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 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.
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. rover R R Rr Rr r sitter All heterozygous Rr Rr Rr r
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. rover R r RR Rr R rover rr Rr r
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.
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. 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 • 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
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.
Effect of estrodial on embryos Effects of Uterine Hormones
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.
Courtship and Wooing • Visual presence of ♀ produces testosterone production in ♂. • Activates courtship behavior • Male courtship triggers release of follicle stimulating hormone (FSH). • FSH stimulates ovarinegrowth 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