Transcript Parental Care and Mating Systems

大學部 生態學與保育生物學學程 (必選)
2010 年 秋冬
親代照顧和交配體系
(Parental Care and Mating Systems)
─動物行為學 (Ethology)
鄭先祐(Ayo)
國立 臺南大學 環境與生態學院
生態科學與技術學系 教授
Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/
Part 3. 個體間的互動
 生殖行為 (Reproductive Behavior)
 親代照顧與交配體系 (Parental Care and Mating
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

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Systems)
溝通：管道與功能 (Communication: Channels and
Functions)
溝通的演化 (The Evolution of Communication)
衝突 (Conflict)
團體生活，利他和合作 (Group Living, Altruism,
and Cooperation)
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14 親代照顧和交配體系
(Parental Care and Mating Systems)
 Parental care
 Conflicts (衝突) among family members
 Some factors that influence the allocation of parental
resources
 Overall patterns of parental care
 Dispensing with(免除) parental care– brood parasitism
 Mating systems
 Classifying mating systems
 Monogamy (一對一)
 Polygyny (多妻制)
 Polyandry (多夫制)
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Reproduction is a complicated affair
 In several species of mammals, including humans,
mothers that produce sons incur greater costs than
those that produce daughters
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Higher parasite loads
A delay in the next reproductive effort
Reduced likelihood of future reproduction
Reduced longevity
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Sons are expensive
 Mothers who produce sons experience reproductive
costs

Making them less able to invest in their next child
 Human offspring born after elder brothers had
similar survival
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But lower lifetime reproductive success than offspring
born after elder sisters due to
Lower lifetime fecundity (number of offspring
produced)
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 In a preindustrial human
population in Finland, producing
sons does not affect the survival of
subsequent offspring but does
affect the lifetime reproductive
success of subsequent offspring.
 (a) the probability of surviving to
15 years of age in relation to the
sex of elder offspring.
 (b) Lifetime reproductive success,
defined as number of children
raised to 15 years of age, in
relation to the sex of the elder
offspring.
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Parental care
 Parental investment: investment by parents in an offspring
 That increases the survival of that offspring
 But decreases the ability of investment in other offspring
 Direct parental behaviors
 Have an immediate impact on offspring and their survival
 Nursing, feeding, grooming, transporting, huddling with
young
 Indirect parental behaviors
 Are performed while away from the young
 Do not involve direct physical contact with offspring
 Still affect offspring survival, but not immediately
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Indirect parental care in mammals
 Includes acquiring and defending critical resources
 Building and maintaining nests or dens
 Defending offspring against predators or infanticidal
conspecifics
 Caring for pregnant or lactating females is included
 Pregnancy and lactation are energetically demanding
 Delivering food to females is very helpful
 Male owl monkeys feed lactating females (餵奶的雌性)
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Increases the quantity and/or quality of milk produced
Which reduces the interval between births of offspring
Parents benefit by producing more, well-fed offspring
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Parental investment maximizes
reproductive success
 An individual’s lifetime reproductive success is
maximized
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Not necessarily each reproductive event
 Parents must make two decisions
 How much of their resources to devote to reproduction
instead of to their own growth and survival
 How to allocate available resources among their
offspring
 These decisions can lead to conflicts of interest
 Between parents and offspring
 And among siblings
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Conflicts over parental investment:
sexual conflict
 Sexual conflict: conflict between the evolutionary
interests of males and females
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Particularly mating and parental investment
 Involves interactions between males and females during
which
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Each individual’s fitness depends on its own strategy
As well as the strategy of its partner
 Conflict in parental investment emerges because the costs
of providing care are paid separately by each parent
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Both parents benefit, regardless which one provides the care
Each parent prefers that the other do most the work
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Conflicts over parental investment:
intra/interbrood conflicts
 Intrabrood conflict: young try to obtain resources
 That the parents prefer to distribute to other members of
the current brood
 Interbrood conflict: young try to obtain resources
that parents prefer to save for future offspring
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Differences in the distribution of resources by parents
can lead to sibling rivalry (競爭)
Each youngster derives a greater fitness benefit from
the parental care it receives than from the care its
siblings receive
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Sibling rivalry(競爭)
 Involves overt, substantial aggression
 Can result in siblicide: the death of one or more
siblings
 In other species, rivalry is subtler
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Lower levels of fighting
Scramble competition: siblings race to outcompete
each other for parental resources, with lower levels of
fighting
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Sibling competition in domestic piglets
 Begins before birth
 The uterus is too small to support maximum growth of
embryos
 Some embryos die
 Others survive but have low birth weight
 Are at a severe disadvantage for the intense postnatal
competition
 Piglets(小豬) compete for teats
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Large piglets locate and retain possession of a teat
Smaller piglets are displaced and starve
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Piglet battles
 Battles involve frantic shoving and wounding
 Newborns have slashing canine(犬牙) and incisor(門牙) teeth
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That function solely in early sibling competition
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Siblicide
 Sibling rivalry leads to one offspring attacking and
killing its brother or sister
 Common in species where resources are limited
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And parents deposit eggs or young in a “nursery” with
limited space
Nursery = a uterus, brood pouch, parent’s back, nest, or
den
 It may be advantageous to save the parents time and
energy
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By eliminating the young least likely to reach adulthood
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Factors influencing allocation of parental
resources: life history
 Expected life span influences a parent’s allocation of
resources

To maximize lifetime reproductive success
 Whether parents have future opportunities to breed
 Is affected by the parent’s age and the life span
 In short-lived species with little hope of producing more
young
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Parents invest more heavily in the present young
 Parents of long-lived species spend more of their
resources on their continued growth and survival
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Because they might have the opportunity to breed again
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Parental care in Leach’s storm-petrel
(白腰叉尾海燕)
 Storm petrels are long-lived seabirds
 Adults visit food patches to feed their
chicks
 Foraging trips last two to three days so the
cost of flight is significant
 When parent petrels were handicapped
 They passed the increased reproductive costs to their offspring
 And maintained their own nutritional condition
 Chicks grew more slowly and spent more nights without food
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Parental care in starlings (椋鳥) and tits (山雀)
 When reproductive costs of short-lived starlings and
tits were increased
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They bore part of the increased costs themselves
They allocated the same amount of resources to their
chicks
 In short-lived species
 Each clutch represents a large part of the parent’s
lifetime reproductive success
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Factors influencing allocation of parental
resources: certainty of paternity
 Parental solicitude(掛念) toward young is correlated with
the likelihood of genetic relatedness
 Females are certain that they are related to their offspring

50% of a mother’s genes are present in each of her progeny
 A male cannot be so confident
 He has no guarantee that his sperm fertilizes her eggs
 He risk investing time and energy in raising another male’s
offspring, resulting in
 Decreased chances of evolution of paternal behavior
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Certainty of paternity influences parental
care in sunfish
 Male bluegill sunfish (藍鰓太陽魚) decrease parental care
when they are less certain of their paternity
 Parental males compete for nest sites, guard females and care
for young
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Sneaker males steal fertilizations and do not provide parental
care
 Parental males had chemical cues from fry(魚苗) to
reassess(評估) their paternity
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 Certainty of paternity influences level of parental care by male
bluegill sunfish. (a) In experiment (treatment group) display less
parental care toward eggs than males not exposed to sneaker
males (control group). (b) males whose clutches had been
manipulated (1/3 eggs been exchanged).
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Factors influencing allocation of parental
resources: gender of offspring
 Parental investment is influenced by gender of the
offspring
 Sex allocation: the manner in which parents distribute
resources between sons and daughters
 Parents can bias their allocation in two ways
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
They can produce more offspring of one sex
They can provide more (or better) resources to offspring of
one sex
 Most animals divide resources equally between sons and
daughters
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Others (i.e. brown songlarks) distribute resources unevenly
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Songlarks distribute resources unequally
 Polygynous warblers: one male mates
with more than one female
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Extreme sexual size dimorphism: males
are twice as heavy
Mothers feed the young
 At birth, nestling males and females do
not differ in body mass
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But males become much heavier
Male nestlings receive more, higher
quality prey
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 Songlark mothers bias their parental investment toward their
sons. (1) although male and female nestlings have similar body
masses at hatching, males become increasingly larger than
females in the nest few weeks. (b) mother not only deliver prey
at higher rates to broods with more males, they feed male
nestlings a high quality diet than they feed female nestlings.
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The benefit of raising large male offspring
 Raising male offspring is costly to the mother
 Large body size is an important determinant of male
reproductive success
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Less important for female reproductive success
 By producing large sons that will successfully attract
and compete for mates
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Mothers ensure that their genes are well-represented in
future generations
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Patterns of parental care
 Differences exist among taxa in the extent and pattern
of parental care
 Within vertebrates: most teleost fishes, frogs, toads,
lizards, and snakes show no parental care at all
 All crocodilians and mammals display some form of
parental care

Also typical of most birds
 A few species lay their eggs in the nests of others
 And relinquish all care to the “host” parents
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Female-only care
 The most common form of care in mammals
 Internal gestation and lactation necessitate a major
parental role for the female
 Early paternal care is always in conjunction with
maternal care
 Restricts the ability of the male to help
 Male mammals seek mating opportunities elsewhere
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Biparental care
 The most common form of care in birds
 Birds develop outside the mother’s body
 Male birds are as capable as their mates at providing
care
 Incubation, feeding, and guarding are divided equally
 Two parents are better than one
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Male care in fishes and amphibians
 Can be male-only care or with female care (biparental
care)
 In fishes and amphibians: usually a form of solitary
male care
 These animals rarely feed their offspring
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Parental duties consist of guarding
Performed as well by one parent as by two
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Biparental care in fishes and amphibians
 Biparental care in fish: for survival
and growth of offspring
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Evolved in ciclids (棘鰭類熱帶淡
水魚) because their broods face
intense predation pressure
• Biparental care in discus: the
brood attach themselves to both
parents and feed off parental skin
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Mode of fertilization affects patterns of
parental care
 Reflect basic biological differences: where the young
develop and how they are fed

Reflect ecological conditions (i.e. intensity of predation)
 Teleost fishes, frogs and toads display four categories
of parental care in vertebrates:
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No care
Male-only care
Female-only care
Biparental care
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 Patterns of parental care exhibited by some groups
of vertebrates.
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Size of arrows
reflects the
relative
numbers of
evolutionary
transitions,
and numbers
next to arrows
indicate the
range of
evolutionary
transitions
estimated.
 Diagram showing the major independent evolutionary transitions
among modes of parental care in ray-finned fishes (輻鰭魚綱) .
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Fertilization and parental care
 The association between mode of fertilization and
mode of parental care relates to the proximity of
adults and offspring
 External fertilization in a territory defended by a
male

Is associated with male parental care
 With internal fertilization
 The female carries the embryos
 And is in the best position to care for the young
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Sex roles
Greater female investment in parental care
 In many animals, females provide more parental
investment than males
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Thought to explain sex differences in mating competition
 The sex with greater parental investment (females)
becomes a limiting resource, and

An object of competition among individuals of the sex
investing less (males)
 Because of greater female investment, females select
mates
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Males compete for access to females
This favors large body size and aggressiveness
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Sex role reversal
 The burden of parental care falls on the male
 When parental investment by males is greater
 Males are choosy
 Females are competitive
 Sex role reversal occurs in insects, birds,
crustaceans, fishes, amphibians

Overall, sex role reversed species are in the minority
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Sex role reversal in northern jacanas
 A polyandrous mating system: a female pairs with
several males
 Females defend a territory overlapping several male
territories
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She plays a dominant role in courtship
Females are much larger than males
 Females back up males in confronting potential
predators

She’s more effective than the male at predator deterrence
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African jacana
Males: build nests, incubate eggs, and care for and defend
chicks.
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Brood parasitism
 Intraspecific brood parasites: lay eggs in conspecific’s
nests
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Cliff swallows, red-fronted coots (大鷭) , wood ducks
She may or may not lay eggs in her own nest
 Interspecific (obligate) brood parasites: lay their eggs
in other species’ nests
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They have no other reproductive option
They never build nests
Honeyguides(響蜜鴷), Old World cuckoos(杜鵑), New
World cuckoos, viduine finches, cowbirds, black-headed
ducks
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 Cliff Swallow
 wood ducks
 red-fronted coots
 black-headed
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 Cuckoo Finch
 Cowbird
 Honeyguides (響蜜鴷)
 黃嘴美洲杜鵑
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Raising young brood parasites
 Host parents experience reduced reproductive success
 Damage is directly inflicted by a parasitic adult or its
offspring
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A female cuckoo may eat or throw out the host’s egg
Or kill the young of the host
Nestling cuckoos (杜鵑) evict (逐出) eggs or young from
the nest of their foster parents
Nestling honeyguides(響蜜鴷) kill young with whom they
share the nest
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Brood parasites monopolize parental care
 They mature more rapidly than a host’s young
 Their huge mouths and persistent begging elicit
preferential feeding
 The host’s young may die from starvation, crowding, or
trampling
 Parasitic young may benefit by keeping a few of the
host’s young around
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
Host parents increase the rate at which they feed larger
broods
Host parents may desert single chick broods
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Host species try to avoid being parasitized
 Host species conceal and defend their nests
 Identify and remove the eggs (or young) of parasites
 Brood parasites try to deceive hosts
 Cuckoos lay eggs in the late afternoon when hosts are less
attentive
 Parasitic eggs or young resemble those of the host species
Common cuckoo egg
Great reed warbler egg
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Waxbills (織布鳥)
Whydah (寡婦鳥)
Parasitic
whydah(寡婦鳥)
Waxbill
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Mating Systems
 The ultimate goal of reproduction for both sexes is to
maximize fitness (the relative number of offspring that
survive and reproduce)

The reproductive success of males and females is
constrained by different factors
 A male’s success is limited by access to females
 While a female’s is limited by access to resources
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Increasing reproductive success
 A male can boost his reproductive success by mating
with several females
 A female increases her reproductive success by
gathering more resources

Including male parental care and access to a high-quality
territory
 Males focus on mating effort
 Females emphasize parental effort
 Each parent tries to maximize its own reproductive
success
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Even if this is costly to the other
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Classifying mating systems
 Mating systems are defined based on the number of
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copulatory partners per individual per breeding season
Monogamy: a male and female have only a single
mating partner per breeding season
Polygyny: males copulate with more than one female
Polyandry: females mate with more than one male
Polygynandry (promiscuity): both males and
females mate with multiple individuals
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Ecological factors influence mating systems
 Predation, resource quality and distribution, and
availability of receptive mates affect the need for
 Parental care
 The ability of males to monopolize females
 The ability of females to choose among potential suitors
 Ecological conditions vary
 Flexibility is associated with a species’ mating patterns
 Black howler monkeys
 polygynous in a deciduous habitat
 polygynandrous in a riparian (riverside) habitat
 Monopolizing females by a single male is less likely in
the lush riparian habitat
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Black howler monkeys
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Sexual fidelity(性忠貞) is hard to find in any system
 Social monogamy exclusive living arrangement with one
male and one female

No assumptions about mating exclusivity or biparental care
 Genetic monogamy: an exclusive mating relationship
between one male and one female

Very few species are genetically monogamous
 Some socially monogamous fishes and mammals engage
in extrapair fertilizations

Cuckoldry is a problem for polygynous males
 Extra-pair matings are the rule rather than the exception
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Male extra-pair matings
 A male’s costs: the time and energy in searching for
receptive females other than his mate


While he’s away, his primary mate may copulate with
another male
Reducing his reproductive success
 A male’s benefits: if he successfully inseminates
mates of other males

He can boost his reproductive success
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Female extra-pair matings
 Material benefits:
 A female gets help raising her offspring
 Extra-pair males defend the nest from predators
 Females exchange copulations for a valuable resource, i.e.
food
 Sufficient sperm may be provided to fertilize all her eggs
 Genetic benefits: to obtain “good genes” for their offspring
 Post-fledgling survivorship of the young is related to the
genetic father
 Females of cooperatively breeding bird species avoid mating
with close relatives
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Extra-pair matings in grey-crowned babblers
 They live in social groups of a dominant breeding pair
and nonbreeding helpers
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
Members of the dominant pair may be related
Extrapair young are found in the nest
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Monogamy
 Monogamy: male and female have only a single mating
partner per breeding season
 Sperm from one male is sufficient to fertilize a female’s
eggs


Monogamy is sufficient from the female perspective
For males, confining copulation to a single female
ensures genetic representation in the next generation
 What ecological circumstances favor monogamy over
polygyny?



Necessary biparental care
Distribution of females
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Mate guarding
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Monogamy and biparental care
 When it is necessary or important for offspring
survival

Monogamy may be favored
 Biparental care is more common among birds
 It’s rare in mammals
 Males of some species have parental responsibilities
 And the fitness of both mates depends on the male’s
parental investment
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Male California mice care for their
young
 Fathers participate in all parental activities to the same
extent as mothers
 Once paired, these mice never stray(走散)
 Pups are born at the coldest time of the year and need
their parents’ body heat to survive
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
Both parents take turns huddling over the pups
Removal of fathers resulted in lower pup survival
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Male parental care in rodents
• The mound-building mouse is a monogamous rodent
– Extended pregnancies of females without mates reflect
the high energetic costs of pregnancy and lactation
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Monogamy and distribution of females
 Distribution of females throughout the habitat
influences mating systems
 If it is hard for a male to monopolize multiple mates

Circumstances will favor monogamy over polygyny
 When receptive females are uniformly distributed
 i.e. because they defend exclusive territories
 Monogamy may evolve
 If females are widely dispersed
 It is beneficial for a male to remain with a given female
 The male is at least assured of access to one mate
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Symbiotic shrimp are monogamous
 They live inside the mantle cavity of the pearl oyster
 Pearl oysters are small and scarce
 Shrimp pairs consisted of a male and a female
 Genetic monogamy may occur in
shrimp


Shrimp live in predator-rich
waters and are vulnerable when
away from their hosts
Shrimp that leave may not be
able to re-enter their original
oyster
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Monogamy and mate guarding
 Monogamy may evolve if a male can guard only one
female
 Kirk’s dik-dik (柯氏犬羚) form permanent monogamous
bonds


Dik-diks seem to be faithful to their mates
Genetic analyses revealed no evidence of extra-pair paternity
 Why has such devotion has evolved in dik-diks?
 Paternal care is absent—the male does not defend resources,
reduce predation risk, or commit infanticide
 Some monogamous males defend territories that could
support more than one female
 Females have ample opportunity to wander away
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柯氏犬羚（學名Madoqua kirkii）
 Kirk’s dik-dik (柯氏犬羚)，分布於索馬里南部，
肯亞中南部，坦尚尼亞中北部，安哥拉西南
部和納米比亞。
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Monogamy in dik-diks
 Males prevent other males from knowing when she is in estrus
 He covers up the scent of his female’s dung by scratching dirt
and then defecating on top of it
 He marks his territorial borders with from glands under his
eyes
 If a male tried to overmark the scent of two females


He might fail to mark his territory sufficiently
And lose ownership of the territory
 The female accepts being guarded
 An extra-pair mating might cause a fight between her male and
the rival that could harm her or her offspring
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Polygyny: costs and benefits for males
 Polygyny: one male mates with more than one female
during a breeding season
 A male benefits by producing more offspring


If paternal care is not required
Males maximize reproductive output through multiple
matings
 Costs to a male:
 An increased chance of cuckoldry since he does not guard
each female
 Costs associated with achieving dominance or defending
resources or territories
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Polygyny: costs for females
 Males do not help rear the young
 If males do provide some parental care, it is divided
among offspring

Or sometimes care is provided only to the first female
 They must also share essential resources (nest sites or
territories)

Activity around these areas may attract predators
 Other females may increase competition for resources
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Benefits for females: the polygyny
threshold hypothesis
 Polygyny threshold hypothesis: females gain advantages when
the benefits achieved by mating with a high-quality male
 And gaining access to his resources
 Compensate for the costs
 A female may reproduce more successfully as a secondary mate
on a high-quality territory
 Than as a monogamous mate on a low-quality territory
 Polygyny threshold: the difference in a territory’s quality that
make secondary status a better reproductive option for females
 Females join a harem when they have greater reproductive
success than monogamous alternatives
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The polygyny threshold
 The reproductive success of females decrease as the
harem’s size increases
 Female red-winged blackbirds


prefer unmated males to already mated males
But this is reversed if the territories of mated males are
superior to those of unmated males
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Benefits for females: the sexy son hypothesis
 Access to good genes for her offspring compensates a
female for the costs of polygyny
 A female may benefit if her sons inherit the genes that
made that male attractive

Her sexy sons provide her with many grandchildren
 A female that chooses an already-mated male benefits
indirectly

If the good genes she acquires for her offspring boost
their survival and reproductive success
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Types of polygyny: female defense polygyny
 Female defense polygyny: a male defends a harem of
females

Females live in groups that a male can easily defend
 Female gregariousness(群居) is related to



Cooperative hunting
Increased predator detection
Reproduction
 Female elephant seals form dense aggregations
 Female gregariousness
 Shortage of suitable birth sites
 They return annually to traditional locations
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Female defense polygyny in elephant
seals
 A single dominant male can
monopolize access to 40 or
more females


This male defends his
harem
Against all other male
intruders in bloody, and
sometimes lethal, fighting
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Types of polygyny: resource defense polygyny
 Males defend resources essential to female
reproduction (e.g., nest sites or food)


Rather than defending females
A male can monopolize a number of mates by
controlling critical resources
 Typical conditions include:
 Quality of the monopolized resource reflects male
quality
 Females prefer males with resources over those without
 Males with resources have higher mating and
reproductive success
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Females choose quality resources
 A female’s choice is based on the quality of resources
controlled by a male
 Scorpionfly males fiercely defend the area around a
dead arthropod



The female must copulate to gain access to this food
Larger males obtain larger arthropods
Small males, unable to obtain arthropods, steal
copulations or present salivary secretions (a nuptial gift)
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Scorpionfly (蠍蛉) Panorpa communis
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Types of polygyny: lek polygyny
 Males defend “symbolic” territories
 Located at traditional display sites called leks
 Males do not provide parental care
 They defend only their small territory on the lek
 Not groups of females or resources
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 Two black grouse (黑琴雞) males displaying on a
lek.
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Females visit a lek to select a mate
 Occurs when environmental factors make it difficult for
males to monopolize females directly (female defense
polygyny)

Or indirectly (resource defense polygyny)
 Male sandflies gather on the back of a vertebrate host
and defend small territories




Females visit these nocturnal leks and evaluate several
males
But copulate with just one
Some males copulate with many females
Others will be unsuccessful at finding a mate
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Sandfly
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Evolution of lek behavior: the male’s
perspective
 Males may require specific display habitats
 That are limited and patchily distributed
 Leks may provide protection from predators
 Through increased vigilance
 Leks are information centers
 Males exchange news on good foraging sites
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Hot spot vs. hot shot
 Males gather near “hot spots” where females are most
likely to be encountered
 Less successful males have better mating chances near
highly successful males (“hotshots”)

Less successful males near hotshots obtain more
copulations
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Evolution of lek behavior: the female’s
perspective
 Large groups of males may make mate choice easier
 To distinguish between superior and inferior males
 It may reduce the vulnerability of females to predation
 A predator might be distracted by so many displaying
individuals
 Lek mating may reduce competition between the sexes
for resources
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Polyandry
 Polyandry: a female has more than one mate during the
breeding season
 Female reproductive success can increase with more
mates

If copulation includes critical resources or male parental
assistance
 Polyandrous insects increase the number of eggs laid
(clutch effect) and their hatching success

Reduced risk of fertilization by genetically incompatible
sperm
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Clutch effects and hatching success
 Clutch effects are due to:
 Increased nutrients passed to females
 Increased receipt by females of hormonal stimulants in
male ejaculates
 Hatching success effects include:
 Avoidance of sperm depletion
 Increased genetic diversity among progeny
 Reduced risk of fertilization by genetically incompatible
sperm
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Honey bees are polyandrous
 The queen mates with multiple males
 Increases genetic diversity
 Drones: reproductive males
 Workers: infertile females
 Closely related to the queen
 Diverse colonies:
 More efficient at building combs
 Weigh more
 Survive winter
 Forage at higher rates
 Produce more workers and drones
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Summary
 Evolutionary decisions must be made about
The amount of care and who assumes parental duties
Evolutionary conflicts over parental investment include
 Sexual conflict, intrabrood conflict, interbrood conflict
Avian brood parasites give up parental responsibilities
Conflicts of interest characterize social behavior
 Males produce more offspring by seeking additional mates
 Females emphasize parental effort and produce more
offspring by gaining male parental investment
Mating systems are affected by ecological factors (predation,
resource quality and distribution) and availability of mates





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Summary
 Monogamy: a male and female have a single partner per




breeding season
Polygyny: males copulate with more than one female
Polyandry: females mate with multiple males during the
breeding season
Polygynandry: both males and females mate multiple
times
Extra-pair matings are common


Benefits to males: increased number of offspring
Females gain help in raising offspring, obtaining food,
genetic benefits, fertility insurance, high-quality genes
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問題與討論
[email protected]
 Ayo 台南 NUTN 站
http://myweb.nutn.edu.tw/~hycheng/
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