announcements test results for exam 2 are in! behavior movie tonight at 7pm in evert 151

Announcements

Test Results for Exam 2 are in!

Behavior movie tonight at 7pm in Evert 151

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15 20 25 30 35 40 45 50 55

Mean = 41

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.