Selling an Idea or a Product

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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits ( male
PI) a. food gifts ( nuptial gifts) (can
become ritualized)
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits a.
food gifts 1) nuptial gift of
hanging flies -- male catches insect --
hangs from vegetation releases pheromone to
attract female -- if female accepts food gift,
will allow male to copulate while she eats.

3

• hanging flies
• -- females use of male sperm depends on size of
  food gift
• if large requires about 20 min to consume
  complete transfer of males sperm female does
  not mate again
• if medium-sized requires 10-12 min to consume
  partial sperm transfer female mates with
  additional males
• if small consumed in lt 5 min no sperm transfer

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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits a.
food gifts 2) spermatophore of
katydids crickets -- contains protein
mass eaten by female, used to produce
eggs
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-- female removes and eats protein gift -- as
she eats, sperm migrate from sperm capsule into
her reproductive tract -- after eating the
protein mass, she removes and eats sperm
capsule -- the larger the protein mass, the
longer sperm can migrate into female before she
removes sperm capsule ? decision to use males
sperm is based on spermatophore size
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits a.
food gifts 3) males body

redback spider
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits b.
territory
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits c.
male parental care (good parent
hypothesis) ex 15-spined stickleback --
males build nest and care for eggs -- females
prefer males that shake their bodies more
frequently in courtship -- are better able to
oxygenate eggs
Male nest fanning
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits c.
male parental care ex sedge warbler

-- females prefer males with larger
repertoires -- male repertoire size indicates
ability to feed young
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits c.
male parental care ex blue tit
-- male has bright yellow breast -- females
prefer males with bright yellow color -- color is
carotenoid based obtained from caterpillars and
other insects -- male color may therefore reflect
his foraging success and ability to feed
young Prediction brighter colored males should
have heavier young
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Experiment -- cross fostered nests by switching
complete sets of eggs between different pairs of
parents (to control for genetic effects on
offspring size) -- weight of the fledglings was
a function of the foster fathers yellow
plumage, not the color of the genetic father --
male color is therefore an honest indication
of paternal ability
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 1.
Mate choice based on material benefits c.
male parental care ex weaver
bird
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• Mating Behavior
• II. Sexual Selection
• B. Epigamic Selection Female mate
  choice
• 2. Mate choice without material benefits
• -- female gets only sperm from male
• -- should select male based on some
  assessment of inherent
• quality
• -- should occur even if there are also
  material benefits
• Can females do this?
• If so, what is female assessment based on?
• What do females gain from it? Does it matter
  (does it improve mating success, the quality and
  survival of offspring, etc.)?

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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 2.
Mate choice without material benefits a.
Hypotheses for choice based on male genetic
quality (choice based on traits that accurately
reflect male quality) 1) Healthy
male hypothesis -- females prefer male
traits that accurately reflect a males
immediate health (lack of communicable parasites
diseases) -- male courtship and
adornment reflect disease/parasite load --
decreases risk of contagion for female (and
offspring) -- conveys immediate personal
benefit to female may indirectly
benefit offspring, but is incidental ex
Satin Bowerbird
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-- males give no PI -- have glossy plumage --
build and decorate bower in which female mates
with male (bower ? nest)
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-- males give no PI -- have glossy plumage --
build and decorate bower in which female mates
with male -- males with high quality bowers have
fewer ectoparasites in their feathers
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 2.
Mate choice without material benefits a.
Hypotheses for choice based on male genetic
quality 2) Good genes
hypothesis -- females prefer male traits
that accurately reflect male viability
(heterozygosity disease resistance foraging
ability etc.) -- male courtship and
adornment reflect viability-enhancing
genes -- offspring may inherit viability
advantage -- benefits offspring may have
no immediate benefit to female

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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 2.
Mate choice without material benefits a.
Hypotheses for choice based on male genetic
quality 2) Good genes
hypothesis a) assessment based on male
coloration and courtship display ex.
1 ringneck pheasant
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-- males are polygynous give no PI -- have
bright colored plumage and energetic courtship --
pheasants have two protozoan parasites (Eimeria
Histomonas) can be highly fatal in
chicks
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2 experimental groups of male chicks Exposed
group exposed to parasites as chicks
66 died 34 inherently resistant Unexposed
group not exposed to parasites as chicks
37 died (for various reasons) of
the survivors, some resistant, some
not Allowed to grow up, then gave females a
choice between pairs of exposed and unexposed
males
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• on average, females preferred males from exposed
  group
• -- on average, exposed males had brighter
  colors more energetic courtship displays
• offspring of exposed males had greater resistance
  to parasites than offspring of unexposed males
  resistance ? had heritable components

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Mating Behavior II. Sexual reproduction
B. Epigamic Selection Female mate choice 2.
Mate choice without material benefits a.
Hypotheses for choice based on male genetic
quality 2) Good genes
hypothesis a) assessment based on male
coloration and courtship display
ex. 2 bower birds
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Brain size
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 2.
Mate choice without material benefits a.
Hypotheses for choice based on male genetic
quality 2) Good genes
hypothesis b) assessment based on male
song
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• Ex. 1 Canary (selection for song structure)
• male song has a trill composed of syllables, each
  of two notes
• -- production is physiologically demanding
• -- have upper limit on speed of production and
  frequency bandwidth
• females prefer trills of broad bandwidth sung
  very fast selects for fitter males
• females add testosterone to eggs fertilized by
  these males, which enhances optimal development
  of offspring

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• Ex. 2 Starling (selection for total amount of
  singing)
• Bouts of singing/hr positvely correlated with
  strength of males immune system
• Females prefer males with high song rates
• May convey enhanced immunity to offspring

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• Ex. 3 Sedge warbler (selection for repertoire
  size)
• Female prefer males with larger repertoire
• Repertoire size correlated with male
  heterozygosity (repertoire size also related to
  males ability to feed young)
• Females eggs are somehow fertilized by sperm
  that are genetically least like the eggs genome
• Increases heterozygosity in offspring

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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 2.
Mate choice without material benefits a.
Hypotheses for choice based male genetic
quality 2) Good genes
hypothesis c) assessment based on male FA
(fluctuating asymmetry) variation in
random, minor differences between left
right side structures in bilaterally
symmetrical organisms -- reflects
developmental stabiliity (ability of genome
to resist perturbations and produce a
symmetrical body)
30
Ex Barn swallow -- males have long outer tail
feathers -- females prefer long, symmetrical tail
feathers
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Experiment 1 experimentally shortened or
lengthened tail feathers recorded mating
success
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Experiment 2 experimentally altered degree of
FA in tail feathers
increased FA
control
decreased FA (more symmetrical)

increased FA (less symmetrical

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• Mating Behavior
• II. Sexual Selection
• B. Epigamic Selection Female mate
  choice
• 2. Mate choice without material benefits
• a. Hypotheses for choice based on
  accurate reflection of male
• genetic quality
• 3) Evolutionary consequences of
  choice based on male genetic
• quality
• honest signals complex displays
• Sexual dimorphism male ornamentation
  (adornment)

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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 2.
Mate choice without material benefits b.
Hypotheses for choice based on male
attractiveness (traits that may not accurately
reflect male genetic quality, and may even
reduce survival, but are sexy)
1) Runaway selection hypothesis --
females prefer male traits that are sexually
attractive, even if they do not reflect
something accurate about male quality --
females benefit have sexy sons (and daughters
who prefer sexy males)

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Runaway Selection -- initially females are
selected to prefer male traits that accurately
reflected male quality (ex long, red tail
feathers) -- females who preferred the trait had
more surviving offspring preference was selected
for male trait became sign stimulus -- any
mutation that resulted in exaggerated male trait
( supernormal stimulus) would convey an
advantage to males -- trait therefore becomes
ever more extreme and uncoupled from accurate
indication of male quality -- becomes an
arbitrary preference that may lower male
survival, but persists simply because of female
preference
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Mating Behavior II. Sexual Selection B.
Epigamic Selection Female mate choice 2.
Mate choice without material benefits b.
Choice based on male attractiveness
2) Chase-away selection hypothesis --
males evolve elaborate traits, not driven by
female mating preference, but to exploit
preexisting sensory bias in female --
female receives no benefit for herself or
offspring all benefits go to male

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Chase-away Selection -- mutation yields a trait
in males that taps into preexisting sensory bias
in females (ex females have sensory bias for
red, because red fruit or red insects are high in
carotenoids male mutation causes red
feathers) -- females might prefer red males even
though males may provide no genetic or material
benefits (male trait was never correlated with
genetic quality) -- females will then be selected
to resist the trait, resulting in higher
threshold of stimulation required for trait to
have an effect -- this, in turn, would select for
males to overcome resistance by exaggeration of
trait -- would get an arms race leading to
evolution of elaborate, costly ornaments of no
value to female and useful to male only for
manipulating female choice.
39
Ex Zebra finches -- males and females banded
with different color leg bands -- 100 of
males with red bands had 1 mates 0 with green
bands had mates -- switched red and green bands
between males mating success changed
accordingly -- males with red bands had
multiple mates and gave less PI per female --
female preference therefore potentially lowered
her reproductive success
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Mating Behavior II. Sexual Selection C.
Epigamic Selection Male mate choice 1.
Factors that favor increased male selectivity
-- Increased male PI relative to female
PI male PI ltlt female PI less male
selectivity polygyny male PI ? female PI ?
selectivity male PI gtgt female PI male more
selective than female monogamy,
polyandry
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Mating Behavior II. Sexual Selection C.
Epigamic Selection Male mate choice 2. What
is male choice based on? a. female
size b. virginity

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• Mating Behavior
• II. Sexual Selection
• B. Epigamic Selection Male mate choice
• 3. Evolutionary consequences of male choice
• Decreased sexual dimorphism (esp. for body size)
• Sex role reversal
• requires that male PI gt female PI
• requires that female reproductive capacity gt male
  reproductive capacity (male must be a limiting
  resource that females compete for)
• (Note sex role reversal ? female mimicry)

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Sex role reversal -- requires male PI gt female
PI and reproductive capacity of female gt male Ex
1 Pipe fish Syngnathus typhle -- male has
pouch for holding eggs provides all care for
eggs and young for several weeks -- during this
period, female can produce several clutches of
eggs -- 11 sex ratio, but female biased
operational sex ratio male pouch in short
supply -- females compete for males males are
resistant prefer larger, ornamented
females Complete sex role reversal
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Sex role reversal Ex 2 Sea horse Hippocampus
-- male has placenta-like pouch provides all
care for eggs and young -- female can produce
one clutch of eggs during period of male
care -- 11 sex ratio -- no sex role reversal
monogamy
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• Ex 3 Katydid spermatophore
• Food gift for female
• Parental investment for male up to 25 of body
  weight
• Value to female/cost to male changes with food
  availability
• Low food male can make only one spermatophore
  female can produce several batches of eggs if she
  can get sufficient nutrition
• Leads to sex role reversal females compete for
  extra males

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• Information for 3rd exam stops here
• Exam will cover
• Latter part of Communication (Use of Information
  in Animal Signals)
• Resource Defense and Group Living
• Mating Behavior 1
• Mating Behavior 2 (up through and including sex
  role reversal)

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Mating Behavior III. Mating Systems -- males
and females of the same species typically follow
different mating strategies and thus exhibit
different mating systems within same
population -- ecological factors that determine
the spatial distribution of females, and relative
amounts of female male PI, have major effects
on evolution of male mating systems -- thus,
male mating systems are typically an evolved
response to female mating systems
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Mating Behavior III. Mating Systems A.
Monogamy one sexual partner 1. female
monogamy -- one of the most common of
female mating systems -- serial
monogamy -- social monogamy EPC (
polyandry)
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Mating Behavior III. Mating Systems A.
Monogamy one sexual partner 2. male
monogamy -- rarest of male mating
systems -- selects for increased male
mate choice a. Mate assistance
hypothesis -- female needs male help to
successfully raise young -- if male abandons
female, his reproductive efforts are lost --
many song birds
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Starlings
52
-- some species monogamous for life
Hippocampus, swans -- in many species, monogamous
males are selected to engage in extra-pair
copulations -- monogamous females may also be
selected for EPC
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Mating Behavior III. Mating Systems A.
Monogamy one sexual partner 2. male
monogamy -- rarest of male mating
systems b. Mate guarding hypothesis
(male enforced monogamy) -- females remain
receptive after mating -- females widely
scattered and difficult to locate/defend --
male biased operational sex ratio -- if male
abandons female, unlikely he will find another
and female will mate again ex
prairie voles damselflies
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Mating Behavior III. Mating Systems A.
Monogamy one sexual partner 2. male
monogamy -- rarest of male mating
systems c. Female-enforced monogamy
-- females prevents male from mating with
additional females, to prevent loss of male PI
or competition for resources with young of
2nd female ex Nicrophorous defodiens
(burying beetle)
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-- After carcass is buried, male may climb onto
elevated perch and release pheromone to call a
2nd female -- if paired female detects males
pheromone, she runs over and pushes him off
perch -- if paired female is tethered, male
calls for much longer time
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Mating Behavior III. Mating Systems A.
Monogamy one sexual partner 2. male
monogamy -- rarest of male mating
systems d. Male- and Female-enforced
monogamy -- both partners defend a high
quality mate and/or high quality
territory -- ex cleaner wrasses
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Mating Behavior III. Mating Systems B.
Polygyny 1 male 2 females -- most common
male mating system 1. female defense
polygyny -- when females are clumped and
defendable
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Mating Behavior III. Mating Systems B.
Polygyny 1 male 2 females -- most common
male mating system 2. resource defense
polygyny -- male controls resource used
by multiple females ex cichlid, Lamprologus
callipterus, gather and guard shells attract up
to 14 females
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Mating Behavior III. Mating Systems B.
Polygyny 1 male 2 females 3. scramble
competition polygyny -- females highly
clumped, but undefendable because of
undefendable resources and high intruder pressure
-- highly male biased operational sex
ratio -- females have brief receptive
periods -- no male PI -- often
females gather at breeding area, leads to
explosive breeding
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Mating Behavior III. Mating Systems B.
Polygyny 1 male 2 females 4. lek
polygyny -- females widely and evenly
distributed undefendable -- male
biased operational sex ratio -- females
have prolonged receptive periods -- no
male PI -- selective pressures for
lekking unclear
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males -- typically
considered the rarest mating system for
females -- in 90 of bird species, some
females exhibit social monogamy, but
genetic polyandry extra-pair copulations --
some species show serial monogamy (only 1 male
per breeding attempt, but multiple attempts per
season/life each with a different male) --
some species (honey bee) are always
polyandrous Will focus on factors that favor
polyandry during a given breeding season or
breeding attempt
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 1. genetic
benefits polyandry a. Fertility
insurance hypothesis -- female mates with
several males to reduce chance that some eggs
will remain unfertilized because of unviable
sperm -- female cannot assess male
fertility ex female red-winged blackbird
eggs of polyandrous females more likely
to hatch than monogamous females
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 1. genetic
benefits polyandry a. Fertility
insurance hypothesis ex Gunnisons
prairie dog polyandrous females become
pregnant 100 of time monogamous
females 92 of time (P lt 0.05)
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 1. genetic
benefits polyandry b. Good genes
hypothesis -- female mates with males other
than social partner because they are
genetically superior -- may create sperm
competition -- potentially improves genetic
quality of offspring or results in sexy
sons -- may help explain extra-pair
copulations
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 1. genetic
benefits polyandry b. Good genes
hypothesis ex. Guppies -- if female mates
with gt 1 male, male that has more vigorous
courtship display fertilizes more of her
eggs -- polyandry creates sperm competition
that may contribute to healthier offspring and
sexy sons
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 1. genetic
benefits polyandry c. Genetic
compatibility hypothesis -- mating with
multiple males increases genetic diversity of
sperm available for fertilization --
increases chance that some sperm will have DNA
that is especially good match with DNA of
eggs -- could increase heterozygosity in young
and reduce risk of deleterious homozygous
recessive alleles
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 1. genetic
benefits polyandry c. Genetic
compatibility hypothesis ex Bluethroat
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ex Bluethroat -- tested immune responses of
young sired by social partner (WPY) and
extra-pair partner (EPY) -- paternal half-sibs
of EPYs from their social partner had only
average immune responses --- EPYs were not
universally genetically superior, only for
females who chose them for extra-pair copulations
Neighboring male
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 1. genetic
benefits polyandry c. Genetic
compatibility hypothesis ex honey bee queen
and diploid drones -- honey bee queens are
among most polyandrous of all female
animals mates with 12-17 drones -- honey
bees are haplodiploid -- fertilized egg
(diploid) ? female -- unfertilized egg
(haploid) ? male
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-- csd (complementary sex determining) locus --
highly polymorphic 18 alleles -- heterozygous
female (diploid) -- hemizygous male
(haploid) -- homozygous male (diploid
drone) -- diploid drones are cannibalized by
workers in early development -- high numbers of
diploid drones ? reduces colony growth and
survival -- multiple matings by queens reduces
risk of large proportions of young being diploid
drones
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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 1. genetic
benefits polyandry d. Genetic
diversity (Genetic variability) hypothesis --
polyandry creates a genetically diverse batch of
offspring -- promotes survival of group ex
honey bee queen
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• honey bee queen
• -- polyandry increases diversity in response
  thresholds
• -- allows for fine-tuned, graded responses to
  colony needs
• For maintaining nest homeostasis
• Experiment -- created single-inseminated and
  mulitple-inseminated queens
• -- kept colonies under constant
  elevated or lowered external temperatures
• -- examined ability of workers to
  maintain constant brood
• temperature (34.5 35 oC)

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• honey bee queen
• For disease resistance
• -- polyandry increases disease resistance
• -- makes it less likely that entire colony will
  be lost to massive infection
• Experiment -- created single-inseminated and
  mulitple-inseminated queens
• -- exposed colonies to fungal disease
• -- examined variability in level of
  infection

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Tarpy (2003). Proc. R. Soc. Lond. B.
79

• For colony survival and foraging success
• -- polyandry increases colony survival and
  foraging success
• -- promotes greater communication activity for
  food collection
• Genetically diverse Genetically
  uniform
• Worker pop. 26,700 5300
• Stored food 1390 cm2 990 cm2
• Foragers/min 15 8
• Waggle dancers/unit time 248 182
• Vibration signals/unit time 442 232
• colonies
• Surviving 25 0

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Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 2. material
benefits polyandry -- female mates with
multiple males to get additional material
resources ex Katydids -- in
some species, when food is scarce females are
polyandrous to get extra food for egg
production -- males can produce only
one spermatophore -- ? male PI gt female PI male
repro. capacity lt female repro. capacity -- can
lead to sex role reversal
81
Mating Behavior III. Mating Systems C.
Polyandry 1 female 2 males 2. material
benefits polyandry ex red-winged
blackbirds -- male will allow non-social partner
female to forage on his territory, but only if
she allows EPC -- monogamous females are chased
away
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Mating Behavior III. Mating Systems D.
Polygynandry 2 females 2 males
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Mating Behavior III. Mating Systems E.
Conditional mating systems ex Dunnock
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Dunnock -- male biased operational sex ratio --
female and male PI about equal -- females have
home range area in which they gather food --
males defend territories -- within one
population, can find all possible mating systems
Male territory
Female home range
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Monogamy -- most common breeding system
(52) -- female home range male territory
Polyandry -- 35 of population --
female home range overlaps territory of 2-3
males, all of whom mate with
female -- female mates up to 12 times/hr.
before laying complete clutch of eggs
actively solicits copulation from male she
has spent less time with -- males help
raise young, provided they copulate often
enough
Male territory
Female home range
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Polygynandry -- 9 of population --
home ranges of 2 females overlap territories of
2 males -- each female has her own nest,
but mates with all males and males help
to raise both broods, provided they mate
often enough Polygyny -- rarest mating
system (4) -- male can defend a
territory that incorporates home ranges of 2
females
Male territory
Female home range
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Dunnock ? mating system is conditional and
depends upon area needed by female to obtain
food and extent to which her home range overlaps
with male territory ultimately, mating system
of both males and females depends upon
abundance and distribution of food. If food
is experimentally increased for long enough
periods, population becomes entirely monogamous
or combination of monogamy polygyny