Testing hypothesis 2

1
Testing hypothesis 2

• Predict If high Tb harms pregnant females, then
  35o treatment should have
• lower survivorship
• lower growth in mass or length
• Predict If high Tb harms embryos, then 35o
  treatment should have
• more abnormalities
• smaller size at birth (mass, SVL)
• smaller sizes at 9 days

2
Results Effects on females

• None
• Survival 100 for all
• Growth not significantly altered by treatment
• High temperature has no effect on females
  performance

3
Results Abnormalities

• Of 15 females in each treatment
• at 35oC 4 females produced 1 or more abnormal
  or dead offspring
• at 32oC 1 female produced 1 or more abnormal or
  dead offspring
• in Treg no females produced abnormal or dead
  offspring
• abnormalities rather rare, hard to say much

4
Results Effects on embryos
5
Conclusions

• High temperature actually increases development
  rate of embryos
• However, high temperatures reduce mass and SVL at
  birth
• Effects of high temperatures remain for up to 9
  days after birth
• This size effect is probably sufficient to affect
  offspring fitness (survival)

6
Overall conclusions

• Pregant females actively regulate at a lower Tb
  because of negative effects of high temperature
  on offspring fitness
• How might this evolve?
• Quantitative trait Tb when pregnant
• Fitness differential (S) females with Tb 32OC

7
Physiological EcologySummary

• Ecology of individuals
• Adaptive value of physiological traits
• Homeostasis (e.g., thermoregulation)
• How vs. Why questions
• Costs and constraints (e.g., S. merriami)
• Benefits related to fitness (e.g., S. jarrovi)

8
Behavioral Ecology

• Another aspect of the ecology of individuals
• The relationship between the living and nonliving
  environment and the actions of animals

9
Topics within behavioral ecology

• Foraging - how environment influences choice of
  what, how, when, where to eat
• Social systems - how environment influences how
  individuals interact with conspecifics living in
  groups
• Sex and mating systems - environmental
  determinants of mating and reproduction

10
Behavioral ecology focuses on adaptation and
evolution

• Main focus is on the adaptive value of observed
  traits in a given environment
• There can be questions of both how and why
  concerning behavior
• In both cases, approach is similar to that seen
  in physiologial ecology (costs, benefits,
  constraints)

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Living in groups

• Many animals live in groups with conspecifics
• Birds form feeding flocks, migrating flocks
• Herds of herbivorous mammals
• Schools of fish
• Insect aggregations (e.g., monarch butterflies)
• What determines group size?
• What are benefits and costs?

12
Major benefits of group living

• Improved foraging success
• Improved defense against enemies
• Improved ability to cope with the physical
  environment

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End 9th Lecture
14
Improved foraging success of groups

• Improved location of food
• Individuals observe one another and improve their
  chances by watching others succeed
• e.g., blue herons - prefer to forage in areas
  where other herons are already foraging
• species feeding on large ephemeral clumps of
  resources (e.g., fish)

15
Improved foraging success of groups

• Improved probability of capture
• mammals - most predators fail more often than
  they succeed
• lions
• success rate double for 2 lions vs. 1 lion

16
Improved foraging success of groups

• Ability to take larger prey
• group hunters - lion, spotted hyena, wolves, wild
  dog, kill prey gt their own mass
• solitary hunters - leopard, coyote, striped
  hyena, kill prey lt their own mass

17
Improved defense against enemies in groups

• Improved detection of predators
• More eyes, noses, ears
• greater probability of detecting predator
• Bird flocks -- large flocks take flight when
  hawks are farther away
• Advantage does not increase with group size
  indefinitely

18
Improved defense against enemies in groups

• Improved ability to deter a predator
• Groups attack predator (e.g., gulls)
• Chemical deterrence (e.g., pine sawflies)
• Warning coloration - bigger signal

19
Improved defense against enemies in groups

• Confusing a predator
• Many targets in a group -- hard to hit one
• Shoals of fish attacked by squid
• success rate of squid
• single fish gt small shoal gt large shoal

20
Improved defense against enemies in groups

• Dilution effect
• One predator takes one victim
• ? group size, ? individuals prob.(death)
• Have conspecifics nearby so they can be the
  victim
• Effect reduced if
• gt1 individual taken
• prob.(attack) increases with group size

21
Forming selfish herds

• Group cooperation?
• Animals may move to position conspecifics between
  themselves and predators
• If predators take nearest animal, moving to
  center benefits individual
• Result form tight groups because each
  individual selfishly seeks middle

22
Forming a selfish herd
23
Forming a selfish herd
24
Forming a selfish herd
25
Forming a selfish herd
26
Forming a selfish herd
27
Forming a selfish herd
28
Forming a selfish herd
29
Forming a selfish herd

• Point Forming groups does NOT imply cooperation
• Each individual may be acting selfishly for its
  own benefit
• Effects on the group as a whole secondary

30
Improved ability to cope with the physical
environment in groups

• Improved ability to thermoregulate
• e.g., musk ox, roosting bats
• groups minimize cost of thermoregulation by
  clustering
• clustering reduces heat loss

31
Benefits of group living weighed against costs

• Aggressive interactions between conspecifics
• Sharing resources that may be scarce
• Nonexclusive access to mates
• Disease transmission

32
End 10th Lecture
33
Mating systems

• Who mates with whom
• Environment influences the mating system

34
Sexual Selection

• Selection that arises when individuals of one sex
  (usually ??) gain advantages over other members
  of that sex in acquiring mates.
• Darwin originated the concept
• Now viewed as a subclass of natural selection

35
Two kinds of sexual selection

• Intrasexual selection typically ?-? competition
• ?? compete for access to ??
• Darwin power to conquer males in battle
• Weapons large, strong, aggressive ??

36
Characters for combat
37
Two kinds of sexual selection

• Intersexual selection typically ? choice of
  mates
• ?? prefer ?? with particular characters
• Darwin power to charm females
• showy structures, behaviors

38
Characters to charm ??
39
Mating systems

• Description of who mates with whom?
• Differential investment of ?? and ??
• ?? - high cost gametes
• produce few gametes
• choosy
• low variation in reproductive success
• ?? - many, low cost gametes
• produce many gametes
• indiscriminant
• high variation in reproductive success

40
Mating systems

• Promiscuous
• all individuals mate with a number of mates
• marine invertebrates, many insects, some fish,
  nearly all plants
• Polygynous
• ?? mate with gt1? ?? mate with 1? at a time
• many mammals, some birds, many insects, many
  amphibians

41
Mating systems

• Polyandrous
• ??mate with gt1? ?? mate with 1? at a time
• a few birds, a few insects, a few fish
• Monogamy
• 1? with 1?
• many birds, some mammals, a few insects, some
  fish

42
Mating systems depend on ecological conditions

• Territories for mating, breeding (e.g., birds)
• Resources (e.g., food, nest sites)
• Defense against enemies
• ? gets material benefits from choosing certain ??

43
Mating systems depend on ecological conditions

• Resources uniformly spread
• ?? gain most by seeking unmated ?
• no sharing resources
• Monogamy
• Resources patchy (best males--best patches)
• ?? may gain most by seeking best ? (best patch)
  even if he has a mate
• Polygyny

44
End 11th Lecture
45
Polygyny threshold
46
Ecology and mate choice

• Distribution of resources influences mate choice
• all territories good, resources uniform -
  monogamy
• territories vary a lot in resources - polygyny

47
Ecology and mate choice

• What about cases where there is no material
  benefit?
• Why should females prefer showy males?
• Male quality
• colors, ornaments, songs, displays etc. are
  costly
• good males can pay that cost
• handicap principle
• Presumes quality is heritable

48
Parasite-mediated sexual selection (Hamilton-Zuk
Hypothesis)

• Why should females prefer showy males?
• Enemies (specifically parasites)
• parasitized males have reduced showiness
• showy colors ? males resistant to local parasites
• resistance to parasites heritable
• benefit of choosing those males ? resistant
  offspring
• ectoparasites of birds - gnaw feathers
• endoparasites - general reduction in vigor