Transcript 24_ParentalCare

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Exam 2 Results
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25
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15
10
5
0
15
20
25
30
35
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45
Mean = 41
50
55
Parental care
Very costly behavior
- time
- energy
- vulnerable to predation
emperor penguin
red shouldered hawk
earwig
tarantula hawk
Types of investment
protection from predation
protection from elements
provisioning - feeding, host
emperor penguin
red shouldered hawk
earwig
tarantula hawk
Bigger gametes (increase zygote size and survival)
More gametes (increase potential number of offspring)
Females initial investment more than males
(larger gamete size, internal development in some animals)
Do females have a greater incentive to make sure their initial
investment is not wasted?
If so, females should provide the majority of parental care.
Investment on current offspring
Increased investment = increased probability of young surviving
= increased fitness for parents
Trade off between current and future reproduction?
Time, energy, risks spent by parent on current offspring
(parental investment) can influence possibility of having future
offspring.
Potential tradeoff:
More energy invested now, less energy available for future
reproductive efforts.
Increased parental investment can affect survival of adults.
(potentially decreasing fitness)
Therefore, each increment of parental care is subject to
selection.
cichlid - St. Peter’s fish
Life history traits – characteristics of an individual
that influence survival and reproduction
Age at maturity
House Mouse
African elephant
2 months
11 - 20 years
Atlantic Salmon
3-6 years
Life history traits – characteristics of an individual
that influence survival and reproduction
Number of offspring produced
House Mouse
5-8 young every
month
African elephant
1 calf every
3-8 years
Atlantic Salmon
1,500 to 8,000
eggs once
Life history traits – characteristics of an individual
that influence survival and reproduction
Number of reproductive events
House Mouse
African elephant
~6-12
~3 - 10
(interoparous > 1)
Atlantic Salmon
1
(semelparous = 1)
Life history traits – characteristics of an individual
that influence survival and reproduction
Lifespan
House Mouse
~2 years
African elephant
60 - 70 years
Atlantic Salmon
3-6 years
Remember EPCs…
Parental care should be proportional to probability offspring are
yours.
Females can be quite confident of maternity, males (when females
mate multiply) are less confident of paternity.
- cost / benefit ratio for parenting different between sexes
Variance in reproductive success usually greater for males than
females (for example in polygynous, lekking species).
Times spent caring for offspring = less time getting more mates.
The potential reproductive rate is greater for males than females,
-cost / benefit ratio for parenting different between sexes
Cost of parental care is greater for males.
Operational Sex ratio
(ratio of sexually receptive males to receptive females at any time)
Females limited by number of eggs, gestation, so ratio often male
biased.
cichlid - St. Peter’s fish
However, bi-parental care is common (particularly in birds).
In many species, males provide more care than females.
Australian mallee fowl
African cichlids
greater rhea
seahorses
A female (left) and male
(right) Solenosteira
macrospira .
The male's shell is covered
with numerous egg cases
After mating, females deposit egg cases
on their mate's shell, and the males carry
this burden (which can exceed 50% of the
male's wet mass) until the eggs hatch
Giant water bugs (Belostomatidae)
Large bugs, eggs also larger than typical aquatic insect.
Need to exchange gases (CO2 out, O2 in) which is easier out of
water.
males moisten eggs laid out of water
males carry eggs glued to back
no parental care
Giant water bugs
Are these really the exceptions to the rule?
If males help rear young, fitness increases through
increased young survival.
Parental care is driven by the distribution of resources,
operational sex ratio, previous investment, ecological
conditions…
Caring for the right offspring.
Offspring recognition in colonial species
Mexican free tailed bat
Caring for the right offspring.
Offspring recognition in colonial species
Cliff swallows
can recognize
own young,
rough winged
swallows cannot
colonial cliff swallows
solitary rough winged cliff swallows
Caring for the right offspring.
Offspring recognition in colonial species
colonial cliff swallows
solitary rough winged cliff swallows
Caring for the wrong offspring
It is not worth making a mistake and not caring for your own
offspring! (recognition systems are not perfect)
Communal care of offspring common in some species that live in
groups.
dwarf mongoose
Optimal Threshold Model
signals you want to
accept
signals you want
to reject
acceptance errors
rejection errors
adapted from Reeve 1989, Starks 2003
Caring for the wrong offspring - the extreme
Brood parasites - cowbirds, cuckoos
Caring for the wrong offspring - the extreme
Brood parasites - cowbirds, cuckoos
screaming cowbird
bronzed cowbird
shiny cowbird
brown-headed cowbird
3 species of cowbirds in northern Argentina
bay-winged cowbird
screaming cowbird
colonial, builds
own nests. Egg
dumping?
lays eggs in nests of 1
species - the bay
winged cowbird
shiny cowbird
lays eggs in nests
of 176 species
Sibling conflict
Sibling aggression and siblicide
Occurs when resources are variable or in short supply?
Offspring compete for resources (they only share 50% of genes)
Galapagos
masked booby
blue-footed booby
have two eggs, first
hatched chick always kills
second chick
have two eggs, often
raise two young
Parent offspring conflict (Trivers)
Selection may act on parents and offspring differently.
Some actions that increase fitness of offspring may reduce
fitness of parents.
Parental favoritism
Likely occurs when resources are variable and adults have more
young than they can raise (bet hedging)
Females can invest in eggs differently (even choose sex in some
species).
Young can be fed preferentially.
Seychelles warbler
Parental favoritism
Honest signals of quality in offspring?
barn swallows
Asynchrony in hatching (birth order) can promote or reduce
sibling conflict and parental favoritism
great egret
Can parents control sex of offspring?
Seychelles Warbler
Can parents control sex of offspring?
Haplo / diploid organisms (like ants, bees and wasps)
fertilized egg = female ; un-fertilized egg = male
Temperature Dependant Sex Determination (TSD)
many reptiles
Helpers at the nest
In some animals, juveniles stay to help second nesting effort.
More often female juveniles.
Both direct and indirect benefits.
Direct (learning about maternal care)
Indirect (inclusive fitness by helping rear related offspring
voles
magpie jays
Helpers at the nest
Leads to overlapping generations
Key step in the evolution of sociality?
Genetics basis for mating systems / parental care.
prairie voles
Monogamous, male parental
care
meadow voles
polygynous, no male parental
care
In male prairie voles, vasopressin and dopamine in the
forebrain regulate affiliation between mates (bond
formation).
Vasopressin receptor is expressed at higher levels in
monogamous species than polygynous species.
Lim and colleagues, used a viral vector to transfer the
vasopressin receptor gene from the monogamous species into
the polygynous species.
With this change in a single gene, the polygynous species
essentially becoming monogamous.