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Leks
Runaway Sexual Selection (Fisher)
Handicap Hypothesis (Zahavi)
Sensory Exploitation Hypothesis (Ryan)
Alternative mating tactics
Internal versus External Fertilization
Satellite males (frogs, crickets)
Ecological Sexual Dimorphisms
Bower birds
Ratites
Bushland tinamou
Lecture # 18
28 March 2017
Female releases eggs first, then male fertilizes them with his sperm,
Female has the first opportunity to desert, male is left in a “cruel bind”
Amplexus
Rhea Paternal Care
Emu
Ostrich Male Parental Care
Emu Male Parental Care
Dinosaur fossils suggest that
male parental care could be
ancestral in birds
If so, ratites could have
retained the ancestral state
And, if so, then female care
and biparental care would be
derived conditions
A male of the medium-sized predatory dinosaur Troodon (North America late Cretaceous)
brooding a large clutch of eggs. Female archosaurs extract substantial amounts of calcium and
phosphorus from their skeletal tissues during egg formation. Histologic examination of cross
sections of bones (femur, tibia, and a metatarsal bone) from an adult Troodon found in direct
contact with an egg clutch revealed little evidence of bone remodeling or bone resorption,
suggesting that the bones were those of a male. Fossilized remains of Troodon and two other
types of dinosaurs found with large clutches of eggs suggest that males, and not females,
protected and incubated eggs laid by perhaps several females (Credit: Bill Parsons)
13
16
9
20
14
11
15
1
4
7
3
11
6
5
Red-eyed Vireo
Ecological
Sexual Dimorphism
Four Possible Situations Involving an Individual’s
Behavior and Its Influence on a Neighbor
__________________________________________________________________
Neighbor(s) Gain
Neighbor(s) Lose
__________________________________________________________________
Individual Gains
Pseudo-altruistic behavior
Selfish behavior
(kin selection)
(selected for)
__________________________________________________________________
Individual Loses
True altruistic behavior
Mutually disadvanta(counterselected)
geous behavior
(counterselected)
_________________________________________________________________
W. D. Hamilton (1964)
Kin Selection
Inclusive Fitness
Hamilton’s rule: r n b – c > 0
r = coefficient of relatedness
n = number of relatives that benefit
b = benefit received by each recipient
c = cost suffered by donor
rnb > c
“Adaptive Geometry of a Selfish Herd”
W. D. Hamilton (born 1 August 1936, died 7 March 2000, age 63)
“I will leave a sum in my last will for my body
to be carried to Brazil and to these forests. It
will be laid out in a manner secure against the
possums and the vultures just as we make our
chickens secure; and this great Coprophanaeus
beetle will bury me. They will enter, will bury,
will live on my flesh; and in the shape of their
children and mine, I will escape death. No worm for me nor sordid fly,
I will buzz in the dusk like a huge bumble bee. I will be many, buzz
even as a swarm of motorbikes, be borne, body by flying body out into
the Brazilian wilderness beneath the stars, lofted under those beautiful
and unfused elytra which we will all hold over our backs. So finally I
too will shine like a violet ground beetle under a stone.
“Adaptive Geometry of a Selfish Herd”
Eusocial Insects
Hymenoptera (“thin wings”)
Ants, bees, wasps, hornets
Workers are all females
Haplodiploidly
Isoptera (“same wings”)
Termites (castes consist of both sexes)
Endosymbionts
Parental manipulation
Cyclic inbreeding
Inclusive fitness should be understood within a multilevel selection
approach, as a nested hierarchy extending from genes, to individuals,
to kin, and finally to even larger groups.
White-Fronted Bee Eaters, Kenya (Emlen and Wrege, Cornell)
Peter
Wrege
Steve Emlen
Helpers at the Nest in White-Fronted Bee Eaters in Kenya
__________________________________________________________________
Breeders
r*
Number of Cases
% Cases
__________________________________________________________________
Father x Mother
0.5
78
44.8
Father x Stepmother
0.25
17
9.8
Mother x Stepfather
0.25
16
9.2
Son x Nonrelative
0.25
18
10.3
Brother x Nonrelative
0.25
12
6.9
Grandfather x Grandmother
0.25
5
2.9
Half brother x Nonrelative
0.13
3
1.7
Uncle x Nonrelative
0.13
2
1.1
Grandmother x Nonrelative
0.13
1
0.6
Grandson x Nonrelative
0.13
1
0.6
Great grandfather x Nonrelative
0.13
1
0.6
Nonrelative x Nonrelative
0.0
20
11.5
Total
174
100.0
__________________________________________________________________
* r = coefficient of relatedness.
S. T. Emlen and P. Wrege, Cornell
Leks
Runaway Sexual Selection (Fisher)
Handicap Hypothesis (Zahavi)
Sensory Exploitation Hypothesis (Ryan)
Alternative mating tactics
Internal versus External Fertilization
Satellite males (frogs, crickets)
Ecological Sexual Dimorphisms
Bower birds
Ratites, Bushland Tinamou
Reciprocal Altruism
Evolution of Self Deceit
Subconscious mind
Polygraph playback experiments
Fool Yourself, The Better to Fool Others
Game Theoretic Approaches
Costs versus benefits of behaviors
“tit for tat” strategy can lead to cooperation
“the future casts a long shadow
back on the present” -- Axelrod
Evolutionarily stable strategies = ESS -- Maynard Smith
(a tactic that when present in a population, cannot be beaten)
Reciprocal Altruism (Trivers 1971)
Donor ––> Recipient
Small costs, large gains, reciprocated
Sentinels
Robert Trivers
Biological basis for our sense of justice?
Friendship, gratitude, sympathy, loyalty,
betrayal, guilt, dislike, revenge, trust, suspicion,
dishonesty, hypocrisy
Game Theoretic Approaches
Prisoner's dilemma:
Two suspects, A and B, are arrested by the police. The police have insufficient
evidence for a conviction, and, having separated both prisoners, each of them
is offered the same deal: if one testifies for the prosecution against the other
and the other remains silent, the betrayer goes free and the silent accomplice
receives the full 10-year sentence. If both stay silent, the police can sentence
both prisoners to only six months in jail for a minor charge. If each betrays the
other, each will receive a two-year sentence. Each prisoner must make the
choice of whether to betray the other or to remain silent. But neither prisoner
knows for sure what choice the other prisoner will make. So the question this
dilemma poses is: What will happen? How will the prisoners act?
Prisoner's Dilemma
Prisoner B Stays Silent
Prisoner A
Stays Silent
Both serve 6 months
Prisoner A
Prisoner A goes free
Betrays
Prisoner B serves 10 years
Prisoner B Betrays
Prisoner A serves 10 years
Prisoner B goes free
Both serve two years
http://plato.stanford.edu/entries/prisoner-dilemma/
Game Theoretic Approaches
Costs versus benefits of behaviors
“tit for tat” strategy can lead to cooperation
(“the future casts a long shadow back
on the present” -- Axelrod)
Evolutionarily stable strategies = ESS
(a tactic that when
present in a population,
cannot be beaten)
John Maynard Smith
Evolution of Self Deceit
Subconscious mind
Polygraph playback experiments
Evolution of Self Deceit
Subconscious mind
Polygraph playback experiments
Fool Yourself
The Better to Fool Others
Summary of Direct Pairwise Interactions Between Two Populations
__________________________________________________________________________
Species
Type of Interaction
A
B
Nature of Interaction
__________________________________________________________________________
Competition
–
–
Each population inhibits the other
Predation, parasitism,
and Batesian mimicry
+
–
Population A, the predator, parasite,
or mimic, kills or exploits members
of population B, the prey, host, or model
Mutualism,
Müllerian mimicry
+
+
Interaction is favorable to both (can
be obligatory or facultative)
Commensalism
+
0
Population A, the commensal, benefits
whereas B, the host, is not affected
Amensalism
–
0
Population A is inhibited, but B is
unaffected
Neutralism
0
0
Neither party affects the other
__________________________________________________________________
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
bees —> clover
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
bees ——> clover
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
mice ——o bees ——> clover
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
cats —o mice ——o bees ——> clover
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
spinsters —> cats —o mice —o bees —> clover
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
spinsters —> cats —o mice —o bees —> clover —> beef
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
spinsters —> cats —o mice —o bees —> clover —> beef —> sailors
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
spinsters —> cats —o mice —o bees —> clover —> beef —> sailors —> naval
prowess
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
—————————————————>
spinsters —> cats —o mice —o bees —> clover —> beef —> sailors —> naval
prowess
Path length of seven! Longer paths take longer (delay)
Longer paths are also weaker, but there are more of them
Indirect Interactions
Trophic “Cascades”
Top-down,
Bottom-up
Competitive Mutualism
Complex Population Interactions
Rob Colwell
Mutualistic Interactions and Symbiotic Relationships
Mutualism (obligate and facultative) Termite endosymbionts
Commensalisms (Cattle Egrets)
Examples:
Bullhorn Acacia ant colonies (Beltian bodies)
Caterpillars “sing” to ants (protection)
Ants tend aphids for their honeydew, termites cultivate fungi
Bacteria and fungi in roots provide nutrients (carbon reward)
Bioluminescence (bacteria)
Endozoic algae (Hydra), “kidnapped” chloroplasts
Endosymbiosis (Margulis) mitochondria & chloroplasts
Birds on water buffalo backs, picking crocodile teeth
Figs and fig wasps (pollinate, lay eggs, larvae develop)
Brown Hydra
Green Hydra
Nudibranchs
Green sea slug
Hydra
Runaway Sexual Selection (Fisher)
Handicap Hypothesis (Zahavi)
Leks
Sensory Exploitation Hypothesis
Internal versus External Fertilization
Alternative mating tactics
Satellite males
Ecological Sexual Dimorphisms
Ratites (bushland tinamou)
Bower birds
Spiteful behavior
Summary of Direct Pairwise Interactions Between Two Populations
__________________________________________________________________________
Species
Type of Interaction
A
B
Nature of Interaction
__________________________________________________________________________
Competition
–
–
Each population inhibits the other
Predation, parasitism,
and Batesian mimicry
+
–
Population A, the predator, parasite,
or mimic, kills or exploits members
of population B, the prey, host, or model
Mutualism,
Müllerian mimicry
+
+
Interaction is favorable to both (can
be obligatory or facultative)
Commensalism
+
0
Population A, the commensal, benefits
whereas B, the host, is not affected
Amensalism
–
0
Population A is inhibited, but B is
unaffected
Neutralism
0
0
Neither party affects the other
__________________________________________________________________
Intraspecific competition (between individuals within spp.)
Interspecific competition (between members of different spp.)
Exploitation competition (resource depression)
Interference competition (direct antagonistic encounters)
Indirect Interactions
Darwin — Lots of “Humblebees” around villages
—————————————————>
spinsters —> cats —o mice —o bees —> clover —> beef —> sailors —> naval
prowess
Path length of seven! Longer paths take longer (delay)
Longer paths are also weaker, but there are more of them
Dan Janzen
Euglossine bees
Orchid fragrances (epiphytes)
Male bees use orchid chemicals as base for production of
pheromones to attract female bees (travel up to 23 km)
pollinate rare and diverse orchids, allowing sparsely
distributed plants to occur at astonishing low densities
Heliconius tropical butterflies
get amino acids from pollen
Larry Gilbert
Various Aspects of the Association of Cattle Egrets with Cattle
________________________________________________________
Number of
Number Percent
Associated Egrets
Category
of Cattle Cattle
Expected
Observed
___________________________________________________________________
Grazing in sun 735
Grazing in shade 55
Standing in sun 146
Standing in shade257
Lying in sun
503
Lying in shade 143
Walking
39
Total
1878
39.1
2.9
7.8
13.7
26.8
7.6
2.1
100.0
239
439
18
21
48
46
84
17
164
69
47
17
13
3
______________________
612
________________________________________________________
Various Aspects of the Association of Cattle Egrets with Cattle
______________________________________________________________________
Mean
Number
Per Minute
Number of Times
Count Was Higher
Than for Opposite
Egret
Number of
Associated Egrets
______________________________________________________________________
Feedings, N = 84
Associated
2.34
58
69
Nonassociated 1.71
26
31
Steps, N = 62
Associated
Nonassociated
20.1
32.1
7
55
Feeding/step, N = 59
Associated
Nonassociated
0.129
0.051
52
7
11
89
Harold Heatwole
88
12
__________________________________________________________
Interspecific Competition leads to Niche Diversification
Two types of Interspecific Competition:
Exploitation competition is indirect, occurs when a
resource is in short supply by resource depression
Interference competition is direct and occurs via
antagonistic encounters such as interspecific
territoriality or production of toxins
Direct versus Indirect Interactions
Exploitation vs. Interference competition
Apparent Competition
Competitive Mutualism
Facilitation
Food Chain Mutualism
Trophic Cascades (top-down, bottom up)
Complex Population Interactions (Colwell’s Plant-Pollinator System)
Mutualisms
Euglossine bees and orchids
Heliconius butterflies (larval nitrogen reserves)
Cattle Egret Commensalism
Gause’s competition lab experiments
Competitive Exclusion
Georgii F. Gause
Coexistence of
two species of
Paramecium
G. F. Gause
Outcome of Competition Between Two Species of Flour Beetles
_______________________________________________________________________________
Temp.
(°C)
Relative
Humidity
(%)
Climate
Single Species
Numbers
Mixed Species (% wins)
confusum castaneum
_______________________________________________________________________________
34
70
Hot-Moist
confusum = castaneum
0
100
34
30
Hot-Dry
confusum > castaneum
90
10
29
70
Warm-Moist
confusum < castaneum
14
86
29
30
Warm-Dry
confusum > castaneum
87
13
24
70
Cold-Moist
confusum <castaneum
71
29
24
30
Cold-Dry
confusum >castaneum
100
0
_______________________________________________________________________________
Recall the Verhulst-Pearl Logistic Equation
dN/dt = rN [(K – N)/K] = rN {1– (N/K)}
dN/dt = rN – rN (N/K) = rN – {(rN2)/K}
dN/dt = 0 when [(K – N)/K] = 0
[(K – N)/K] = 0 when N = K
dN/dt = rN – (r/K)N2
Inhibitory effect of each individual
On its own population growth is 1/K
Assumes linear response to crowding,
instant response (no lag),
r and K are fixed constants
S - shaped sigmoidal population growth
Verhulst-Pearl Logistic
Lotka-Volterra
Competition Equations
competition coefficient
aij = per capita competitive effect
of one individual of species j on
the rate of increase of species i
Alfred Lotka
Vito Volterra
dN1 /dt = r1 N1 ({K1 – N1 – a12 N2 }/K1)
dN2 /dt = r2 N2 ({K2 – N2 – a21 N1 }/K2)
Isoclines:
(K1 – N1 – a12 N2 )/K1 = 0 when N1 = K1 – a12 N2
(K2 – N2 – a21 N1 )/K2 = 0 when N2 = K2 – a21 N1