Download adapt1

IV. Variation in Quantitative Traits
V. Selection and Adaptation
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
- selection: differential reproductive success
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
- selection: differential reproductive success
- fitness = reproductive success
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
- selection: differential reproductive success
- fitness = reproductive success
- adaptation = a trait or suite of traits that increases
reproductive success.
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
- selection: differential reproductive success
- fitness = reproductive success
- adaptation = a trait or suite of traits that increases
reproductive success.
- exaptation = an adaptation co-opted for a new
function. (flight feathers are an exaptation of thermoregulatory
feathers, which may be an exaptation of feathers initially adaptive
as sexual ornaments).
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
- all traits are NOT ‘adaptations’ – “spandrels of San
Marco” (Gould and Lewontin) – even if we can envision a function for
them.
- some are due to drift in different populations
- some are correlated or linked to adaptive genes
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
C. How do we identify adaptations?
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
C. How do we identify adaptations?
1. Experiment
Zonosemata flies (Family Tephritidae) wave their
banded wings when threatened. Why?
Zonosemata flies (Family Tephritidae) wave their
banded wings when threatened. Are they
mimicking spiders to deter other predators,
mimicking spiders to deter spider predators, or
does it have nothing to do with predation?
(Waving for courtship?)
Housefly..no waving
Responses of other
preds….
ALL
EATEN!!!
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
C. How do we identify adaptations?
1. Experiment
2. Observational Studies
- Do desert lizards thermoregulate behaviorally?
can do the physiological relationships between temp
and metabolism and activity in the lab…, but do they choose areas
that maintain their temp in this range? Go look in an environment
with variable temps, and see if choice meets the adaptive
expectation.
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
C. How do we identify adaptations?
1. Experiment
2. Observational Studies
3. Comparative Method
Some male bats have disproportionately
large testis.
And some evolutionary biologists are
interested in knowing why.
Is it related to sperm competition and social
group size?
- Females in larger groups would have the
chance to mate with more males, so there
would be greater benefit to producing more
sperm…
Looks good, but!
Data points need to be independent,
and these are NOT phylogenetically
independent… if we make them so,
the data set decays to just two
points... Not too conclusive.
Compare sister taxa;
When diverge occurs, does the one with a
bigger social group have big testes?
Compare sister taxa;
When diverge occurs, does the one with a
bigger social group have big testes?
Then, slide each relationship to the origin,
standardizing the divergence to “0”. Are the
endpoints correlated? This controls for
phylogenetic correlations.
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
C. How do we identify adaptations?
D. Constraints on the POWER of selection
- physical constraints:
why do flying fish return to water?
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
C. How do we identify adaptations?
D. Constraints on the POWER of selection
- physical constraints:
- contradictory selective pressures
- historical constraints (extant genome, physiology,
anatomy, behavior)
IV. Variation in Quantitative Traits
V. Selection and Adaptation
A. Definitions
B. Issues
C. How do we identify adaptations?
D. Constraints on the POWER of selection
- physical constraints:
- contradictory selective pressures
- historical constraints (extant genome, physiology,
anatomy, behavior)
- lack of genetic variation
IV. Variation in Quantitative Traits
V. Selection and Adaptation
VI. Levels of Selection
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
In some organisms, the heterozygote produces a preponderance of one gamete
type - this is called "segregation distortion". This gene is at a selective advantage
over other genes at this locus. Of course, as it increases in frequency and more
organisms are homozygous for it, the differential reproduction drops. However,
this can be balanced by the reduced number of gametes these organisms
produce.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
In some organisms, the heterozygote produces a preponderance of one gamete
type - this is called "segregation distortion". This gene is at a selective advantage
over other genes at this locus. Of course, as it increases in frequency and more
organisms are homozygous for it, the differential reproduction drops. However,
this can be balanced by the reduced number of gametes these organisms
produce.
An example is the t-allele in mice. Heterozygotes only produce gametes with the
't' allele - no 'T' gametes.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
In some organisms, the heterozygote produces a preponderance of one gamete
type - this is called "segregation distortion". This gene is at a selective advantage
over other genes at this locus. Of course, as it increases in frequency and more
organisms are homozygous for it, the differential reproduction drops. However,
this can be balanced by the reduced number of gametes these organisms
produce.
An example is the t-allele in mice. Heterozygotes only produce gametes with the
't' allele - no 'T' gametes. However, the rise in frequency of the 't' allele is
balanced at the organismal level by selection against the homozygote - 'tt' is
lethal. So, the allele can not increase in frequency and is dependent upon other
alleles in the population.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
- Stalk-eyed flies, Cyrtodiopsis dalmanni
(Presgraves, et al.1997).
• X(d) meiotic drive element on the X chromosome
causes female-biased sex ratios in natural
populations of both species.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
- Stalk-eyed flies, Cyrtodiopsis dalmanni
(Presgraves, et al.1997).
• X(d) meiotic drive element on the X chromosome
causes female-biased sex ratios in natural
populations of both species.
• spermatid degeneration in male carriers of X(d).
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
- Stalk-eyed flies, Cyrtodiopsis dalmanni
(Presgraves, et al.1997).
• X(d) meiotic drive element on the X chromosome
causes female-biased sex ratios in natural
populations of both species.
• spermatid degeneration in male carriers of X(d).
• balanced by Y-linked and autosomal factors that
decrease the intensity of meiotic drive.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
- Stalk-eyed flies, Cyrtodiopsis dalmanni
(Presgraves, et al.1997).
• X(d) meiotic drive element on the X chromosome
causes female-biased sex ratios in natural
populations of both species.
• spermatid degeneration in male carriers of X(d).
• balanced by Y-linked and autosomal factors that
decrease the intensity of meiotic drive.
• Even a Y-linked polymorphism for resistance to
drive which reduces the intensity and reverses the
direction of meiotic drive.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
- Stalk-eyed flies, Cyrtodiopsis dalmanni
(Presgraves, et al.1997).
• X(d) meiotic drive element on the X chromosome
causes female-biased sex ratios in natural
populations of both species.
• spermatid degeneration in male carriers of X(d).
• balanced by Y-linked and autosomal factors that
decrease the intensity of meiotic drive.
• Even a Y-linked polymorphism for resistance to
drive which reduces the intensity and reverses the
direction of meiotic drive.
• When paired with X(d), modifying Y chromosomes
(Y(m)) cause the transmission of predominantly Ybearing sperm, and on average, production of 63%
male progeny.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
2. Transposable Elements
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
2. Transposable Elements
these genes replicate themselves independently of cell division... they are gene
parasites that make nothing for the cell. yet they increase in frequency relative to
other genes in the genome.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
2. Transposable Elements
3. 'Selfish' Genes (Richard Dawkins)
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
2. Transposable Elements
3. 'Selfish' Genes (Richard Dawkins)
- genes are the fundamental replicators
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
2. Transposable Elements
3. 'Selfish' Genes (Richard Dawkins)
- genes are the fundamental replicators
- genes which confer an advantage, when averaged across other
genetic backgrounds, will be selected for. (Analogy of 'crews')
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
1. Meiotic Drive:
2. Transposable Elements
3. 'Selfish' Genes (Richard Dawkins)
- genes are the fundamental replicators
- genes which confer an advantage, when averaged across other
genetic backgrounds, will be selected for. Analogy of 'crews')
- co-adaptive assemblages and non-additive effects are not explained
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
- some mitochondria in yeast are non-respiring parasites - they survive
but don't produce much energy for the cell. They reproduce fast in a cell.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
- some mitochondria in yeast are non-respiring parasites - they survive
but don't produce much energy for the cell. They reproduce fast in a cell.
- In small populations of yeast, where selection at the organismal level is
weak, there is no cost to the cell to reproducing slowly and the parasitic
mitochondria dominate within cells.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
- some mitochondria in yeast are non-respiring parasites - they survive
but don't produce much energy for the cell. They reproduce fast in a cell.
- In small populations of yeast, where selection at the organismal level is
weak, there is no cost to the cell to reproducing slowly and the parasitic
mitochondria dominate within cells.
- In large populations, where aerobic respiration is advantageous at a
cellular level, cells with parasites are selected against and the frequency of
parasitic mitochondria is reduced.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
- some mitochondria in yeast are non-respiring parasites - they survive
but don't produce much energy for the cell. They reproduce fast in a cell.
- In small populations of yeast, where selection at the organismal level is
weak, there is no cost to the cell to reproducing slowly and the parasitic
mitochondria dominate within cells.
- In large populations, where aerobic respiration is advantageous at a
cellular level, cells with parasites are selected against and the frequency of
parasitic mitochondria is reduced.
- There is a balance of selection at different levels that must be
understood to explain the different frequency of parasitic mitochondria.
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
C. Cell Selection
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
C. Cell Selection
- Cancerous Tumour - cell division increases, and the effects may be
balanced at a higher level (organism).
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
C. Cell Selection
D. Organism Selection (Darwinian)
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
C. Cell Selection
D. Organism Selection (Darwinian)
E. Kin Selection
E. Kin Selection (W. D. Hamilton - 1964)
- related individuals that help one another increase their OWN fitness, because
their alleles occur within THOSE relatives.
E. Kin Selection (W. D. Hamilton - 1964)
- related individuals that help one another increase their OWN fitness, because
their alleles occur within THOSE relatives.
- Parental Care
E. Kin Selection (W. D. Hamilton - 1964)
- related individuals that help one another increase their OWN fitness, because
their alleles occur within THOSE relatives.
- Parental Care
- Helping Behavior by Siblings
Florida Scrub Jay
E. Kin Selection (W. D. Hamilton - 1964)
- related individuals that help one another increase their OWN fitness, because
their alleles occur within THOSE relatives.
- Parental Care
- Helping Behavior by Siblings
- Sterility and Haplodiploidy
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
C. Cell Selection
D. Organism Selection (Darwinian)
E. Kin Selection
F. Group Selection (Wynne-Edwards)
F. Group Selection (Wynne-Edwards)
- Can groups replace one another simply by reproductive success??
F. Group Selection (Wynne-Edwards)
- Can groups replace one another simply by reproductive success??
- First, it would have to be recognized by it's contradiction with organismal
selection.
F. Group Selection (Wynne-Edwards)
- Can groups replace one another simply by reproductive success??
- First, it would have to be recognized by it's contradiction with organismal
selection.
- (Sacrifice of fitness at the population level with increase at the level of the
group).
F. Group Selection (Wynne-Edwards)
- Can groups replace one another simply by reproductive success??
- First, it would have to be recognized by it's contradiction with organismal
selection.
- (Sacrifice of fitness at the population level with increase at the level of the
group).
- Altruism is an obvious example - sacrifice reproduction for benefit of the group...
but it usually doesn't work because f(altruism) declines within the pop!
VI. Levels of Selection
Selection can occur wherever there is differential reproduction among variable
entities.
A. Gene Selection
B. Organelle Selection
C. Cell Selection
D. Organism Selection (Darwinian)
E. Kin Selection
F. Group Selection (Wynne-Edwards)
G. Species Selection
G. Species Selection
G. Species Selection
- Parthenogenesis arises spontaneously, but extinctions are rapid due to lack of
variation and Muller's rachet.
Muller's ratchet is the continuous accumulation of mutations in a lineage.
In sexual reproduction, since only 1/2 of the genes are passed from each parent,
there is a 50% chance that a deleterious new mutation will be purged from the
genome just by chance. And also, even if it is expressed, there will be other
organisms in the pop that did NOT receive it and have higher fitness. So,
selection can purify this sexual population of the deleterious alleles.
But in an asexual lineage, all offspring get the whole genome - even a new
deleterious allele. So, there is no way to purge it from the genome.
In fact, in Daphnia pulex, asexual lineages accumulate deleterious
amino acid substitutions at 4x the rate of sexual lineages (Paland and Lynch
2006, Science 311:990-992).
G. Species Selection
- Parthenogenesis arises spontaneously, but extinctions are rapid due to lack of
variation and Muller's rachet.
So, extinction rates in parthenogenetic lineages are high... and so most lineages
that radiate and produe lots of descendant species are sexual.
G. Species Selection
- Parthenogenesis arises spontaneously, but extinctions are rapid due to lack of
variation and Muller's rachet.
So, extinction rates in parthenogenetic lineages are high... and so most lineages
that radiate and produe lots of descendant species are sexual.
- Certain lineage are more likely to speciate (beetles - small, tough, and easily
isolated...)
G. Species Selection
- Parthenogenesis arises spontaneously, but extinctions are rapid due to lack of
variation and Muller's rachet.
So, extinction rates in parthenogenetic lineages are high... and so most lineages
that radiate and produe lots of descendant species are sexual.
- Certain lineage are more likely to speciate (beetles - small, tough, and easily
isolated...)
SO, as a consequence of survival and speciation rate (reproduction), sexual
lineages and also more rapidly speciating lineages will leave more species and
replace other lineages that die out over time.