The Development of Behavior:

Points

All Behaviors have some genetic basis.Brain structure, vocal anatomy, etc. determined by DNA

and genetic program in part.

Ex. You can learn languages, but yawns, laughs, and giggles are genetic.

Focused on specific genetic differences that led to different behavioral phenotypes.

Study of genetic basis of behavior is still very young.

All traits are ultimately determined by (gene X environment) interaction.

Funnel web spiders

Susan Riechert conducted a study in Arizona on the predatory behavior of Agelenopsis aperta (J. Evol. Bio. 2000. 13(3):541-550).

Differed by habitat preferenceStreamside population

Very cautious to leave web when capturing prey.

Desert-grassland populationNot cautious. Would run out and grab prey

quickly.

“Common Garden” Experiment

Raise individuals from different populations in the same environment.

If they are the same at maturity, then the differences between populations is primarily environmental.

If they are still different at maturity, then the differences are genetically determined.

“Common Garden” Spider Experiment

Results

Differences in predatory behavior persist.

Therefore

Differences are primarily genetically influenced.

Why are the spiders like this?

Ultimate causation for behavior

Findings:

Desert grassland has few spider predators compared to a streamside community.

Predation has be a selective factor.

Also, food in the desert is less abundant.

If you don’t catch the prey item, you may not see any other food from quite some time.

Period Gene (single genes)

All higher animals/organisms have a periodHumans are affected by mutations to the

period gene as are fruit flies.Also effects Blackcap warblers.

In their case, it affects migratory behavior.

European/Africa birdMigrates 2-3,000 miles and crosses the Sahara

Desert.

Background

Nocturnal migratory restlessness

Jump in migratory direction

Use an internal compass influenced by solar and star cues.

Destination Varies Across Europe

3.15 Differences in the migratory behavior of two closely related birds

Test Migratory Directionality

Common Garden Experiment

Young from different populations try to migrate in a set direction

Test Migratory Directionality

Cross-Breeding Experiment

Cross breed individuals from 2 different populations

Phenotype of offspring will often say something about the genetics.

Cross breed the following:

German BCWA (orient ) and Hungarian BCWA (orient )

What do you get when you cross a priest, a rabbi, and a …?

Offspring will orient in a novel direction ( ), which is an intermediate phenotype.

Intermediate phenotype hints at this being a multi-gene trait and having co-dominance.

Another Cross Breeding Experiment

Cross bred a migratory European BCWA with a non-migratory African BCWA.

Offspring show intermediate degree of nocturnal restlessness.

Drosophila Larval Activity

Two Activity PatternsRovers – move straight lines, go furtherSitters – turn frequently went they

move, don’t move far as a result.

Cross-Breeding Experiment

Pure rover strain(♂) X Pure sitter strain (♀)

All F1 offspring are rovers

Probably just 1 gene/2 alleles involved, with rover allele being dominate.

R R

r

r

Rr Rr

Rr Rr

sitt

er

rover

All heterozygous Rr

Cross F1 Generation

Cross Rr x Rr to get F2 generation.

Get a 3:1 ratio of rovers to sitters.de Belle & Sokolowski (1987)

Gotta love Mendelian genetics.

R r

R

r

RR Rr

Rr rr

rove

r

rover

Questions

What maintains both alleles in a population?

Or

Why doesn’t one allele go to fixation?

Possibilities

1. Natural selection may not be acting on this locus.

2. Selection may fluctuate over time.Each allele may be selected at different brief

times, but not long enough to wipe out any one allele.

3. Frequency-dependant selection (F-DS).Occurs when the fitness of an allele (or organism

with allele, is related to its frequency in a population.

Becomes less fit as it increases in frequency toward fixation, and fitness is highest when it is relatively rare.

So ,F-DS maintains genetic polymorphism.

More single gene effects

Learning ability of mice in a water maze.A spatial memory task

Some mice can’t learn, and never do better than random.

This learning disability is traced to a single geneFunction of the hippocampus (center of

spatial memory)

Parental Behavior in Mice

fos B geneNeurodevelopment of the hypothalamus

Through inbreeding, can produce mice that are homozygous for mutant allele.

Act as normal mice except for parental behavior – ♀ are poor mothers and have trouble raising offspring.

Did you know? Schizophrenia in humans is another single organizational gene.

3.18 Social amnesia is related to the loss of a single gene

Artificial Selection Experiment

Experimenter determines the evolutionary fate of phenotypes.

Fact – if difference in behavior are genetically determined, then the population’s behavior phenotype should respond to selection, artificial or otherwise.

Back to BCWA again

Artificially select for migratory or non-migratory individuals in population.Select based on migratory restlessness.

After several generations, one population becomes two (one pure migratory and the other mostly non-migratory.

Nest Building in Mice

Observation: Mice differ in tendency to incorporate cotton into nest.

Hypothesis: This difference is genetic.

Use an Artificial Selection Experiment

Results: get a cotton loving population and a cotton “so-so” population.

Call Duration in Crickets

Cricket calls are ♂ trying to attract mates.

All populations show variation in call length (hours/night).

Artificial Selection Experiments have shown this variation to be genetic.

Can breed long callers and short callers.

Ultimate Question

What do females prefer?

Long calling is a show of fitness.

however,

Short callers get hit by predators less.

Demonstrating Genetic Effects

The four ways to show genetic effects are:

Common garden experiments

Cross breeding experiments

Artificial selection experiments

Transformation experiments(Taking a gene from one organism and placing

it in another).

Genetic Differences in Alternative Phenotypes

May be genetically different “morphs” even within the same sex.Some fish have can several types of males: parental,

female mimic, and sneaker. (will revisit later)

Ex: Crooked-mouth cichlid in African rift lakes.

Right and left-sided morphs present.Eat scales off of the

opposite side of fish.

Crooked-mouth cichlids

Exist in a 50/50 equilibrium of right and left jawed morphs.

Morph condition is largely heritable.

Maintained by frequency-dependant selection.

Garter Snakes

Behavior: Proximate Ultimate

California garter snakesInland population eats fish and frogs, and

refuses banana slugs.No slugs in the inland environment.

Costal population eats slugs as well as fish and frogs.

Genetics Survival valuePhysiology

Hmmmm, Slugs

Isolated newly hatched young showed a preference based on population.

3.21 Response of newborn, naive garter snakes to slug cubes

Common Garden Slug, I mean Experiment

All young in the same environment.

Exposed young to odor of slug.

Inland snakes tongue flicked a few times and lost interest, while coastal showed great interest and flicked a lot.

Cross Breeding

What do we think cross breeding of these populations will cause?

An intermediate.

Ultimate Level

Inland population don’t have slugs, but are exposed to leeches.Active selection against leech-like /slug consumption.

Why? Cause leeches will eat a snake from the inside out!There are few leeches in the coastal population, therefore

no active selection against sluggy things.

What does the fact that some inland snakes will eat slugs mean to you about the populations?

Application to humans

Jack and Oscar

Identical twins separated at birth (one raised as Catholic in Nazi Germany and the other on a Caribbean Island (Jewish) but still similar in many ways.

Both have similar tastes and mannerisms.

Genetic relationship with IQ

If size can be genetically based, then the volume of the skull can be used to measure intelligence, right?

Wrong!However, genetics can influence similarity of

intelligence.I.Q. closer between identical twins than

fraternal twins.

Main Points

Hormonal influences on behavior

Interaction between learning and behavioral development – biased learning focus

Interactive theory of behavioral development

Interactive Theory of Development

Phenotypic development (including behavior) is strongly genetically determined but may take several alternate pathways depending on the environment.Gene X Environment interactions

Environment is very broadly defined.Both internal (hormonal) and external

Effects of Hormonal Environment

OrganizationalStructure produced during development

due to hormonal condition

Ex. Neurological structures in male birds

ActivationalBehavior triggered by hormone that turns

on an organizational effect.

Ex. Actual singing in male birds as adults

Testosterone is Both Organizational and Activational in Mammals

Fixed Action Pattern

An instinctual behavioral sequence that tends to go to completion once activated.

In mammals, the presence of high testosterone in males drives copulatory behavior.

Let’s look at the organization of fixed action patterns.

Uterine Environment in Mammalian Litters

Location during development of embryos along uterine wall influences behavior.

♂ flanked by ♀’s will be less “male”

♀ flanked by ♂’s will be more masculine than normal.

This is due to leaking testosterone and estrodial.

Rodent Porn

Effects of Uterine Hormones

Effect of estrodial on embryos

Another Example

Organizational and Activational effects in bird song.

Ex. Male WCSP and testosterone treated female WCSPs.

Cascade of Activational Events

Ringed DovesBreeding behavior/cycleAssume – all organization effects are

properly in place. aka. normal adults.

Note – there are no seasons to dove breeding, they just breed all year long if they can.

Dove Breeding Behavior

Courtship and Wooing

Visual presence of ♀ produces testosterone production in ♂.Activates courtship behavior

Male courtship triggers release of follicle stimulating hormone (FSH).FSH stimulates ovarine growth and egg (follicle)

development.

Ovarian follicles secrete estrogen as they develop.Estrogen is important for synchronizing

reproductive development in ♀.

Nest Building Stage

Begins shortly after courtshipPresence of nest and nest-building in

general, triggers progesterone release

Progesterone is important for incubation behavior.♂ must participate in nest building,

otherwise no progesterone and no egg incubation behavior later

Egg Laying

Steps 1 and 2 are important for the production of lutinizing hormone (LH) by the ♀ pituitary gland

This stimulates egg laying in the ♀.

Incubation

Starts from presence of eggs and incubation itself.

Stimulates prolactin productionCrop milk in dove, milk in mammals

Generally stimulates proper parental behaviorInhibits sexual behaviorInhibits FSH and LH productionMaintains incubation behavior

Feeding Offspring

Requires parental care for survivalProlactin activates proper parental

feeding behavior in ♀ and ♂.Parental behavior declines as prolactin

declines late in the season.As prolactin , then FHS and LH (in

females)As prolactin , T (in males)

Back to step one again

Organizational and Activational “Complications”

Classical definitionEverything in the neural net is fixed in

adults

But…there are many cases of neurogenesis in adults

Entire brain structures can appear and disappear in some species, depending on the environment.

Examples of Neurogenesis in Adults

Neurogenesis in “singing centers” in brains of birdsHappens each spring and goes away each

fall.Saves 15-20% energy use over the year.

Neurogenesis in rat sexual behaviorTestosterone “activation” causes slight

change in neural anatomyCreates machinery to do behavior.

More Examples

Neurogenesis in hippocampusInvolved with function of memory

Grows with increased use and demand

Neurogenesis in sex changes among some fish species.Big ♀ will become ♂ in adulthood if it

would be more fit.

To Forage or Not to Forage, that is the Question

Hormones are very important in the development of behavior of workers with a bee hive.

The average sterile worker honeybee has about 1 month to live.

During this time, she generally starts out cleaning cells and feeding larvae, then moves on to feeding nestmates and packing pollen, and finally spends the last week or so actively foraging.

Development of Worker Bee Behavior by Age

What drives this behavior?

Appears to be based on juvenile hormone.

Young nurse workers have low levels of juvenile hormone, while older foragers have much higher levels.

Increases in juvenile hormone stimulates changes in workers brains, creating “mushroom bodies”.

3.2 Gene activity varies in the brains of nurse bees and foragers

What cause the hormone change?

Not fixed by age of worker.

If you create a colony of workers all the same young age,

they still divide the laborSome individuals stay in the colony longer

than normal

Others start foraging up to 2 weeks sooner.

Environmental Factors

Food availability in the hiveIf you remove food from the

hive, more active to forage.

If more larvae (or larval scents) the workers forage more.

Social encounters with foragersIf older foragers are present,

but not allowed to forage, the young are happy to stay nurses.

The presence of older foragers inhibits youthful foraging.

Are Hormones Connected to Age or Task?

Early foragers have high levels of juvenile hormone, even higher than older foragers.

Thus, within colony environment can dictate hormonal behavior in bees.

Experiences Determine…

Sexual preferences

Habitat selection as adults

Nest site selection in birds

Species determination

Are you my mother?

Kin recognition (recognition of relatives)Early learning of kin set many future social

interactions as adults.

Kin share common alleles.

Simple rule – if raised in the same brood, then kin (siblings).

Evolved Recognition Systems

Understanding beyond familiarityEx. Ground squirrels can discriminate related strangers

from unrelated strangers.

Seem to be able to do this by “phenotypic matching”Compare the stranger to self

Kin Recognition in Mammals

Done through olfactionMajor histocompatability complex of glycoprotiens

(MHC’s)Important for recognizing self from non-self in

immune system.

Form the basis for phenotype matching in kin recognition

By licking and grooming, coat self in a blanket of MHC’s or recognition compounds.

Remember the human stinky t-shirt studyMates are more attracted to genetically

compatible scents.

Early Experience and Brain Development

Ex. Food storage in birds and spatial memory.

Early experience with food storing as a young adult ( > 1 month old) causes a larger, more developed hippocampus in Chickadees.