2. There are several modes of speciation including allopatric, peripatric, parapatric, and sympatric speciation. 3. Allopatric speciation involves geographic isolation of populations, often by physical barriers, while other modes like peripatric and sympatric speciation can occur without geographic isolation.

1. Mechanisms of EVOLUTION

3. The formation of a new species
15.3 Speciation

4. What is a
species?
A group of organisms with similar
characteristics capable of
producing fertile offspring

5. Members of a species share the same
gene pool (sum of all the genes + their
different forms – alleles)
What is a
species?

6. New species are formed when a population
diverges into two populations AND
Speciation

7. New species are formed when a population
diverges into two populations AND the
gene pools of two populations become
reproductively isolated
Speciation

8. New species are formed when a population
diverges into two populations AND the
gene pools of two populations become
reproductively isolated = the populations
can’t produce a fertile offsprings
Speciation

9. There are several different ways
speciation can occur...
Speciation

10. Modes of
Speciation
Allopatric Speciation
Peripatric Speciation
Parapatric Speciation
Sympatric Speciation

11. Is a type of geographic isolation
A population is split in two (or more) by some
kind of physical barrier (mountain, river, wall…)
Allopatric Speciation

12. The separated populations undergo changes in
their genes as they begin to adapt to different
environments or as they undergo mutations.
Allopatric Speciation

13. After that time they are no longer
capable of interbreeding (exchanging the
genes)
Allopatric Speciation

14. A population of wild fruit flies minding its
own business on several bunches of rotting
bananas. They also lay eggs inside of
bananas.
EXAMPLE 1 – Allopatric Speciation

15. A hurricane washes the bananas and the
fruit flies’ eggs out to sea. The bananas
eventually wash up on an island off the
coast of the mainland
EXAMPLE 1 – Allopatric Speciation

16. The fruit flies mature (eggs became flies) and
emerge onto the lonely island. The two
portions of the population, mainland and
island, are now too far apart for gene flow to
unite them.
EXAMPLE 1 – Allopatric Speciation

17. At this point, speciation has not occurred
yet — any fruit flies that would fly back
to the mainland could mate and produce
healthy offspring with the mainland
EXAMPLE 1 – Allopatric Speciation

18. The populations diverge: Ecological
conditions are slightly different on the island,
and the island population evolves
differently than the mainland population
EXAMPLE 1 – Allopatric Speciation

19. Morphology (eye color), food preferences,
and mating behaviours change over the
course of many generations of natural
EXAMPLE 1 – Allopatric Speciation

20. When another storm reintroduces the island flies to
the mainland, they will not be able to mate with
the mainland flies since they’ve evolved
different mating behaviours.
EXAMPLE 1 – Allopatric Speciation

21. The flies’ lineages has split now that
genes cannot flow between the
populations
EXAMPLE 1 – Allopatric Speciation

22. Darwin’s Finches
Darwin thought that
a long time ago
there must have
been a common
ancestor to the
finch species.
EXAMPLE 2 – Allopatric Speciation

23. As the Galapagos
islands were formed,
the common
ancestor slowly
dispersed and broke
away from one
another.
Darwin’s Finches
EXAMPLE 2 – Allopatric Speciation

24. Genetic variations
amongst the
finches were then
selected for by the
environment
(natural selection).
Darwin’s Finches
EXAMPLE 2 – Allopatric Speciation

25. This resulted in the
formation of
new species on
each island
Darwin’s Finches
EXAMPLE 2 – Allopatric Speciation

26. Blue headed wrasse and Cortez Rainbow
wrasse
EXAMPLE 3 – Allopatric Speciation

27. Original population was split by the formation of
isthmus of Panama about 3.5 million years ago
Blue headed wrasse and Cortez Rainbow
wrasse
EXAMPLE 3 – Allopatric Speciation

28. Since that time, genetic changes happened in the both
populations. These changes led to creation of
different species
Blue headed wrasse and Cortez Rainbow
wrasse
EXAMPLE 3 – Allopatric Speciation

29. Hawaiian honeycreepers
Very similar to Galapagos’ finches
EXAMPLE 4 – Allopatric Speciation

30. On each island of Hawaii, we can find different
species of honeycreeper
Hawaiian honeycreepers
EXAMPLE 4 – Allopatric Speciation

31. It is thought that they all descended from a single
species of honeycreeper
Hawaiian honeycreepers
EXAMPLE 4 – Allopatric Speciation

32. Hawaiian honeycreepers
EXAMPLE 4 – Allopatric Speciation

33. a special version of the allopatric speciation
- It happens when one of the isolated populations
has very few individuals
- genetic drift (the founder effect) plays a major
role in this speciation
Peripatric Speciation

34. A population of wild fruit flies minding its own business
on several bunches of rotting bananas also laying
eggs inside of bananas.
Peripatric Speciation

35. A hurricane washes the bananas and the fruit flies’
eggs out to sea. The bananas eventually wash up on
an island off the coast of the mainland
Peripatric Speciation

36. But only a few eggs have survived the journey to end
up colonizing the island.
Peripatric Speciation

37. These few survivors just by chance carry some genes
that are very rare in the mainland population.
Peripatric Speciation

38. One of these rare genes causes a slight variation in the
mating behaviour and changes in sexual organs.
(REMEMBER? it’s an example of the founder effect)
Peripatric Speciation

39. After a few generations, the entire island population
ends up having these rare genes.
Peripatric Speciation

40. As the island population grows, flies experience
natural selection that favours individuals better
suited to the reproductive behaviour, climate and
food of the island.
Peripatric Speciation

41. After some generations, the island flies become
isolated from the mainland flies.
Peripatric speciation has occurred
Peripatric Speciation

42. Peripatric vs Allopatric
Speciation
WHAT IS THE DIFFERENCE
BETWEEN THEM?

43. Peripatric vs Allopatric
Speciation
It is the size of the
populations involved!

44. In allopatric speciation, a population is separated into
two relatively large independent populations.
In peripatric speciation, only a small fraction of the
original population becomes geographically isolated.
Peripatric vs Allopatric
Speciation

45. There is no specific barrier (mountain, river…) to
gene flow, but the population does not mate
randomly
Parapatric Speciation

46. Individuals are more likely to mate with their
geographic neighbours than with individuals in a
different part of the population’s area
Parapatric Speciation

47. The two species may come in contact from time to time
but (after some time), species can no longer produce
offspring together anymore
Parapatric Speciation

48. A grass species
Anthoxanthum odoratum
EXAMPLE 1 – parapatric Speciation

49. Some of these plants live near mines where the soil has
become contaminated with heavy metals.
EXAMPLE 1 – parapatric Speciation

50. Some plants around the mines have experienced
natural selection and are now tolerant of heavy
metals.
EXAMPLE 1 – parapatric Speciation

51. The neighbouring plants that don’t live in polluted soil
have not experienced natural selection for this trait
(they have NO tolerance of heavy metals)
EXAMPLE 1 – parapatric Speciation

52. Both plants are close enough that they could fertilize
each other (mate with each other)
EXAMPLE 1 – parapatric Speciation

53. However, the two types of plants have evolved different
flowering times. This change is the first step in cutting
off gene flow between the two groups = SPECIATION
EXAMPLE 1 – parapatric Speciation

54. In sympatric speciation, species diverge while
inhabiting the same place.
Sympatric Speciation

55. It does not require large area to reduce gene flow
between parts of a population
Sympatric Speciation

56. 200 years ago, the ancestors of apple maggot flies laid
their eggs only on hawthorns
Maggots Hawthorns
Example of Sympatric Speciation

57. but today, these flies lay eggs on
hawthorns and domestic apples (which
were introduced to America by
immigrants)
Example of Sympatric Speciation
Maggots
Hawthorns
Apples

58. Females generally choose to lay their eggs on the type
of fruit they grew up in, and males tend to look for
mates on the type of fruit they grew up in.
Example of Sympatric Speciation

59. So hawthorn flies generally end up mating
with other hawthorn flies
+
Hawthorns
Hawthorns
Example of Sympatric Speciation

60. and apple flies generally end up mating
with other apple flies.
+
Example of Sympatric Speciation
Apples
Apples

61. Hawthorn flies and
apple flies never mate
together
+
Hawthorns Apples
Example of Sympatric Speciation

62. This means that gene flow between parts
of the population that mate on different
types of fruit is reduced.
+
Hawthorns Apples
Example of Sympatric Speciation

63. This host shift from hawthorns to apples may
be the first step toward sympatric speciation
—in fewer than 200 years, some genetic
differences between these two groups of flies
have evolved
+
Hawthorns Apples
Example of Sympatric Speciation

65. Speciation is a long process, but we can find
evidence for it in PATTERNS OF EVOLUTION
Evidence for
Speciation?

66. Adaptive radiation
PATTERNS OF EVOLUTION
Coevolution
Convergent Evolution Rate of Speciation

68. Coevolution
• Many species evolve in close relationship with
other species.

69. Coevolution
• The relationship might be so close that the
evolution of one species affects the evolution
of other species. This is called coevolution.
• For Example: Mutualism - when two species
benefit each other.

70. Coevolution – EXAMPLE
• comet orchids and the moths that pollinate them have
coevolved an intimate dependency
• the foot long flowers of this plant perfectly match the
foot-long tongue of the moth

71. Coevolution – EXAMPLE
• A plant and an insect that is dependent on the plant for
food.
– The plant population evolves a chemical defense against the
insect population.
– The insects, in turn, evolve the biochemistry to resist the defense.
– The plant then steps up the race by evolving new defences, the
insect escalates its response, and the race goes on.

72. Adaptive Radiation = divergent evolution
• can occur in a relatively short time when one species
gives rise to many species in response to the creation of
new habitat or another ecological opportunity.

73. Adaptive Radiation = divergent evolution
• Adaptive radiation often follows large - scale extinctions
(such as the extinction of dinosaurs and subsequent rise
of mammals)
• These different species have homologous structures

74. Adaptive Radiation – EXAMPLE 1
• More than 300 species of cichlid fish once lived in Africa’s
Lake Victoria.
• Data shows that these species diverged from a single
ancestor within the last 14,000 years.

75. Produces
Homologous
Structures
Adaptive Radiation = divergent evolution

76. common adaptations to similar
environments
Convergent Evolution

77. occurs when
organisms that
are NOT closely
related (they have
no common
ancestors) live in
the SAME
environment in
different parts of
the world.
Convergent Evolution

78. • all of these animals live or lived in an ocean but
they are not closely related
Convergent Evolution – Example 1

79. These species independently evolved similar traits or
structures which are adapted to that same environment
What similar traits or structures these three
animals gained during the course of
evolution?
Convergent Evolution

80. Flippers, streamlined body, ability to swim
What similar traits or structures these three
animals gained during the course of
evolution?
Convergent Evolution

81. Convergent Evolution
Prickles, thorns and spines

82. They have evolved independently
to prevent or reduce herbivory
(eating of plants by organisms)
Convergent Evolution

83. Produces
Analogous
Structures
Convergent Evolution

84. Produces
Homologous
Structures
Adaptive Radiation = divergent evolution

85. Analogues Structures
Homologues Structures
VS.

86. Analogues
Structures
Homologues
Structures
VS.
Different internal
structures
Same Function
Similar Environments
Result of Convergent
Evolution
Same internal structures
Different Functions
Different Environments
Result of Divergent
Evolution