Download Parallel Evolution

8.8 / 8.9 magnitude
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5/3/2017
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Tsunami strikes Japan - 10-meter high
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Tsunami strikes Japan
Hawaii orders evacuation of low-lying coastal
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triggered tsunami alert
Tsunami warning for all the Pacific!
5/3/2017
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Tsunami warnings…
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Let’s review: Natural Diversity
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By the Numbers –
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Estimated 2 - 100 million species, with a best estimate of
somewhere near 10 million
~1.4 million described species
~1 million described insects/ 350,000 described beetles
8,800–10,200 living bird species
~5,500 species of mammals
Great diversity exists, with each species exhibiting a
considerable degree of suitability for its natural
lifestyle
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How?
Seems unlikely
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What is evolution?

Broad: The gradual process by which the
living world has been developing following
the origin of life.

Narrow: Change in the genetic frequencies of
a population.
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Why is the theory of evolution important?

Implications for people:
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Antibiotic resistance, pesticide resistance, control
of disease, human epidemiology, development of
new crops, medical treatments, conservation
biology, etc. (not to mention the ecological
implications)
Evolution provides the mechanism to address
these issues.
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Evidence for evolution

Fossil Record (The fossil record provides snapshots of the past that,
when assembled, illustrate a panorama of evolutionary change over the past four
billion years. The picture may be smudged in places and may have bits missing, but
fossil evidence clearly shows that life is old and has changed over time.)
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Morphology
Vestigial organs (A vestigial organ or structure is any organ or
structure found in a species which is not being used as it is in other species.
Contrary to popular belief, vestigial organs and vestigial structures aren't
necessarily useless or functionless.)
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Biogeography (study of the distribution of species (biology) spatially
(geography) and temporally (history).)
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Molecular evidence (All living things are fundamentally alike. At the
cellular and molecular level living things are remarkably similar to each other. These
fundamental similarities are most easily explained by evolutionary theory: life shares
a common ancestor. )
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Early fossil discoveries
In the 17th century, Nicholas Steno: similarity
between shark teeth and the rocks commonly
known as "tongue stones".
- first understanding that fossils were a record
of past life.
Two centuries later, Mary Ann Mantell picked
up a tooth, which her husband Gideon thought
to be of a large iguana, but it turned out to be
the tooth of a dinosaur, Iguanodon.
- many fossils represented forms of life that are
no longer with us today.
Nicholas Steno's anatomical
drawing of an extant shark and
a fossil shark tooth. Nicholas
Steno's anatomical drawing of
an extant shark (left) and a
fossil shark tooth (right). Steno
made the leap and declared
that the fossil teeth indeed
came from the mouths of once
living sharks.
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Transitional forms
Pakicetus is described as an early ancestor
to modern whales. Although pakicetids were
land mammals, it is clear that they are
related to whales and dolphins based on a
number of specializations of the ear, relating
to hearing. The skull shown here displays
nostrils at the front of the skull.
A skull of the gray whale that roams the
seas today has its nostrils placed at
the top of its skull. It would appear
from these two specimens that the
position of the nostril has changed
over time and thus we would expect
to see intermediate forms.
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Evidence for evolution: Fossil record
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Evidence for evolution: Fossil record
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Jaw bone
evolution from
therapsid reptiles
to mammals.
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Evidence for evolution: Fossil record
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Evolution through time:
Variation through geologic periods.
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Fossils in most recent strata are often similar if not
indistinguishable from living species.
The older the strata is, the more different the
fossils.
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Evidence for evolution

Morphology:
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This was how
species were
described as
“related” as far back
as 18th century.
Linnaean hierarchy:
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From Kingdom to
sub-species
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Evidence for evolution
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Vestigial Structures:
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Structures that are not fully functional or functional
at all.
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Evidence for evolution
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Vestigial Structures
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Blind cave dwelling animals still have eyes (that
don’t work).
Why does an ostrich have wings?
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Evidence for evolution: Biogeography
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Biogeography:
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the geographic
distribution of
organisms
those [organisms]
of the Cape de
Verde Islands
bearing the
impress of Africa,
as the inhabitants
of the Galapagos
Archipelago are
stamped with that
of America.
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Evidence for evolution: Biogeography

Evolution through space:
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Gondwana
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Evolution through time and space
EFFECTS OF CONTINENTAL
DRIFT ON ECOLOGY OF
EVOLUTION
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The history of life can be gauged by the geological time
scale.
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Ecologists recognize key features of the
geological record:
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earth formed 4.5 billion years ago
life arose within the first billion years
life remained primitive for most of earth’s history
ancient physical environments were quite different
from those of the present:
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the early atmosphere had little oxygen and early microbes
used anaerobic metabolism
increased oxygen led to diversification of complex life forms
The Geologic Record
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About 590 Mya, most of the modern phyla of
invertebrates appeared in the fossil record:
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these early animals began to protect themselves with
hard shells, which make excellent fossils
the Paleozoic era is thus the first of three major
divisions of geologic time reflecting diversification of
animals:
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Paleozoic: 590 Mya to 248 Mya
Mesozoic: 248 Mya to 65 Mya
Cenozoic: 65 Mya to present
Continental Drift
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The continents are islands of low-density rock
floating on the denser material of the earth’s
interior and carried along by convection currents:
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the movements of the continents over time are called
continental drift
These movements have two important ecological
consequences:
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positions of continents, ocean basins influence climate
continental drift creates and breaks barriers to dispersal
Continental Drift: Mesozoic to Present
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In the early Mesozoic era, 200 Mya, continents
formed a single giant landmass called Pangaea
By 144 Mya (beginning of the Cretaceous
period) the northern continents (Laurasia) had
separated from the southern continents
(Gondwana)
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at this time Gondwana itself was also breaking apart
By the end of the Mesozoic era (65 Mya), South
America and Africa were widely separated, and
many other patterns were emerging.
Continental drift
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Consequences of Continental Drift
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Details of continental drift have yet to be
resolved, but implications for evolution of
animals and plants are clear; for example:
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the distributions of the flightless ratite birds (such as
ostriches) are the results of connection between the
southern continents that made up Gondwana:
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these birds are descended from a common Gondwanan
ancestor
splitting of a widely distributed ancestral population by
continental drift is called vicariance
Lineages of ratite birds were separated by the fragmentation of Gondwana – 80
mya. Evolutionary relationships of these birds reconstructed from DNA sequences
(A) Large
flightless
birds
(B) the
phylogenetic
tree of the
flightles
birds
(C) Ostrich (left)
is African;
rhea
(middle) is
found in
similar
grasslands in
South
America; the
emu (right) in
Australia
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Analogous: similar in superficial form or function
Homologous: derived from an equivalent structure in a common
ancestry
EVOLUTION: CONVERGENT
AND PARALLELS
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Convergence
Convergence is the process whereby unrelated
species living under similar ecological conditions
come to resemble one another more than their
ancestors did:
 Analagous but not homologous
 there are numerous examples of convergence:
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woodpecker-like birds that fill the woodpecker
niche in many systems lacking woodpeckers
similarities of plants and animals of North and
South American deserts
similar body forms of dolphins and penguins, which
both resemble tuna, whose swimming lifestyle they
share
Convergent evolution
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Wings of bats and birds – similar in
form/function but not from a common
ancestry; structurally different
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Pairs of unrelated
African and South
American rain forest
mammals: similar
lifestyles and
adaptations; striking
convergence
Parallel evolution
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Ancestrally related groups – then isolated
from each other
In contrast to convergent evolution,
diversified from a common ancestral line and
both inherited a common set of potentials
and constraints
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Parallel
evolution of
marsupial and
placental
mammals:
Pairs of species
are similar in
both
appearance
and habit and
usually (not
always) in
lifestyle
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To recap
Convergent Evolution
 Convergent evolution takes place when
species of different ancestry begin to
share analogous traits because of a
shared environment or other selection
pressure. For example, whales and fish
have some similar characteristics since
both had to evolve methods of moving
through the same medium: water.
Parallel Evolution
 Parallel evolution occurs when two
species evolve independently of each
other, maintaining the same level of
similarity. Parallel evolution usually
occurs between unrelated species that
do not occupy the same or similar
niches in a given habitat.
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
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(a) divergent
(b) convergent
(c) parallel
Evidence for evolution
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Molecular evidence
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the more closely related two organisms are, the
more similar are their genetic structure.
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Often times, morphological traits can be
ambiguous.
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One of the most important sources of information
on phylogenetic relationships
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Maintaining Genetic Variation –
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Without Selection: no loss or gain (random)
B. Hardy-Weinberg Theorem: constant allelic
frequencies are maintained if ...
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populations are large,
individuals contribute equally to genetic composition of
next generation, and
matings are random
Remember: Narrow definition of evolution = change
in the genetic frequency of a population.
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Why does this matter?
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If population is not at equilibrium –
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There are outside forces acting on the population.
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Outside forces that can change population
genetics.
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Mutations
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origin of variations, and mutation increases under stress
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Migration
Population size
Non-Random Mating
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Age, chemicals, UV-radiation
Nonrandom Mating: ∆ gene frequencies
Environmental Variance: favor some phenotypes
Effects of Selection: stable polymorphisms
Natural Selection
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Loss of Genetic Variation
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Inbreeding: rapid loss of genes
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Genetic Drift: random losses of genes
Neighborhoods: local breeding tendency
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Fixes traits quickly
Races of plants and animals
Bottlenecks: low population = reduced pool,
duration of the low population is critical (drift)
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•
Survivors of a near-extinction resulted in close
inbreeding 10,000 years ago.
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Current Evolution
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According to narrow definition:
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Evolution is little more than a process that
changes gene frequencies in a non-random
manner;
environmental influences direct this change
What are a few examples of recent evolution
of species that can be correlated to an
environmental stress?
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Examples
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The evolution of
pesticide resistence in
pest species
The evolution of
antibiotic resistence in
human pathogens
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note the recent
discovery of plague and
tuberculosis exhibiting
broad-spectrum
antibiotic resistence
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Insect species resistant to pesticides
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Strep resistance to penicillin
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Maintenance of variation
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So how is variation maintained in the face of
environmental pressures and natural
selection?
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Ever see a constant environment?
Microenvironmental differences exist over small
spatial scales.
Temporal heterogeneity is a common
characteristic of physical environments.
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
“There is grandeur in this view of life, with its
several powers, having been originally
breathed by the Creator into a few forms or
into one; and that whilst this planet has gone
cycling on according to the fixed laws of
gravity, from so simple a beginning endless
forms most beautiful and most wonderful
have been, and are being evolved.”

Charles Darwin – The Origin of Species (Last
sentence)
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END OF CHAPTER 2
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ADDITIONAL INFORMATION
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Genetics review
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The phenotype is the outward expression of an
individual's genotype
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Genotype: unique genetic constitution
Phenotype: outward expression of that genotype
A genotype = set of genetic instructions; blueprints
Phenotype = the expression of that genotype in the
form of an organism
(is that enough? Are there external factors?)
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Effects of environmental influences are like details in a
blueprint that are left to the discretion of the building
contractor.. What does that mean?
More genetics
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All phenotypic traits have:
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Genetic basis + influence by variations in the
environment
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What kind of environmental variations?
Phenotypic plasticity
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Capacity of an individual to exhibit different
responses to its environment
How the individual responds to environmetnal
variation
Genetic variation (review, right?)
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Alleles
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Heterozygous
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Two different alleles for a particular gene
Homozygous
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Different forms of a particular gene
Both copies of a gene are the same
Dominant… Recessive…
Gene pool
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All the alleles of the genes of every individual in a
population
Sources of genetic variation
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How does genetic variation arise?
Mutation
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Any change in the sequence of the nucleotides that
make up a gene or in regions of the DNA that control
the expression of a gene
Consequence?
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Drastic – maybe lethal – changes in the phenotype
No detectable effect – silent mutations
New phenotypes produced  better suited to the local
environment  phenotypes increase
Multiple effects  pleiotropy (effects of a single gene on
multiple traits)
Genetic basis of continuously varying
phenotypic traits

Many phenotypic traits with ecological
relevance vary continuously over a range
of values (eg: body size)
Adaptations result from natural selection on
heritable variation in traits that effect evolutionary
fitness
 The most important consequence of genetic
variation for the study of ecology is evolution by
natural selection
 Evolution
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Any change in a population’s gene pool (what is a
gene pool?)
Individuals whose traits enable them to have higher
rates of reproduction have more offspring  alleles
increase
Adaptations or evolutionary adaptation
Process = adaptation
Adaptation (process of evolution by
natural selection)
Variation among individuals
1.
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Eg – bird beaks; different individuals have
different-sized beaks
Inheritance of that variation
2.
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Size of bird’s beak has an existence of its own in
a population; individual is borrowing that trait
Differences in survival and reproductive
success (or fitness) related to that variation
3.
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Fitness: production of descendants over an
individual’s lifetime.
+ Evolutionary change
Change in a California citrus pest
Cyanide fumigation no longer
effective
Stabilizing, directional, and disruptive
selection
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Stabilizing selection
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Directional
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Individuals with intermediate (average) phenotypes have higher reproductive success
Population moved towards an optimum point
Maintains a single fittest phenotype
When the environment of a population is relatively unchanging: dominant mode; little
evolutionary change
Fittest individual have a more extreme phenotype;
When new optimum reached – becomes stabilizing selection
Disruptive

Increase genetic and phenotypic variation within a population and in the extreme case
creates a bimodal distribution of phenotypes; relatively uncommon; eg: individuals
specializing on one of a small number of food resources; strong competition among
individuals
+
Example of
Disruptive selection
Population genetics and the prediction of
evolutionary change
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Population genetics
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Study of the dynamics of natural selection and genetic change in
populations
Populations are continually engaged in dynamic evolutionary
relationships with their environment that shape their ecological
interactions
(one) Goal of population genetics  to develop methods for
predicting changes in gene frequencies in response to selection
Why?
Ability to predict them can tell us whether the genetic changes we
observe are consistent with our understanding of evolution
(check out the ‘more on the web’ links)
Population genetics and ecologists
every population harbors some genetic variation that
influences fitness .. Potential for evolution exists in all
populations
1.

Except?
Changes in the environment will almost always be met
by an evolutionary response that shifts the frequencies
of genotypes within the population. (translate?)
2.
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Magnitude of the evolutionary response depends on genetic
variation present in the pop at a given time
Rapid environmental changes brought about by the
appearance of new adaptations in populations of
enemies or by human-caused changes in the
environment (eg?) can exceed the capacity of a
population to respond by evolution
3.
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So?