Individual-based models of social evolution in biofilms

1. Individual-based models of social evolution in biofilms Sara Mitri @ the Foster lab Department of Zoology University of Oxford

2. Who am I? MSc thesis: “The co-evolution of language andbehaviourin robots” PhD thesis: “The evolution of communication in robot societies” Postdoc proposal: “Spatial patterns and social evolution in bacterial biofilms”

3. What questions am I interested in? General How does evolution shape social behaviour? How does evolution shape social behaviour in microbial biofilms? What role do ecological factors play in the evolution of social phenotypes in microbial biofilms? How does one combine theoretical and experimental methods to answer these questions? How do spatial patterns in microbial biofilms influence selection for social phenotypes? How does the presence of other species in microbial biofilms influence selection for social phenotypes? Specific

4. What technology do I use? Individual-based models Lab experiments

5. How do spatial patterns in microbial biofilms influence selection for social phenotypes?

7. Picioreanu et al. (2004) Appl & EnvMicrobiol Xavier et al. (2005) EnvMicrobiol

8. 1. Low nutrient concentration High nutrient concentration Nadell et al. (2010) PLoS Comp Biol

9. The thickness of the growing edge Nadell et al. (2010) PLoS Comp Biol

10. Secretes (costly) beneficial product Does not secrete beneficial product 2. Low nutrient concentration High nutrient concentration Nadell et al. (2010) PLoS Comp Biol

11. Experiments using Pseudomonas aeruginosa

12. How does the presence of other species in microbial biofilms influence selection for social phenotypes?

13. 1. “Towers” are no longer sufficient to give an advantage to secretors. 2. Other species can insulate secretors from non-secretors, giving them an advantage. Mitri et al. (in press) PNAS

14. 3. Mutualistic secretions seem unlikely to be selected for. Mitri et al. (in press) PNAS

15. Motivation Challenges Opportunities

16. Thanks go to… Carey Nadell Nuno Oliveira Jonas Schluter Marina Caldara João Xavier Wook Kim Kevin Foster

17. Experiments using Pseudomonas aeruginosa

19. One species Two species

20. One species Two species

21. Two species (species 2 benefits from secretions) Two species (species 2 does not benefit from secretions)

22. Two species (species 2 benefits from secretions) Two species (species 2 does not benefit from secretions)

23. Why do secretors do so badly in the presence of other species under low nutrient conditions? Hypothesis: competition during initial growth phase

24. Reducing competition

25. Reducing competition

26. 3 questions 1. How do secretors and non-secretors fare in the presence of other species? Secretors can be outcompeted by non-secretors due to increased initial competition.

27. 3 questions 2. How do secretors and non-secretors fare in the presence of many other species?

28. Species 2 is initially 9 times more abundant than species 1 Equal proportions of species 1 and 2

29. Species 2 is initially 9 times more abundant than species 1 Equal proportions of species 1 and 2

30. Why does the abundance of other species provide an advantage to secretors over non-secretors? Hypothesis: other species insulate secretors

31. Measuring segregation

32. 3 questions 2. How do secretors and non-secretors fare in the presence of many other species? Secretors can outcompete non-secretors when competition is low (e.g., high nutrients) because other species can separate the two phenotypes.

33. 3 questions 3. How do secretors and non-secretors fare if other species are mutualisticpartners?

34. Mutualism between 2 species with self-benefit Mutualism between 2 species without self-benefit

35. Mutualism between 2 species with self-benefit Mutualism between 2 species without self-benefit

36. Why does mutualism not work? Hypothesis: when cell types are segregated, secretors and species 2cannot benefit from each other; when cell types are mixed, non-secretors benefit

37. Explaining mutualism Low nutrients High nutrients Secretors Species 2 Non-secretors Species 2 Secretors Species 2 Non-secretors Species 2

38. Explaining mutualism

39. 3 questions 3. How do secretors and non-secretors fare if other species are mutualisticpartners? Secretors do not do well compared to non-secretors because conditions that favour mutualistic interactions also maximize benefits of non-secretors.

40. A case where mutualism “works”

41. A case where mutualism “works”

42. 3 questions 1. How do secretors and non-secretors fare in the presence of other species? 2. How do secretors and non-secretors fare in the presence of many other species? 3. How do secretors and non-secretors fare if other species are mutualisticpartners?

43. 3 answers Secretors can be outcompeted by non-secretors due to increased initial competition. Secretors can outcompete non-secretors when competition is low (e.g., high nutrients) because other species can separate the two phenotypes. Secretors do not do well compared to non-secretors because conditions that favour mutualistic interactions also maximize benefits of non-secretors.

44. Not taken into consideration (i.e. future work) By-product mutualisms Competition among groups Regulation of social behaviour Competition between species Niche overlap

45. Relative fitness of secretors to non-secretors