From genes to societies A biologist’s view on conflict and cooperation

1. From genes to societiesA biologist’s view on conflict and cooperation

2. Economic Game theory Oskar Morgenstern John Nash John von Neumann John von Neumann & Oskar Morgenstern (1944) Theory of Games and Economic Behavior

3. Evolutionary Game theory • Maynard Smith (1986) Evolution and the Theory of Games • Applied logic of economic game theory to biological systems • Blind process of natural selection no longer required rationality assumption • “Let nature do the work and see what happens” • Outcome was as if agents were rational, self-interested fitness maximizers

4. Evolutionarily stable strategy (ESS) wild type rare mutant x x mutation mutation x x reproduction reproduction selection selection does better than is not an ESS cannot invade is an ESS

5. and may also end up coexisting in the population in some equilibrium frequency occurs at the point where they have equal fitness such a stable polymorphic state is an evolutionary stable state Evolutionary stable state Maynard Smith 1986 Evolution and the Theory of Games

6. Example: hawk-dove game • Two types: hawks and doves • Doves share a resource peacefully, hawks fight over it • B=value of the resource, C=cost of fighting another hawk • Result: • ESS is to play hawk with probability B/C • or evolutionary stable state with fraction B/C hawks Individual 2 dovehawk dove Individual 1 hawk Maynard Smith & Price Nature 1973 The Logic of Animal Conflict

7. Strategists can be genes, cells, organisms or societies Maynard-Smith, J., Szathmary, E. 1995. The major transitions in evolution. Cambridge UP. Independent replicators Linked replicators in single cell Multicellular organisms Societies

8. Plan of my talk • Illustrate biological conflicts at various levels • What causes the conflicts? …why do evolutionary interests differ • How are conflicts resolved? …how can wasteful conflict be prevented • Can we apply this sort of thinking to humans?

9. Richard Dawkins

10. Handy shortcuts • “An organism should want to do this or that”means “A gene that makes it do that should spread” • “The interests are for it to…”means“That’s it’s ESS” • does not imply any moral judgement

11. 1. Conflicts in the genome

12. The basis for the conflict (1) • Mendel’s first law:genetic variants segregate and randomly reunite • Means that 2 genes at a locus should have equal chances of being passed on • But any gene would do better if it would be transmitted to more than ½ of the gametes • I.e. there is a conflict between two genes at a locus

13. Peacock et al. 1972

14. Genes that beat Mendel’s laws Normal SD in fruit fly w = wild type D = distorter w w w D w w w D Sperm Production

15. Genes that beat Mendel’s laws Normal SD in fruit fly t in the mouse w = wild type D = distorter w w w w D D w w w w D D Sperm Production Copulation w w w D D Inside Female

16. The basis for the conflict (2) Nuclear genesinherited from mother + fathertransmitted through both sexes equally Leda Cosmides & John ToobyCytoplasmic inheritance and intragenomic conflict 1981 J. Theor. Biol. Mitochondrial genesancient bacteria (ca. 2 BY BP) maternally inheritedtransmitted through females onlymale=dead end

17. Evidence • ca. 4% of all hermaphrodite plants carry mitochondrial gene resulting in male sterility • no pollen, but increased seed production • nuclear genes may restore male sterility Saumitou-Laprade et al. 1994

18. Wolbachia bacteria • Kill all males 2. Turn males into females 3. Make males unnecessary Infects reproductive tissues of insects and arthropods Only maternally transmitted Benefit production of females at the expense of males O’Neill et al. 1999 Influential Passengers

19. Conflict 3: jumping genes • transposons can “jump” from one place to another in the genome (cut and paste) • make up 10% of our genome • serve no useful purpose

20. What resolves the conflict? • Organisms usually seem to functionreasonably well. Why? • Egbert Leigh (1977) Proc.Natl.Acad.Sci. USA • Parliament of the genes • Selfish genes frequently cause cost towhole organism • Hence genes at other loci are selectedto suppress the effect of selfish genes • Causes conflicts to be resolved in favour of collective interests

21. 2. Conflicts in the family

22. Kin selection • Hamilton’s rule (J. Theor. Biol. 1964) • JBS Haldane • “I would be willing to lay down my life for 2 brothers or 8 cousins.” • r to offspring = ½ : you should love your children Cost to actor Benefit to receiver Relatedness

23. Basis for the conflict • Robert Trivers (1974) • Mother equally related to all offspring (r=0.5) • But offspring value themselves (r=1) more than siblings (r=0.5) • Consequence: sibling conflict + parent-offspring conflict Trivers Am. Zool. 1974

24. Siblicide Spadefoot toads Sand tiger sharksPiglets Masked boobyKittiwake gulls Indian rosewood

25. How is the conflict resolved? Briskie et al. 1994 • High relatednesspasserine birds: chicks beg lesswhen they are more related9-banded armadillo: clonal offspring • Parental discipliningpossible because of power asymmetrymay be costly in itselfblue footed booby vs. masked booby Lougheed & Anderson 1998

26. 3. Conflicts in superfamiliesInsect societies

27. SOCIAL INSECTSCOOPERATE

28. But there should also be conflict • William D. Hamilton "The Genetical Evolution of Social Behaviour" (1964, J. Theor. Biol.) • Robert Trivers & Hope Hare “Haplodiploidy and the Evolution of Social Insects" (1976, Science) Kin selection theoryIndividuals are selected to help kin but be nasty towards nonkin Relatedness asymmetries in social insectcolonies should lead to a variety ofconflicts

29. Conflict 1 BENEFIT COST WORK increased colony efficiency no direct reproduction REPRODUCEobtain direct reproductionreduced colony efficiency(laying workers do not work) Wenseleers, Helantera & Ratnieks 2004 J. Evol. Biol.; Wenseleers et al. 2004 Am. Nat.

30. Ratnieks & Visscher Nature 1989

31. 20 Polistes chinensis 15 Dolichovespula saxonica level of selfishness (% of reproductive workers) Vespula rufa 10 D. sylvestris D. norwegica D. media 5 Vespa crabro Vespula vulgaris 0 Apis mellifera Spearman rank R = -0.92, p = 0.0005 60 70 80 90 100 effectiveness of policing (%)

32. 2.0 36 n=68 species ANTS 9 33,37,43 8 BEES WASPS 7 56 52 35 1.5 34 POLICING Workers most relatedto queen’s sons NO POLICING Workers most relatedto other workers’ sons 59 55 28 41 26 65 10 60 Log10(% males workers' sons+1) 1.0 58 30 25 31 29 4 6 61 5 0.5 50 1 39 51 63 3,15-20,32,3840,42,44-47 53-54,68 21 14 12 62 2 49 48 66 24 57 27 13 70 67 69 64 11 0.0 22-23 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 relatedness to workers' vs. queen's sons Wenseleers & Ratnieks 2005

33. Conflict 2 female larva BENEFIT COST BECOME WORKER increased colony efficiency less direct reproduction BECOME QUEENgreater direct reproductionreduced colony efficiency(queen overproduction) Wenseleers et al. J. Evol. Biol. 2003; Ratnieks & Wenseleers Science 2005

34. The struggle to become a queen Q Melipona stingless beesca. 20% become queenmatches predicted ESS almost perfectly Q Q Q Q Ratnieks & Wenseleers Science 2005

35. Conflict very costly: queens killed Wenseleers et al. 2003, 2004

36. Honeybee: worker fate enforced “Power” to the adult workers

37. How are conflicts in insect societies resolved? • High relatednessmay limit conflict, but only partially effective • Mechanisms of coerciongood for the colony…but not so nice for the oppressed individuals Ratnieks, Foster & Wenseleers 2006 Ann. Rev. Entomol.

38. 4. Sexual conflictsThe battle of the sexes

39. Male-male competition (1)

40. Male-male competition (2) • Abele, L.G. and S. Gilchrist. 1977. Homosexual rape and sexual selection in acanthocephalan worms. Science

41. Battle between the sexes (1) • When is there a conflict-of-interest between the sexes? • Males ensure paternity by causing harm to females

42. Bean beetle males harm females Crudgington & Siva-Jothy Nature 2000

43. Seminal toxins in the fruit fly • Male injects female with toxin Sedates female and prevents her from mating with other males • But costly to female: shortens her lifespan Chapman et al. Nature 1995

44. Battle between the sexes (2) • When is there a conflict-of-interest between the sexes? • Males ensure paternity by causing harm to females • Conflict over sex roleschoosiness, parental invesment

45. Conflict over sex roles Typical sex roles come about because of differences between the sexes in investment in individual offspring FEMALES Invest a lot in each offspring (eggs, gestation, lactation, care) Cannot have large numbers of offspring Cannot greatly increase fitness by having multiple partners Usually can increase fitness by being choosy MALES Invest little in each offspring Can have large numbers of offspring Can greatly increase fitness by having multiple partners Rarely can increase fitness by being choosy

46. Angus John Bateman Robert Trivers

47. Eager males and choosy females • # fertilisable females < sexually active males (♂-biased operational sex-ratio) • selects for “eager” males and “choosy” females • males should frequently want to mate with females when they don’t want to • females should reject low-quality males

48. Coercive sex Not enforced Long courtship Enforced No courtshipStruggle Iron cross blister beetle Alcock 2000

49. Female counterdefence • Dunnocks: eject sperm of low-status males Davies Nature 1983

50. water striders Sexual arms race n=15 species Arnqvist & Rowe Nature 2002