Bio318 Final Presentationn

Does Altruism Differ Between Isogenic and Unrelated Fruit

Flies?

Cigdem DemirezSoham BhatiaBio318YMarch.20.2012http://www.littlebrownbooks.net/sedaris/

Altruism, Kin Selection and Indirect Fitness

• no study on Drosophila•Altruism = sacrificial1

•Kin selection: favour relatives2

•Indirect fitness: benefits self through relatives3

1- Kropotkin, Peter. (1902). Mutual Aid: A Factor of Evolution.2- Darwin, Charles. (1859). Origin of Species. 3- Hamilton, W.D. (1964). The Genetic Evolution of Social Behaviour. J. of Theo. Bio. 7 (1): 1-16.

http://www.shutterstock.com/pic-14703082/stock-photo-male-common-fruit-fly-drosophila-melanogaster

Drosophila melanogaster

Amsel, Sheri. www.exploringnature.org

•Wild type -Isogeny: +; BB; +BB

•Sexually Dimorphic -easy to differentiate sexes•Short life cycle: -20 to 30 days4 -can study many generations

Hypothesis: Fruit flies will show greater altruism in sharing food, if at all, towards genetically identical individuals (isogenic) than towards unrelated individuals.

Prediction: If Drosophila are altruistic, a pair of isogenic flies will statistically differ less in time spent at food source in comparison to an unrelated pair.

Do fruit flies share more with genetically identical versus unrelated flies, if at all?

Experimental Protocol1- Rear Flies

2- Experimental trials: 5 groups• pair of: isogenic males isogenic females unrelated males unrelated females•Control: single males & females 3- Record Measurements • time spent at food source within 5 minutes

1- Rearing Flies

Isogenic M Strain and C Strain

9 families each5

•Sucrose based food•21 ºC•12h light/dark cycle•Relatively humid

5-Simon, A.F. et. al. (2012). A simple assay to study social behaviour in Drosophila: measurement of social space within a group. Genes Brain and Behaviour. 11(2): 243-252.

2- Experimental Trials

Isogenic Group: n=30 pairs of - males - females

• 15 pairs for each strain Unrelated Group: n=30 pairs of - males - femalesControl Group: n=30 single - males - females

3- Measurement

•Food deprive for 24 h•Pair similar flies•Measure time spent at food source by each fly•5 minute trials•Time of day: 11 a.m. - 3 p.m.•Assumptions - each fly equally interested to feed

Analyzing Variables

•Independent variable: Categorical: -level of relatedness -gender•Response variable: Continuous: time spent at food source•Statistical Test:

non-parametric: Mann-Whitney U test

No difference in sharing between genetically identical and

unrelated flies

i u0

20

40

60

80

100

120

male female

Avg

Diff

eren

ce i

n Ti

me

Male Female

Isogenic vs UnrelatedU = 538 P = 0.207

U = 538P = 0.193

Isogenic vs ControlU = 470 P = 0.476

U = 499P = 0.312

Unrelated vs ControlU = 380 P = 0.225

U = 407P = 0.312

All p-values > α (0.05)All U-values > Ucrit (317)

No significance in Values

Conclusion: No difference in sharing between genetically identical and unrelated flies

Hypothesis: Fruit flies will show greater altruism in sharing food, if at all, towards genetically identical individuals (isogenic) than towards unrelated individuals.

Prediction: If Drosophila are altruistic, a pair of isogenic flies will statistically differ less in time spent at food source in comparison to an unrelated pair.

Why did our predictions fail?

1- No knowledge of the degree to how genetically unrelated strains are2- Variation in attraction to food 3- Spatial factor

Alternative Hypotheses

1- Flies do not have the sharing behaviour because they are genetically adapted to being exposed to ample food resources

2- Drosophila were not eating to conserve food

6- Kent, C. et. al. (2009). The Drosophila foraging gene mediates adult plasticity and gene-environment interactions in behaviour, metabolites and gene expression in response to food deprivation

Conclusions

Drosophila not shown to share more with genetically identical flies than unrelated

flies

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