Announcements
Test Results for Exam 2 are in!
Behavior movie tonight at 7pm in Evert 151
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Exam 2 Results
tarantula hawkred shouldered hawk
emperor penguin
Parental care
Very costly behavior - time- energy- vulnerable to predation
earwig
Types of investment
protection from predationprotection from elementsprovisioning - feeding, host
tarantula hawk
emperor penguin
red shouldered hawk earwig
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.
Bigger gametes (increase zygote size and survival)
More gametes (increase potential number of offspring)
Time, energy, risks spent by parent on current offspring (parental investment) can influence possibility of having future offspring.
Investment on current offspring
Increased investment = increased probability of young surviving = increased fitness for parents
Trade off between current and future reproduction?
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
11 - 20 years 3-6 years
Atlantic SalmonAfrican elephant
2 months
House Mouse
Life history traits – characteristics of an individual that influence survival and reproduction
Atlantic SalmonAfrican elephantHouse Mouse
1 calf every 3-8 years
1,500 to 8,000 eggs once
5-8 young every month
Number of offspring produced
Life history traits – characteristics of an individual that influence survival and reproduction
Atlantic SalmonAfrican elephantHouse Mouse
Number of reproductive events
~3 - 10 1~6-12
(semelparous = 1)(interoparous > 1)
Life history traits – characteristics of an individual that influence survival and reproduction
Atlantic SalmonAfrican elephantHouse Mouse
Lifespan
60 - 70 years 3-6 years~2 years
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
Remember EPCs…
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.
African cichlidsAustralian mallee fowl
seahorsesgreater rhea
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.
Giant water bugs
no parental care
males moisten eggs laid out of water
males carry eggs glued to back
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
colonial cliff swallows solitary rough winged cliff swallows
Cliff swallows can recognize own young, rough winged swallows cannot
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
adapted from Reeve 1989, Starks 2003
signals you want to accept
signals you wantto reject
acceptance errors rejection errors
Caring for the wrong offspring - the extreme
Brood parasites - cowbirds, cuckoos
Caring for the wrong offspring - the extreme
Brood parasites - cowbirds, cuckoos
screaming cowbird brown-headed cowbirdbronzed cowbird shiny cowbird
screaming cowbirdbay-winged cowbird shiny cowbird
lays eggs in nests of 176 species
lays eggs in nests of 1 species - the bay winged cowbird
colonial, builds own nests. Egg dumping?
3 species of cowbirds in northern Argentina
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
have two eggs, first hatched chick always kills second chick
blue-footed booby
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
magpie jaysvoles
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.