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 (3): ). Differed by habitat preference Streamside population Very cautious to leave web when capturing prey. Desert-grassland population Not 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 period Humans 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 bird Migrates 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 Patterns Rovers – move straight lines, go further Sitters – 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. RR r r Rr sitter 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. Rr R r RRRr rr 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 gene Function of the hippocampus (center of spatial memory)

Parental Behavior in Mice fos B gene Neurodevelopment 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 snakes Inland 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 value Physiology

Hmmmm, Slugs Isolated newly hatched young showed a preference based on population 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 Organizational Structure produced during development due to hormonal condition Ex. Neurological structures in male birds Activational Behavior 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 Doves Breeding behavior/cycle Assume – 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 courtship Presence 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 production Crop milk in dove, milk in mammals Generally stimulates proper parental behavior Inhibits sexual behavior Inhibits FSH and LH production Maintains incubation behavior

Feeding Offspring Requires parental care for survival Prolactin 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 definition Everything 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 birds Happens each spring and goes away each fall. Saves 15-20% energy use over the year. Neurogenesis in rat sexual behavior Testosterone “activation” causes slight change in neural anatomy Creates machinery to do behavior.

More Examples Neurogenesis in hippocampus Involved 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 labor Some individuals stay in the colony longer than normal Others start foraging up to 2 weeks sooner.

Environmental Factors Food availability in the hive If you remove food from the hive, more active to forage. If more larvae (or larval scents) the workers forage more. Social encounters with foragers If 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 familiarity Ex. 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 olfaction Major 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 study Mates 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.