Presentation on theme: "Father of Ethology: Konrad Lorenz, A medical doctor in the German army Four years in a Russian POW camp Father of Ethology: established Max Plank Institute."— Presentation transcript:
Father of Ethology: Konrad Lorenz, A medical doctor in the German army Four years in a Russian POW camp Father of Ethology: established Max Plank Institute Dept of Comparative Ethology Nobel laureate Author of “On Aggression” in which he argued that even humans have innate aggressive tendancies Born and raised in Ohio Professor at OSU Performed critical first experiments in behavior genetics demonstrating that two genes control hygienic behavior in honeybees Father of Behavior Genetics: Walter Rothenbuhler
The birth of modern behavior genetics: American foulbrood disease in honeybees Caused by a spore-forming bacteria Highly resistant to treatment Spores last for years in hive products Can result in the death of the hive In the 1940’s it was discovered that some hives could effectively manage AFB by uncapping infected larval cells and dragging the infected larvae out of the colony before it became infectious 1960’s Rothenbhuler demonstrates that two separate and recessive genes control uncapping and removal behaviors This behavior effectively controls this and a variety of other foulbrood diseases.
Tracheal mites get into the trachea of honeybees lay eggs which clog the trachea, eventually suffocating the bee. Bob Danka demonstrated that some bees could effectively resist the mite These bees used their middle leg to groom the mites away from the tracheae preventing infestation. He also found that this grooming behavior was controlled by a single dominant gene. Tracheal mite control behaviors in honeybees: A single a dominant gene allele
Roving vs sitting fruit fly larvae: Environmental variation can favor expression of recessive traits Rovers and sitters can be classified by distance they travel in a petridish over the course of 5 min.
Crossing pure rover females with pure sitter males results in F 1 generation that is all rovers F 2 generation that is 75% rovers 25% sitters Thus, roving behavior is produced by a classic single dominant gene trait. Roving vs sitting fruit fly larvae: A single gene case Experiment: What might happen under high vs low population densities?
Control of behavior by only one or a few genes is relatively rare Examples: Hygienic behavior in honey bees: One “uncapping” gene One “brood-removal” gene Grooming behavior in honey bees Rover vs. sitter fruit flies (1 gene) However, most behavioral traits are polygenic: They are influenced by a large number of genes. Furthermore: Pleiotropy,1 gene influencing several different behavioral phenotypes is also common in the control of behavior. This makes it more difficult to have systematic experimental control.
Suppressed mite reproduction (SMR): Additive genetic traits SMR is an ability to reduce the reproductive success of varroa mites. Chemical Behavioral SMR is an additive trait is controlled by neither dominant or recessive genes. SMR is determined by more than one gene. more of these genes are present, the more of the trait will be expressed.
Example: garter snake preference for the banana slug Natural selection and selective cross breeding
(1) Genes code proteins, not behavior (2) Genes act through the environment Heredity versus environment?? Nature vs nurture?? -- meaningless questions-- What is the moral of the “trading places” story??
Coeffecient of relatedness and predictions of complex genetic influences The coefficient of relatedness (r) between two individuals is defined as the percentage of genes that those two individuals share by common descent. MZ twins = 1.0 DZ twins = 0.5 Siblings = 0.5 Parents & offspring = 0.5 Grandparents & grand children =0.25 If a behavioral trait is under complete genetic control would we predict that r =total variability in the trait?
A measure of how strongly a phenotype is influenced by genetics Total phenotypic variation=VT=VG+VE+VI where: VT= total phenotypic variation observed in a (behavioral) trait VG= variation in population due to genotype VE =variation in population due to environment VI = variation in population due to interaction of VG with VE (i.e. VGxVE) Heritability:
Heritability (H 2 ) H 2 =VG/(VG+VE+VI) = VG/VT again: VT= total phenotypic variation observed in a (behavioral) trait VG= variation in population due to genotype VE =variation in population due to environment VI = variation in population due to interaction of VG with VE and H 2 = heritable variance Characteristics of H 2 Heritability is standardized variance ranging from 0.0-1.0 Indicates what fraction of the total variance in a trait is due to variation in genes: H 2 =0: None of the variance in the trait is influenced by genes H 2 =1: All of the variance in the trait is determined by genes
Two major approaches used by behavior geneticists to study relative contributions of genes & environment in the development of behavior Hold genetic make-up constant to study effects of the environment alone (VT=VE) cross-fostering experiments & twin studies Hold environment constant & explore effects of genes alone (VT=VG) selective breeding experiments use of genetic “knock-outs” Keep in mind: genetic effects are usually complex, involving Pleiotropic and Polygenic effects Environmental effects are complex involving multiple environmental factors Complex genetic and environmental effects will be further complicated by gene/environment interactions.
1 of 6 warbler species that regularly winter in the British Isles, 4 of which are migratory Chiffchaff, Blackcap, Firecrest and Goldcrest winter Atlas 1981-1984, estimates 3,000 Blackcaps