The study aimed to test whether fruit flies show greater altruism towards genetically identical individuals compared to unrelated individuals. The experiment involved rearing isogenic and unrelated fruit fly pairs and measuring their time spent at a food source. No significant differences were found between any of the groups. This suggests fruit flies do not exhibit preferential altruism based on genetic relatedness. The hypotheses that fruit flies would share more with identical flies was not supported.

1. Does Altruism Differ Between
Isogenic and Unrelated Fruit Flies?
Cigdem Demirez
Soham Bhatia
Bio318Y
http://www.littlebrownbooks.net/sedaris/
March.20.2012

2. Altruism, Kin Selection and
Indirect Fitness
• no study on Drosophila
•Altruism = sacrificial1
•Kin selection: favour relatives2
•Indirect fitness: benefits self
through relatives3 http://www.shutterstock.com/pic-14703082/stock-
photo-male-common-fruit-fly-drosophila-
melanogaster
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.

3. Drosophila melanogaster
•Wild type
-Isogeny: +; BB; +BB
•Sexually Dimorphic
-easy to differentiate sexes
•Short life cycle:
-20 to 30 days4
-can study many generations
Amsel, Sheri. www.exploringnature.org

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

5. Experimental Protocol
1- 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

6. 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.

7. 2- Experimental Trials
Isogenic Group: n=30 pairs of
- males
- females
•15 pairs for each strain
Unrelated Group: n=30 pairs of
- males
- females
Control Group: n=30 single
- males
- females

8. 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

9. 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

10. No difference in sharing between
genetically identical and unrelated flies
200
180
Avg Difference in Time
160
140
120
male
100 female
80
60
40
20
0
control isogenic unrelated

11. No significance in Values
Male Female
U = 538 U = 538
Isogenic vs Unrelated P = 0.207 P = 0.193
U = 470 U = 499
Isogenic vs Control P = 0.476 P = 0.312
U = 380 U = 407
Unrelated vs Control P = 0.225 P = 0.312
All p-values > α (0.05)
All U-values > Ucrit (317)

12. 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.

13. Why did our predictions fail?
1- No knowledge of the degree to how genetically
unrelated strains are
2- Variation in attraction to food
3- Spatial factor

14. 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

15. Conclusions
Drosophila not shown to share more with genetically
identical flies than unrelated flies
http://images.ask.com/fr?q=fruit+fly+i
n+lab&desturi=httpbwidth