Variation in mortality: grey squirrels
Requirements for natural selection
Mass 200 g
Mate 2x / year
4-8 offspring per litter
Mass of earth: 5.97 x 1027 g
Assume reproduction starts at 6 months (9 in reality)
Assume adults die after 2 litters (20 years in zoos)
How long until squirrels equal mass of earth?
1
28
24
35
20
16
30
12
25
8
4
20
0
9
11
13
15
17
19
21
23
15
28
24
10
20
16
5
12
8
0
4
0
0
9
11
13
15
17
19
21
25
50
75
100
125
150
175
200
225
23
Galen, Zimmer and Newport, 1987.
From Galen 1989
Evidence for Heritability
Gurevitch 1992.
Galen, 1996
2
Floral diameter (mm)
Galen and Newport, 1987
Galen 1989
Effect of natural selection: trait
mean shifts
Bee pollinations
Control pollinations
Corolla length
Corolla length
Galen, 1996
3
Evolutionary Longhand
Modes of selection
Gen. 0
Gen. 1
Gen. 2
Shorthand: Sky pilots with large flowers in the tundra are
adapted to bumblebee pollination
freq.
Longhand:
trait, z
freq.
freq.
trait, z
Mode of selection
freq.
trait, z
Misconceptions
freq.
trait, z
freq.
trait, z
freq.
trait, z
trait, z
4
Sky pilot flowers evolved to become larger in order to colonize the
tundra habitat.
Men who dive for pearls evolve to have a larger lung capacity.
Some species, such as elephants, have only one offspring every five
years. This evolved to protect the species from the problems of
overpopulation.
When the immune system can successfully fight off a disease, new
mutations arise that may allow the disease to elude the immune
system.
[Advanced: why can’t you substitute “groups” for “individuals” in
evolutionary longhand and get evolution of groups?]
Cannings and Cannings. 1999.
5
References
Cannings, R. and Cannings, S. 1999. Geology of British Columbia. Douglas and McIntyre,
Vancouver, BC.
Galen, C. 1989. Measuring pollinator-mediated selection on morphometric floral traits: bumblebees
and the alpine sky pilot, Polemonium viscosum. Evolution 43:882-890.
Galen, C. 1996. Rates of floral evolution: adaptation to bumblebee pollination in an alpine wildflower,
Polemonium viscosum. Evolution 50:120-125.
Galen, C and Newport, M. 1987. Bumble bee behavior and selection on flower size in the sky pilot,
Polemonium viscosum. Oecologia 74:20-23.
Galen, C, Zimmer, K, and Newport, M. 1987. Pollination in floral scent morphs of Polemonium
viscosum: a mechanism for disruptive selection on flower size. Evolution 41: 591-606.
Gurevitch, J. 1992. Sources of variation in leaf shape in two populations of Achillea lanulosa.
Genetics 130:385-294.
Wright, J., Stanton, M, and Scherson, R. 2006. Local adaptation to serpentine and non-serpentine
soils in Collinsia verna. Evolutionary ecology research 8:1-21.
6