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Limits on adaptation. Different challenges can impose selection on the same trait. Tradeoffs because resources are limited. Constraints that slow or prevent the evolution of an ideal trait. Limits on adaptation. Constraints. – factors that slow or prevent the evolution of an ideal trait.

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Presentation Transcript
slide1

Limits on adaptation

Different challenges can impose selection on the same trait

Tradeoffs because resources are limited

Constraints that slow or prevent the evolution of an ideal trait

slide2

Limits on adaptation

Constraints

– factors that slow or prevent the evolution of an ideal trait

Functional constraints

ex: Darwin’s finches with large

beaks can’t sing complex songs

slide3

Limits on adaptation

Constraints

– factors that slow or prevent the evolution of an ideal trait

Functional constraints

ex: Darwin’s finches with large beaks can’t sing complex songs

Physiological constraints

Why isn’t this flower dropped after pollination?

 find the answer in your textbook!

slide4

Limits on adaptation

Constraints

– factors that slow or prevent the evolution of an ideal trait

Functional constraints

ex: Darwin’s finches with large beaks can’t sing complex songs

Physiological constraints

Why isn’t the flower dropped after pollination?

Developmental constraints

ex: panda’s fifth digit can’t be used to manipulate bamboo

slide5

Limits on adaptation

Constraints

– factors that slow or prevent the evolution of an ideal trait

Functional constraints

ex: Darwin’s finches with large beaks can’t sing complex songs

Physiological constraints

Why isn’t the flower dropped after pollination?

Developmental constraints

ex: panda’s fifth digit can’t be used to manipulate bamboo

Genetic constraints

genetic correlation between two traits can prevent adaptation of both

slide6

Limits on adaptation

Constraints

– factors that slow or prevent the evolution of an ideal trait

Functional constraints

ex: Darwin’s finches with large beaks can’t sing complex songs

Physiological constraints

Why isn’t the flower dropped after pollination?

Developmental constraints

ex: panda’s fifth digit can’t be used to manipulate bamboo

Genetic constraints

genetic correlation between two traits may prevent one trait

Lack of genetic variation (including lack of a preadaptation)

ex: ability to feed on new host plants (text)

slide7

Limits on adaptation

Constraints

– factors that slow or prevent the evolution of an ideal trait

Functional constraints

ex: Darwin’s finches with large beaks can’t sing complex songs

Physiological constraints

Why isn’t the flower dropped after pollination?

Developmental constraints

ex: panda’s fifth digit can’t be used to manipulate bamboo

Genetic constraints

genetic correlation between two traits may prevent one trait

Lack of genetic variation (including lack of a preadaptation)

exaptation (preadaptation) – trait that increases fitness through a particular

function, but has not evolved for that function; an existing trait that is

used for a new function

slide8

Limits on adaptation

Constraints

– factors that slow or prevent the evolution of an ideal trait

Functional constraints

ex: Darwin’s finches with large beaks can’t sing complex songs

Physiological constraints

Why isn’t the flower dropped after pollination?

Developmental constraints

ex: panda’s fifth digit can’t be used to manipulate bamboo

Genetic constraints

genetic correlation between two traits may prevent one trait

Lack of genetic variation (including lack of a preadaptation)

Could the tetrapods have evolved to use the stapes (ear bone) for hearing if they

had not lost their gills?

 read about the evolution of the ear and see what you think!

slide9

Variations on natural selection

Sexual selection– selection via differences in mating success

What happens when selection acts differently on

a trait in males and females?

Life history evolution–

What happens when selection acts differently on a

trait during different portions of the life cycle?

offspring produced at each age

RS

cumulative fitness

future fitness

0 1 2 3 4 5 6 7 8

expression of lethal mutation

age

slide10

Variations on natural selection

Phenotypic plasticity– genotype expressed differently in

different environments

slide11

Variations on natural selection

Phenotypic plasticity can evolve if: heritable

under selection

Genetic variation in phenotypic plasticity

leaf

size

shade

sun

plasticity

Which families are

favored in sun?

in shade?

in env. with both?

1

2

3

4

5

6

7

8

9

family

slide12

Variations on natural selection

Phenotypic plasticity can evolve if: heritable

under selection

Genetic variation in phenotypic plasticity

Is there VP?

variation among

all dots

Is there VG?

variation among

family means

Is there VE?

variation btwn

sun & shade means

leaf

size

1

2

3

4

5

6

7

8

9

family

slide13

Variations on natural selection

Phenotypic plasticity can evolve if: heritable

under selection

Genetic variation in phenotypic plasticity

Is there VP?

Is there VG?

Is there VE?

What accounts for

variation in plasticity?

VG x E

leaf

size

1

2

3

4

5

6

7

8

9

family

slide14

VP

= VG

+ VE

+ VG x E

parent is alcoholic

parent is not alcoholic

env 1

env 1

env 1

env 2

env 2

env 2

Variations on natural selection

Phenotypic plasticity can evolve

genotype x environment

interaction

purely genetic

purely environmental

actual

% alc-

oholic

slide15

VP

= VG

+ VE

+ VG x E

parent is alcoholic

parent is not alcoholic

env 1

env 1

env 1

env 2

env 2

env 2

Variations on natural selection

Phenotypic plasticity can evolve

genotype x environment

interaction

purely genetic

purely environmental

actual

% alc-

oholic