Lecture 14:
Selection
Experiments &
Experimental
Evolution
Irschick, D. J., and D. Reznick. 2009. Field experiments, introductions, and experimental
evolution: a review and practical guide. Pages 173-193 in Experimental Evolution:
Concepts, Methods, and Applications of Selection Experiments. T. Garland, Jr. and M. R.
Rose, eds. University of California Press, Berkeley, California.
1
4 Ways to Study Physiological Evolution
1. Phylogenetic Comparisons of Species (or populations)
Shows what has happened in past evolution
2. Biology of Natural Populations:
extent of individual variation (repeatability)
heritability and genetic correlations
natural and sexual selection
field manipulations and introductions
Shows present evolution in action
3. Selection Experiments
Shows, experimentally, what might happen during future
evolution
4. Compare Real Organisms with Theoretical Models
Shows how close selection can get to producing optimal
solutions
2
Selection Experiments:
1. The earliest form of “genetic engineering”
2. An experimental way to study “evolution in
action”
3. A way to produce “useful” organisms
4. The most direct and convincing test of whether
a trait shows any additive genetic variance in
the population (narrow-sense heritability)
5. A modern corollary to the August Krogh
Principle. If a suitable model does not exist,
then create one!
Bennett, A. F. 2003. Experimental evolution and the Krogh Principle: generating biological novelty
for functional and genetic analyses. Physiological and Biochemical Zoology 76:1-11.
3
Selection Experiments:
6. A way to probe the interrelations among traits
(correlated responses indicate genetic
correlations)
7. A way to test hypotheses about trade-offs and
constraints
8. A way to help find the genes that underlie
phenotypic variation. Crossing a selected
population with a non-selected or oppositelyselected population facilitates genetic
mapping.
4
Selection Experiments:
9. A powerful way to demonstrate
mechanism, i.e., how organisms work:
a. Select on an organismal trait
b. Observe correlated response in lowerlevel trait that you hypothesize causes
the organismal difference
c. Test that hypothesis by performing a
second experiment, selecting on the
lower-level trait
d. Does the organismal trait change as
predicted?
5
Hypothetical Example 1
a. Select for long life span in mice
b. Observe correlated increase in anti-oxidant
enzyme activities
c. Select for high anti-oxidant enzyme activities
(e.g., biopsy individuals to score their
phenotype and then choose breeders)
d. Does life span increase as predicted?
6
Hypothetical Example 2
a. Select for high maximal O2 consumption
b. Observe increase in blood [hemoglobin]
c. Select for high blood [hemoglobin]
d. Does VO2max increase as predicted?
7
Recent Physiological Perspectives
Gibbs, A. G. 1999. Laboratory selection for the comparative physiologist. Journal of Experimental
Biology 202:2709-2718.
Harshman, L. G. , and A. A. Hoffmann. 2000. Laboratory selection experiments using Drosophila:
what do they really tell us? Trends in Ecology and Evolution 15:32-36.
Bennett, A. F. 2003. Experimental evolution and the Krogh Principle: generating biological novelty
for functional and genetic analyses. Physiological and Biochemical Zoology 76:1-11.
Garland, T., Jr. 2003. Selection experiments: an under-utilized tool in biomechanics and
organismal biology. Pages 23-56 in V. L. Bels, J.-P. Gasc, A. Casinos, eds. Vertebrate
biomechanics and evolution. BIOS Scientific Publishers, Oxford, U.K.
Bradley, T. J., and D. G. Folk. 2004. Analyses of physiological evolutionary response.
Physiological and Biochemical Zoology 77:1-9.
Swallow, J. G., and T. Garland, Jr. 2005. Selection experiments as a tool in evolutionary and
comparative physiology: insights into complex traits - An introduction to the symposium.
Integrative and Comparative Biology 45:387-390.
Swallow, J. G., J. P. Hayes, P. Koteja, and T. Garland, Jr. 2009. Selection experiments and
experimental evolution of performance and physiology. Pages 301-351 in Experimental
Evolution: Concepts, Methods, and Applications of Selection Experiments, T. Garland, Jr.,
and M. R. Rose, eds. Univ. of Calif. Press, Berkeley.
Feder, M. E., T. Garland, Jr., J. H. Marden, and A. J. Zera. 2010. Locomotion in response to
shifting climate zones: not so fast. Annu. Rev. Physiol. 72:167-190.
8
Types of "Selection Experiments"
Domestication:
The process may vary widely, e.g., dogs, cats, cattle, horses,
corn.
At some point, it involves some unintentional selection (e.g.,
ability of organisms to reproduce in altered conditions).
Domestication often also involve some intentional selection for
particular characteristics, such as tameness or coloration.
Further selection may occur for particular traits (e.g., milk yield
in cows) or to differentiate breeds based on various traits.
9
Domestication followed by Intentional Selection:
10
Modern European
radiation
Parker et al. 2004 Science 304: 1160-4
11
Mass-adjusted Log(MEI)
Aggressive breeds have higher
daily metabolizable energy intake (MEI)
r = 0.83
2.90
N=9
2.85
No mention of selection on
food consumption…
P = 0.02
2.80
Changed as a correlated
response to selection on
aggressiveness?
2.75
2.70
What physiological or
neurobiological mechanism
might cause that?
2.65
2.60
70
80
90
100
110
120
130
Aggressiveness score
Loadings:
Aggression to dogs and territorial defence
Careau et al. Am Nat 2010
12
Pasi, B. M., and D. R. Carrier. 2003. Functional trade-offs in the limb muscles of dogs selected for running vs. fighting.
Journal of Evolutionary Biology 16:324-332.
Kemp, T. J., K. N. Bachus, J. A. Nairn, and D. R. Carrier. 2005. Functional trade-offs in the limb bones of dogs selected for
running versus fighting. J. Exp. Biol. 208:3475-3482.
13
Domestication:
(http://ngm.nationalgeographic.com/2011/03/taming-wild-animals/ratliff-text/2)
Siberia - Dmitri K. Belyaev developed colonies of silver
foxes, river otters, minks, and rats, starting in 1959.
14
Domestication:
Siberia - Dmitri K. Belyaev developed colonies of silver
foxes, river otters, minks, and rats, starting in 1959.
Frank Albert, a graduate student at the Max Planck
Institute for Evolutionary Anthropology in Germany, is
studying two colonies of tame and hyperaggressive
Siberian rats to determine the genetics behind their
differences. A handful of genes could be responsible.
http://www.nytimes.com/imagepages/2006/07/25/science/25rats2_ready.html
http://ngm.nationalgeographic.com/2011/03/taming-wild-animals/musi-photography
15
Artificial Selection:
Captive populations in which individuals in each generation are
measured for a phenotypic trait (or combination of traits).
Some top or bottom fraction of individuals is then chosen as the
breeders to produce the next generation. This is called
"truncation selection" or "mass selection."
One variation is taking the highest-scoring (or lowest-scoring)
male and female from within each family.
Within-family selection increases the effective population size
(Ne), reduces rate of inbreeding, and helps to eliminate
confounding influences of some maternal effects.
But, it also reduces the possible intensity of selection as
compared with "mass selection," which involves choosing
breeders without regard to their family membership.
16
The longestrunning
vertebrate
artificial
selection
experiment:
Body Mass (g)
Mice
Male mice
at 42 days
of age
67 grams
100
gens.
30 grams
Generation
Bunger, L., A. Laidlaw, G. Bulfield, E. J. Eisen, J. F. Medrano, G. E. Bradford, F. Pirchner, U.
Renne, W. Schlote, and W. G. Hill. 2001. Inbred lines of mice derived from long-term growth
selected lines: unique resources for mapping growth genes. Mammalian Genome 12:678-686.
17
Laboratory Natural Selection:
Individual phenotypes are not measured each generation,
nor are breeders specifically chosen by the investigator.
Rather, a freely breeding population is exposed to altered
environmental conditions, such as different temperatures
or salinities, or to altered husbandry conditions, which
could favor changes in demographic schedules.
Assuming that additive genetic variance exists for relevant
traits, the population will adapt to the new conditions.
Most common with non-vertebrates, including Drosophila,
bacteria, and viruses, but have also been employed with
vertebrates:
Barnett and Dickson housed mouse colonies at
room temperature or around 0o Celsius.
18
Barnett, S. A., and R. G. Dickson. 1984b. Milk production and consumption and growth of young of wild mice
after ten generations in a cold environment. Journal of Physiology 346:409-417.
In only 10 generations,
"Eskimo mice" evolved
to be larger and to
have more body fat for
their body size.
19
Intentional Field Introductions & Manipulations:
David Reznick's guppies in Trinidad
Reznick, D. N., F. H. Shaw, F. H. Rodd, and R. G. Shaw. 1997. Evaluation of the rate of evolution in natural populations of
guppies (Poecilia reticulata). Science 275:1934-1937. Plus comment on page 1880.
Anolis lizards introduced to Caribbean islands
(Tom Schoener, Jonathan Losos)
Losos, J. B., K. I. Warheit, and T. W. Schoener. 1997. Adaptive differentiation following experimental island colonization in
Anolis lizards. Nature 387:70-73.
Losos, J. B., D. A. Creer, D. Glossip, R. Goellner, A. Hampton, G. Roberts, N. Haskell, P. Taylor, and J. Ettling. 2000.
Evolutionary implications of phenotypic plasticity in the hindlimb of the lizard Anolis sagrei. Evolution 54:301-305.
Losos, J. B., T. W. Schoener, and D. A. Spiller. 2004. Predator-induced behaviour shifts and natural selection in fieldexperimental lizard populations. Nature 432:505-508.
20
"Accidental" Introductions & Manipulations:
Drosophila introduced to North America
Huey, R. B., G. W. Gilchrist, M. L. Carlson, D. Berrigan, and L. Serra. 2000. Rapid evolution of a geographic cline in size in an
introduced fly. Science 287:308-309.
Calboli, F. C. F., G. W. Gilchrist, and L. Partridge. 2003. Different cell size and cell number contribution in two newly established
and one ancient body size cline of Drosophila subobscura. Evolution 57:566-573.
House Sparrows
Parkin, D. T., and S. R. Cole. 1985. Genetic differentiation and rates of evolution in some introduced populations of the House
Sparrow, Passer domesticus in Australia and New Zealand. Heredity 54:15-23.
Adaptations of fishes to ponds heated by nuclear power
plants
Smith, M. H., M. W. Smith, S. L. Scott, E. H. Liu, and J. C. Jones. 1983. Rapid evolution in a post-thermal environment. Copeia
1983:193-197.
Adaptations of plants to living on mine tailings
Macnair, M. R. 1987. Heavy metal tolerance in plants: A model evolutionary system. Trends in Ecology and Evolution 2:354359.
Adaptations of rodents to poisons
Smith, P., M. G. Townsend, and R. H. Smith. 1991. A cost of resistance in the brown rat? Reduced growth rate in warfarinresistant lines. Functional Ecology 5:441-447.
21
Examples of
Selection
Experiments
22
Falconer, D. S. 1992. Early selection experiments. Annu. Rev. Genet. 26:1-14.
All the experiments described so far were done by geneticists. Tryon, in
contrast, was a psychologist and he was not primarily concerned with the process
of selection itself. ... The objectives of applying selection were to find out how
the learning ability was inherited, to produce divergent strains, and to identify the
behavioral and physiological traits associated with the maze learning. …
The experiment was started in 1926 and the first publication was in 1929.
Selection was made in both directions for the number of errors made in running
the maze, and was carried on for 21 generations. Unfortunately inbreeding was
practiced, as in most experiments at that time. ... The responses continued for
about seven generations, after which there was hardly any overlap between the
distributions of the two lines. … The experiment provided very convincing
evidence that heredity was one of the factors contributing to the differences
between individual rats in their ability to learn a maze. Crosses between the
selected lines showed that the inheritance was polygenic. Subsequent … studies
… showed that the differences were not in general learning ability, but were rather
specific; for example, the maze-dull rats were more easily distracted by the noises
made by the mechanical maze used for the selection (11).
23
Falconer, D. S. 1992. Early selection experiments. Annu. Rev. Genet. 26:1-14.
All the experiments described so far were done by geneticists. Tryon, in
contrast, was a psychologist and he was not primarily concerned with the process
of selection itself. ... The objectives of applying selection were to find out how
the learning ability was inherited, to produce divergent strains, and to identify the
behavioral and physiological traits associated with the maze learning. …
The experiment was started in 1926 and the first publication was in 1929.
Selection was made in both directions for the number of errors made in running
the maze, and was carried on for 21 generations. Unfortunately inbreeding was
practiced, as in most experiments at that time. ... The responses continued for
about seven generations, after which there was hardly any overlap between the
distributions of the two lines. … The experiment provided very convincing
evidence that heredity was one of the factors contributing to the differences
between individual rats in their ability to learn a maze. Crosses between the
selected lines showed that the inheritance was polygenic. Subsequent … studies
… showed that the differences were not in general learning ability, but were rather
specific; for example, the maze-dull rats were more easily distracted by the noises
made by the mechanical maze used for the selection (11).
24
Falconer, D. S. 1992. Early selection experiments. Annu. Rev. Genet. 26:1-14.
All the experiments described so far were done by geneticists. Tryon, in
contrast, was a psychologist and he was not primarily concerned with the process
of selection itself. ... The objectives of applying selection were to find out how
the learning ability was inherited, to produce divergent strains, and to identify the
behavioral and physiological traits associated with the maze learning. …
The experiment was started in 1926 and the first publication was in 1929.
Selection was made in both directions for the number of errors made in running
the maze, and was carried on for 21 generations. Unfortunately inbreeding was
practiced, as in most experiments at that time. ... The responses continued for
about seven generations, after which there was hardly any overlap between the
distributions of the two lines. … The experiment provided very convincing
evidence that heredity was one of the factors contributing to the differences
between individual rats in their ability to learn a maze. Crosses between the
selected lines showed that the inheritance was polygenic. Subsequent … studies
… showed that the differences were not in general learning ability, but were rather
specific; for example, the maze-dull rats were more easily distracted by the noises
made by the mechanical maze used for the selection (11).
25
Rats
Tryon, R. C. 1929. The genetics of learning ability in rats. Univ. Calif. Publ. Psychol. 4:71-89.
26
Rats
Ridley, 1996, p. 45
Hunt, H. R., C. A. Hoppert, and S. Rosen. 1955. Genetic factors in experimental rat
caries. Pages 66-81 in R. F. Sognnaes, ed. Advances in experimental caries
research. American Association for the Advancement of Science, Washington, D.C.
27
Selection for Ethanol Sleep Time in Laboratory Mice
Human alcoholism involves both liking of alcohol and physical effects of (e.g.,
tolerance to) alcohol. This experiment targeted the latter only.
167 min
41.7 min
Plomin, R., J. C. DeFries, and G. E. McClearn. 1990. Behavioral genetics: A primer. 2nd ed. W. H. Freeman, New York. 455 pp.
28
Selection for Ethanol Sleep Time in Laboratory Mice
Note complete
separation of shortand long-selected lines
33.3 min
200 min
Plomin, R., J. C. DeFries, and G. E. McClearn. 1990. Behavioral genetics: A primer. 2nd ed. W. H. Freeman, New York. 455 pp.
29
The Importance of Replication
A study of genetic differences between
any two lines will likely find many that
have nothing to do with the phenotypic
difference of interest.
30
The Importance of Replication
Line differences in the trait under
selection may be caused by:
1. the selective breeding
2. founder effects
3. subsequent genetic drift
4. unique mutations
5. different adaptive responses
31
The Importance of Replication
Line differences in other traits
(correlated responses) may be
caused by:
1. the selective breeding
pleiotropic genetic effects
genetic linkage
2. founder effects
3. subsequent genetic drift
4. unique mutations
5. different adaptive responses
32
Selection on Open-field Activity in Mice
Video
camera
Method developed by
C. S. Hall in 1930s to
measure levels of fear
and “emotional
reactivity” in rodents
33
DeFries, J. C., J. R. Wilson, and G. E. McClearn. 1970. Open-field behavior in mice: selection response and situational generality.
Behavior Genetics 1:195-211.
34
"The foundation population for the selection experiment
consisted of 40 F3 litters which were descendants from an
original cross of two inbred strains of mice (BALB/cJ and
C57BL/6J)."
DeFries, J. C., J. R. Wilson, and G. E. McClearn. 1970. Open-field behavior in mice: selection response and situational generality.
Behavior Genetics 1:195-211.
35
91 cm square
arena; # of
photobeams
crossed in 3
minutes,
summed
over 2 days
The direct
response to
selection.
Note
consistency
of response
between
replicates.
Mice
600 beam breaks
is at most ~ 91 m
Total movement is
~91 m, at an average
(although movement
is actually periodic)
velocity of 0.51 m/s
Important
features of
experimental
design:
replication
up, down,
and control
lines
36
A correlated
response to
selection.
Note
somewhat
lower
consistency
of correlated
response
between
replicates.
37
Coat color
also
changes!
An example of
pleiotropy,
one of the
main causes
of genetic
correlations.
Again, note
consistency of
replicates.
38
"Two inbred strains of mice (BALB/cJ and C57BL/6J)
which differ widely in open-field behavior were crossed …"
Abstract. In segregating F2, F3, and F4 generations, albino
mice had lower activity and higher defecation scores than
pigmented animals when tested in a brightly lighted open
field. These differences persisted when members of an F5
generation were tested under white light, but largely
disappeared under red light. Thus it was concluded that
there is a major gene effect on the quantitative traits of
open-field activity and defecation which is mediated by the
visual system and that albino mice are more photophobic
than pigmented mice under conditions of bright
illumination.
DeFries, J. C., J. P. Hegmann, and M. W. Weir. 1966. Open-field behavior in mice: evidence for a major gene effect mediated
by the visual system. Science 154:1577-1589.
39
Selection for Thermoregulatory Nesting
Lynch, C. B. 1980. Response to divergent selection for nesting behavior
in Mus musculus. Genetics 96:757-765.
The base population was a genetically heterogeneous stock of lab mice (Mus
musculus) originally derived from an 8-way cross among inbred strains.
May be
considered
the first rodent
selection
experiment in
"evolutionary
physiology."
40
Selection for Thermoregulatory Nesting
Lynch, C. B. 1994. Evolutionary inferences from genetic analyses of cold adaptation in
laboratory and wild populations of the house mouse. Pages 278-301 in C. R. B.
Boake, ed. Quantitative genetic studies of behavioral evolution. Univ. Chicago Press.
41
Selection for Thermoregulatory Nesting
The overall realized heritability pooled across lines and replicates was 0.18 + 0.02 (0.15 +
0.03 for high nesting scores and 0.23 + 0.04 for low nesting scores), or 0.28 + 0.05 when
adjusted for within-family selection.
r = h2 s
h2 = r/s
42
Selection for Thermoregulatory Nesting
Cotton Used in 4 Days (g)
Lynch, C. B. 1994. Evolutionary inferences from genetic analyses of cold adaptation in laboratory and wild populations of the house mouse.
Pages 278-301 in C. R. B. Boake, ed. Quantitative genetic studies of behavioral evolution. Univ. Chicago Press.
60
50
High
40
30
20
Control
10
Low
0
0
5
10
15
20
25
30
Generation
35
40
45
Cause of limit in low lines is obvious:
you cannot go below zero.
43
What Caused the Selection Limit in the High Lines?
44
Why a Selection Limit?
Quantitative-Genetic Answers:
Exhausted Additive Genetic Variance
Genetic Correlations with Other Traits
Counterposing Natural Selection
Traditional,
Interesting,
Black Box
45
Why a Selection Limit?
Abstract: To test the hypothesis that large, well-built, nests are an
important component of fitness, we kept 12 mating pairs of two highselected, two control, and two low-selected lines, selected for
thermoregulatory nest-building behavior, at 22 and 4 degrees C with
access to 10 g of cotton to build a nest, for a period of 180 days.
Measurements included number of lifters born per family, number of
young per litter born and surviving up to 40 days of age, nest type
built by the parents, and weight gain of the young from weaning (20
days of age) to 40 days of age. In all lines the production and
survival of offspring was substantially decreased at 4 degrees C
compared to 22 degrees C, but the high-selected lines produced
more and better-quality offspring, surviving up to 40 days of age at
both temperatures compared to the control and low-selected lines.
This indicates that thermoregulatory nest-building behavior and
evolutionary fitness are closely associated.
So, we do not seem to have Counterposing Natural Selection.
Bult, A., and C. B. Lynch. 1997. Nesting and fitness: lifetime reproductive success in house mice bidirectionally selected for thermoregulatory nest-building
behavior. Behavior Genetics 27:231-240.
46
Why a Selection Limit?
Functional Answers:
Stopped here
19 Feb. 2015
Motivation to build nest at a maximum
Not enough time or space to build larger
Not enough time or space to eat
Energetic cost is too high
Hyperthermia (literally overheating) or possibly
negative feedback to the thermoregulatory
behavior of nest-building
Not mutually exclusive,
May elucidate mechanisms
of evolutionary “constraints”
47
Selection for Treadmill Endurance in Laboratory Rats
"The starting population was 96 male and 96 female genetically
heterogeneous rats (N:NIH stock) obtained from a colony maintained
at the National Institutes of Health. Each rat in the founder
population was of different parentage, so selection was not among
brothers and sisters, which broadens the genetic variance."
Koch, L. G., and S. L. Britton. 2001. Artificial selection for intrinsic aerobic endurance running capacity in rats.
Physiological Genomics 5:45-52.
48
Selection for Treadmill Endurance in Laboratory Rats
Koch, L. G., and S. L. Britton. 2001. Artificial selection for intrinsic aerobic endurance running capacity in rats.
Physiological Genomics 5:45-52.
49
Selection for Treadmill Endurance in Laboratory Rats
Females
Distance Run (m)
Males
50
Selection for Treadmill Endurance in Laboratory Rats
Fig. 6. Change in body weight for
females (A) and males (B) at each
generation of selection for the low
(solid bars) and high (open bars)
lines. For both sexes, the low line
became heavier and the high line
became lighter as a function of
selection for running capacity across
the six generations. At generation 6
(G6), the body weights of the low
and high females differed by 34 g
(20%, P , 0.001) and the body
weights of the low and high males
differed by 40 g (16%, P , 0.001).
*P , 0.05, significant weight change
different from generation 1 (G1)
values within each line as assessed by
the Dunnett test. Values are
means 6 1 SE.
51
Remember that narrow-sense heritability indicates
whether a trait tends to "run in families" and can
be estimated as the slope of the regression of
offspring mean on midparent mean …
52
Mean of Offspring - Trait A
Least-squares linear regression to estimate heritability
3
2
N = 50
1
0
-1
Y = 0.80 X - 0.03
2
R = 0.56
-2
-3
-3
-2
-1
0
1
2
3
Mean of Parents - Trait A
53
Similarly, a genetic correlation indicates whether
two traits tend to "run in families" and can be
estimated as the slope of the regression of
offspring mean for one trait on midparent mean
for the other trait (or vice versa) …
54
Mean of Offspring - Trait B
This plot indicates
that that Traits A and
B tend to go together
in families, and so are
positively genetically
correlated.
3
2
1
Therefore, selection to
increase one would
also cause an
increase in the other.
0
-1
-2
-3
-3
-2
-1
0
1
2
3
Hypothetical example:
Trait A might be body
mass and Trait B
might be tail length.
Mean of Parents - Trait A
55
A correlated response to selection indicates the
presence of a genetic correlation.
In rats, treadmill endurance capacity and body
mass are negatively genetically correlated.
In mice, voluntary wheel running and body mass
are negatively genetically correlated.
(next lecture on Garland mice)
56
Continued Selection for Treadmill Endurance in Lab Rats
Wisløff, U., S. M. Najjar, Ø. Ellingsen, P. M. Haram, S. Swoap, Q. Al-Share, M. Fernstrom, K. Rezaei, S. J. Lee, L. G. Koch, S. L.
Britton. 2005. Cardiovascular risk factors emerge after artificial selection for low aerobic capacity. Science 307:418-420.
57
Selection for Treadmill Endurance: Various Correlated Responses
Lack of control line means
we don’t know if HCR are
better than average rats or
LCR are worse than
average, or both.
Wisløff, U., S. M. Najjar, Ø. Ellingsen, P. M. Haram, S. Swoap, Q. Al-Share, M. Fernstrom, K. Rezaei, S. J. Lee, L. G. Koch, S. L.
Britton. 2005. Cardiovascular risk factors emerge after artificial selection for low aerobic capacity. Science 307:418-420.
58
Selection for Treadmill Endurance in Laboratory Rats
The amount of
voluntary exercise
has also diverged.
HCR
LCR
Exercise behavior
is genetically
correlated with
exercise ability
(performance
capacity). Why?
Waters, R. P., K. J. Renner, R. B. Pringle, C. H. Summers, S. L. Britton, L. G. Koch, and J. G. Swallow. 2008. Selection for
aerobic capacity affects corticosterone, monoamines and wheel-running activity. Physiology & Behavior 93:1044-1054.
59
Selection for Training Response (Plasticity) in Rats
Adaptational response to aerobic exercise was artificially selected for across one generation in a
founder population of 20 female and 20 male genetically heterogeneous rats (N:NIH). Selection
for low and high response was based on the change in treadmill running capacity, assessed by
meters (m) run to exhaustion before and after 24 days of modest treadmill running.
Troxell, M. L., S. L. Britton, and L. G. Koch. 2003. Selected contribution: Variation and heritability for the adaptational response
to exercise in genetically heterogeneous rats. Journal of Applied Physiology 94:1674-1681.
60
The bank vole, Clethrionomys glareolus
Did not get to this in Winter 2014
Sadowska, E. T., K. Baliga-Klimczyk, K. M. Chrzascik, and P. Koteja. 2008.
Laboratory model of adaptive radiation: a selection experiment in the bank vole.
Physiological and Biochemical Zoology 81:627-640.
61
can be reared in lab
62
Goal of Koteja's Selection Experiment
Mimic an "adaptive radiation" from a generalized
omnivorous rodent and develop:
Herbivores
(e.g., Microtus voles)
Predators
(e.g., Onychomys)
Highly-Aerobic Runners
(e.g., chipmunks)
63
Design of Koteja's Selection Experiment
16 lines have been established:
4 selected for ability to maintain body
mass on a low-quality diet
4 selected for high predatory aggression
on crickets
4 selected for high aerobic capacity
measured during swimming
4 unselected, control lines
~3,500-4,000 animals/generation
64
The ability to cope with a low-quality of food:
changes of body mass during a 4-day trial
standard food
low-quality food (dried grass)
65
65
The ability to grow on a herbivorous diet:
body mass change in a test with low-quality diet
Generations 0-3: Sadowska et al. 2008, Physiol. Biochem. Zool.
66
Predatory behavior:
proportion of "predatory" individuals
Generations 0-3: Sadowska et al. 2008, Physiol. Biochem. Zool.
67
The aerobic capacity:
VO2max during swimming
relaxed
selection
Generations 0-3: Sadowska et al. 2008, Physiol. Biochem. Zool.
68
Cumulative effects of the selection:
differences between lines in SD units
Generations 0-4: Swallow, Hayes, Koteja and Garland 2009, in: Experimental Evolution:...
69
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Koteja_Sel_Exp_Voles_UC
R_26_April_2012_v3.pptx
70
Falconer, D.S. (1992) Early selection experiments. Annu.
Rev. Genet. 26: 1-14.
R. Tryon
All the experiments described so far were done by geneticists. Tryon, in contrast, was
a psychologist and he was not primarily concerned with the process of selection itself. He studied
the ability of rats to learn a maze. The objectives of applying selection were to find out how the
learning ability was inherited, to produce divergent strains, and to identify the behavioral and
physiological traits associated with the maze learning. (Tryon’s papers are hard to obtain but for
accounts of his experiment, with references, see refs. 11, 20, 24, 29).
The experiment was started in 1926 and the first publication was in 1929.
Selection was made in both directions for the number of errors made in running the maze, and was
carried on for 21 generations. Unfortunately inbreeding was practiced, as in most experiments at
that time. The selection in both directions was undeniably successful. The responses continued for
about seven generations, after which there was hardly any overlap between the distributions
of the two lines. The mean number of errors was reduced by 33% in the "maze-bright" rats and
increased by 37% in the "maze-dull" rats. (See refs. 24, 29 for graphs of the responses and ref. 11
for graphs of the distributions.) The experiment provided very convincing evidence that heredity
was one of the factors contributing to the differences between individual rats in their ability to
learn a maze. Crosses between the selected lines showed that the inheritance was polygenic.
Subsequent behavioral studies of the lines showed that the differences were not in general learning
ability, but were rather specific; for example, the maze-dull rats were more easily distracted by the
noises made by the mechanical maze used for the selection (11).
71
Bult, A., and C. B. Lynch. 1996. Multiple selection responses in house mice bidirectionally
selected for thermoregulatory nest-building behavior: crosses of replicate lines. Behavior Genetics
26:439-446.
Bult, A., and C. B. Lynch. 1997. Nesting and fitness: lifetime reproductive success in house mice
bidirectionally selected for thermoregulatory nest-building behavior. Behavior Genetics 27:231240.
Bult, A., and C.B. Lynch. 2000. Breaking through artificial selection limits of an adaptive behavior
in mice and the consequences for correlated responses. Behavior Genetics 30:193-206.
Bult, A., L. Hiestand, E. A. Van der Zee, and C. B. Lynch. 1993. Circadian rhythms differ between
selected mouse lines: a model to study the role of vasopressin neurons in the suprachiasmatic
nuclei. Brain Research Bulletin 32:623-627.
Bult, A., E. A. Van der Zee, J. C. Compaan, and C. B. Lynch. 1992. Differences in the number of
arginine-vasopressin-immunoreactive neurons exist in the suprachiasmatic nuclei of house mice
selected for differences in nest building behavior. Brain Research 578:335-338.
Kolbe, J. J., M. Leal, T. W. Schoener, D. A. Spiller, and J.
B. Losos. 2012. Founder effects persist despite adaptive
differentiation: a field experiment with lizards. Science.
72
Artificial Selection on Longevity in Mice
Nagai, J., C. Y. Yin, and M. P. Sabour. 1995.
Lines of mice selected for reproductive longevity.
Growth, Development & Aging 59:79-91.
Mice were pair-mated, and their offspring from parities
5-9 were used as breeders for the next generation.
Age at Last
Parturition
(days)
Young
Born
Alive
Lifespan
(days)
Selection line 1
297
77
378
Selection line 2
299
83
437
Control line
191
46
347
At gener. 16:
This is covered in 105 Evolution
73
This is covered in 105 Evolution
At generation 89,
selection in the low line
was discontinued
because of poor viability
and an oil concentration
so low that it cannot be
measured. At this point,
the populations had
changed from 4.7% oil
to 19.3% in the high and
1.1% in the low line.
Note physical
lower limit of
zero % oil
Ridley, 1996, p. 238
74
This is covered in 105 Evolution
r = h2 s only works for initial generations
Ridley, 1996, pp. 236-239
75
2004. Genetics 168:2141-2155.
76
Remember that narrow-sense heritability can be estimated
as the slope of the regression of offspring on midparent
mean …
Correlation (bivariate) - relationship between two traits or
variables:
Can be positive or negative
Ranges from -1 to +1
Usually assumed to be linear for purposes
of statistical testing
Pearson product-moment correlation
assumes bivariate normality;
denoted as r or R
Spearman rank correlation is a
"nonparametric" alternative
By itself, correlation does not indicate causation!
77
SCOR1PCT = 100 * (Exam1 + Exam2 + Critique1 + Critique2)/160
Descriptive Statistics
EXAM1
EXAM1PCT
EXAM2
EXAM2PCT
SCOR1PCT
Valid N (lis twis e)
N
Statis tic
41
41
41
41
40
40
Minimum
Statis tic
36.00
60.00
34.00
56.67
68.13
Maximum
Statis tic
58.50
97.50
57.00
95.00
97.19
Mean
Statis tic
Std. Error
49.2073
.9703
82.0122
1.6171
46.9146
.9229
78.1911
1.5382
84.6484
1.0471
Std.
Deviation
Statis tic
6.21287
10.35478
5.90963
9.84939
6.62239
Skewness
Statis tic
Std. Error
-.681
.369
-.681
.369
-.199
.369
-.199
.369
-.458
.374
78