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Announcements. Candidate genes for behavioral ecology Trends in Ecology and Evolution , pages 96-104 Feb. 2005 Fitzpatrick, Ben-Shahar, Smid, Vet, Robinson, Sokolowski. Additivity or dominance : the effect of one allele on another allele at the same genetic locus. - PowerPoint PPT Presentation

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Page 1: Announcements

Announcements

Page 2: Announcements

Candidate genes for behavioral ecologyTrends in Ecology and Evolution, pages 96-104 Feb. 2005Fitzpatrick, Ben-Shahar, Smid, Vet, Robinson, Sokolowski

Page 3: Announcements

Additivity or dominance: the effect of one allele on another allele at the same genetic locus.

Epistasis: the effect of one genetic locus on another independent locus.

Pleiotropy: the effect of a single gene or two or more phenotypic traits.

Polygenic: the effect of two or more genes on a single phenotypic trait.

Phenotypic plasticity: the interaction between genetic factors and the environment (e.g, norm of reaction).

Page 4: Announcements

Variation in gene sequence (polymorphisms, allelic differences)

atgtcagccgataactcattgatcgtaaattgagtttt

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Variation in gene expression(mRNA abundance)

Page 5: Announcements

High in foragers

(32)

High in nurses

(18)

Induced by methoprene

(249)13 0

Repressed by methoprene

(222)0 11

Treat with methoprene(JH analog)

Caged bees(no task-related

experiences)

Juvenile hormone analog (methoprene) accelerates the onset of foraging and causes forager-like changes in brain gene expression (in the absence of experience)

“marker” genes

Whitfield CW et al. PNAS. 2006. Oct 31; 103(44):16068-75.

Page 6: Announcements

Caged bees(no task-related

experiences)

Treat with QMP

High in foragers

(32)

High in nurses

(18)

Induced by QMP (602)

0 4

Repressed by QMP (704)

18 2

Queen mandibular pheromone (QMP) delays the onset of foraging and causes nurse-like changes in brain gene expression (in the absence of experience)

“marker” genes

Grozinger CM, Sharabash NM, Whitfield CW, Robinson GE. PNAS. 2003. Nov 25; 100:14519

Page 7: Announcements

Proximate studies: genetic variation for behavioral variation is maintained.

Ultimate studies: why is genetic variation maintained if selection usually acts to decrease variation!?!

Fitness benefits of genetic variants are not constant, but depend on environment, and the environment is variable?

Page 8: Announcements

Back to rovers and sitters.

Page 9: Announcements

Back to rovers and sitters – why are there two feeding strategies?

Hypothesis: Sitting is best strategy at low densities, while roving is best in high densities.

Test: Raise random sets of larvae in different environments and measure average movement after several generations.

Page 10: Announcements

Developmental flexibility

&

Developmental homeostasis

Proximate: What are they?

Ultimate: Why did they evolve?

Page 11: Announcements

Developmental flexibility: a change in the development & production of a behavior based on variation in environment.

Examples:learned behaviors, hormonal effects on behaviors, just about everything except behavioral differences due entirely to genetic differences!

Page 12: Announcements

Kin discrimination

The capacity of an individual to react differently to others based upon their degree of genetic relatedness.

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Kin discrimination

1) Social and aggressive behaviors: “associate with kin and be aggressive to nonkin”

2) Sexual behaviors: inbreeding avoidance - “associate (mate) with nonkin”

Page 14: Announcements

Learned kin discrimination: Imprinting

Paper wasps (Polistes) imprint on odors of nest & nestmates and are aggressive towards individuals with non-familiar odors.

nestmates non-nestmates

Page 15: Announcements

Learned kin discrimination: Phenotype Matching

(aka the “armpit effect”)

Compare a foreign phenotype to your own phenotype.

Page 16: Announcements

Learned kin discrimination: Phenotype Matching

(aka the “armpit effect”)

Compare a foreign phenotype to your own phenotype.

MHC alleles: Genes that function in immune response and are some of the most variable (# alleles) genes known.Basis for odor-based phenotype matching in fish, mice and humans.

Page 17: Announcements

Major Histocompatibility Complex (MHC).

MHC genes play a central role in immune recognition.

influence odors and mating preferences in vertebrates

MHC genes are among the most polymorphic loci:

1. There are a large number of alleles per locus (>100).

2. Large sequence divergence between alleles.

3. MHC allelic lineages are old (older than recent speciation events). So, for example, any given human MHC allele is more related to some alleles from chimpanzees and gorillas than it is to most other human alleles.

From W. Potts, U. Utah

Page 18: Announcements

Belding’s ground squirrels:

Sisters reared apart are less aggressive towards each other than other pairings.

Why are brother-sister pairings so aggressive?

Page 19: Announcements

Golden Hamsters:

Discriminate unfamiliar kin from familiar and unfamiliar non-kin

(work by Jill Mateo, University of Chicago)

Page 20: Announcements

Normal vs. cannibal forms in tiger salamanders

Individuals can develop as normal predatory larvae or switch over to a cannibal form.

Switch to cannibalism affected by:Population densitySize differencesDrying of water sourceGenetic relatedness to others

Page 21: Announcements

Innate kin discrimination: Genotype Matching

(aka the “green beard effect”)

term coined by Richard Dawkins

A gene gives individuals both a conspicuous trait (such as a green beard) and a tendency to act favorably to others with that same trait, mutual altruism between individuals could evolve (in the absence of kinship).

Dawkins “The Selfish Gene” 1976

Page 22: Announcements

Evidence for “green beards” in nature:

Different alleles for Gp-9 locus in fire ants influence whether workers will adopt or kill new queens.

Ross and Keller 1998. Selfish genes: a green beard in the red fire ant. Nature

Page 23: Announcements

Evidence for “green beards” in nature:

The csA gene in Dictyostelium discoideum promotes cell adhesion only for like genotypes.

Queller_et al. 2002. Single gene green beard effects in a social amoeba. Science

Page 24: Announcements

Developmental homeostasis:

Development of specific behaviors despite variation in environment

This category includes, but is not limited to innate behaviors

Page 25: Announcements

Rewiring the ferret brain

Despite having completely novel sensory inputs, the auditory cortex was able to develop into a functioning processing center for visual signals!

Page 26: Announcements

Developmental homeostasis within developmental flexibility!!

Normal predator Cannibal

Flexibility

homeostasis homeostasis

Page 27: Announcements

Why do developmental flexibility and homeostasis exist?

Flexibility can account for important, but variable environmental conditions, leading to increased fitness under different conditions.

Homeostasis reduces the chance of devastating developmental errors due to environmental deficits/changes

Page 28: Announcements

Evidence for ultimate benefits of developmental flexibility

Anolis lizards: morphology of hind legs changes when raised on large trunks or small branches.

Hypothesis: this flexibility leads to increased running performance in a specific environment.

Test: compare running speed/performance of lizards with different morphologies in both environments

Prediction: “trunk” morphology performs better on trunks while “branch” morphology performs better on branches

Page 29: Announcements

Evidence for ultimate benefits of developmental flexibility

Anolis lizards: morphology of hind legs changes when raised on large trunks or small branches.

Losos et al. 2002 Evolution

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Evidence for ultimate benefits of developmental homeostasis

Wolf spiders: smaller males in poorer condition tend to have more asymmetrical tufts on forelimbs

Hypothesis: females use tuft symmetry in mate choice as indicator of level of homeostasis

Test: digitally manipulate tuft asymmetry on videos of male wolf spiders courting females and measure female receptiveness.

Prediction: females will be more receptive to symmetrical males than asymmetrical males.

Page 31: Announcements

Evidence for ultimate benefits of developmental homeostasis

Wolf spiders: smaller males in poorer condition tend to have more asymmetrical tufts on forelimbs

Female spiders found video of control males more stimulating than asymmetrical males.

Uetz and Smith. 1999 Behavioral Ecology and Sociobiology

Why measure fluctuating asymmetry?

Page 32: Announcements

Directional asymmetryA pattern of bilateral variation due to developmental differences (predictable and subject to selection).

Page 33: Announcements

Has become a popular measure of ‘quality’, ‘stress’, ‘health’ or ‘fitness’

(e.g., increased stress experienced during development often yields increased fluctuating asymmetry)

However, its developmental origins remain obscure and are much debated.

Fluctuating asymmetryA pattern of bilateral variation where variation on the right and left sides is both random and independent.

It tends to be small (around 1% of trait size or less)

Page 34: Announcements

Environmental quality (FA is higher in poorer quality habitats)

Stress (stress during development increases FA)

Hybridization (FA is higher in hybrids between species)

Inbreeding (inbreeding increases FA)

Heterozygosity (FA decreases with increasing heterozygosity)

Mate Choice (females prefer more symmetrical males)

Page 35: Announcements

Facial Symmetry and Attractiveness

From Koehler et al. 2002

Low Symmetry

NormalHigh

SymmetryPerfect

Symmetry

Page 36: Announcements

Facial Symmetry and Attractiveness

• Evaluating original images and computer-generated composite images, participants rated faces in terms of attractiveness, dominance, sexiness and health.

• More symmetrical faces were given higher ratings.

• Male faces with larger features demonstrating male secondary sexual characteristics (large square jaw) were preferred by females.

From Grammer & Thornhill 1994

Randy Thornhill