Transcript Document 7708438

Social Relations
Chapter 7
1
Introduction
•
•
•
Behavioral Ecology: Interactions between
organisms and the environment mediated by
behavior.
Sociobiology: Branch of biology concerned
with study of social relations; intraspecific
behavioral interactions.
Fitness: Number of offspring (genes)
contributed by an individual to future
generations.
 Sexual reproduction.
 Survival of young.
2
Introduction
•
Fundamental Question:
 What is male and female ?
 Females produce fewer, larger, more
energetically costly gametes.
 Males produce more, smaller, less
energetically costly gametes.
3
Gamete Dimorphism is Huge
4
Introduction
•
Female reproduction
success is thought to
be limited by resource
access.
Male reproduction
success is limited by
mate access.
Mean # offspring produced
•
140
120
100
80
Males
Females
60
40
20
0
0
1
2
3
Number of mates
5
Introduction
•
Hermaphrodites
 Exhibit both male and female function.
 Simultaneous
 Sequential
 Charnov et.al. identified (3) conditions favoring
hermaphroditic populations:
 Low mobility limiting male:male competition.
 Low overlap in resource demands by male
and female structures.
 Sharing of costs for male and female function.
6
Hermaphroditic Reef Fish
Simultaneous
Protogyny
=♀→♂
Protogyny
=♀→♂
Protogyny
=♀→♂ = ♂→♀
Protandry
7
Mate Choice
•
Sexual Selection
 Differences in reproductive rates among
individuals as a result of differences in
mating success.
 Intrasexual Selection: Individuals of one
sex compete among themselves for
mates.
 Intersexual Selection: Individuals of one
sex consistently choose mates among
members of opposite sex based on a
particular trait.
8
Intrasexual selection
Intersexual selection
9
Mate Choice and Sexual Selection in Guppies
•
Given a choice, female guppies will mate
with brightly colored males.
 Brightly colored males attract predators.
 Color characteristics that have been
shown to confer mating advantage:
 Brightness
 Number of spots
 Total pigmented area
10
Mate Choice Among Scorpionflies
•
Adult scorpionflies (genus Panorpa) feed on
dead arthropods in the forest understory.
 Dead arthropod supplies are often limited.
 Thornhill found that male Panorpa will
take possession of, and guard, dead
arthropods as nuptial offering to female.
 Larger males are more successful.
 Small males offer spit.
11
Nonrandom Mating Among Wild Radish
•
•
Wild radish flowers have both male
(stamens) and female (pistils) parts, but
cannot self-pollinate (self-incompatible)
Marshall found non-random mating in wild
radish populations.
 Interference Competition - Aggressive or
inhibitory interaction between individuals.
 Some characteristic of the pollen from
certain individuals increases pollination
success seed plants.
12
Sociality
•
•
Evolution of sociality is generally
accompanied by:
 Cooperative feeding (or other assistance)
 Defense of the social group.
 Restricted reproductive opportunities.
Cooperation generally involves exchanges of
resources or other forms of assistance.
13
Cooperative Breeders
•
Species living in groups often cooperate in
rearing offspring.
 What benefit do helpers gain ?
 Inclusive fitness: Improve survival and
reproductive rates of family members.
 Inherited territory: May increase
helper’s probability of future
reproduction and recruiting helpers.
– Kin Selection
14
Packer and Pusey studied cooperation
among African lions in the Serengeti.
15
Acorn Woodpeckers (Melanerpes formicivorus)
•Live in groups of up to 16 individuals.
•Cooperative defense of acorn stores and raising of
young.
16
Sociality
•
Eusociality
 More complex level of sociality.
 Three major characteristics:
 Individuals of more than one
generation living together.
 Cooperative care of young.
 Division of individuals into nonreproductive and reproductive castes.
17
18
19
20