Persistence and fluctuation of lateral dimorphism of fishes

1. Persistence and fluctuation of lateral dimorphism of fishes Prof.Shirakihara M.Nakajima lived in Switzerland Mifuyu Nakajima, Hiroyuki Matsuda and Michio Hori, in submission K.Morita M.Mori U.CateTown M.Kai

2. back back Lateral dimorphism of scale eating cichlids in Lake Tanganyika Hori 1991 Science 267 Righty Lefty

3. Overview • What is predator specific defense? • What is antisymmetric predation? • Is laterality frequency really fluctuate? • If so, what is mechanism of fuluctation?

4. predator 3 prey 2 1 plant Prey is not solely victim, but has antipredator traits. • Vigilance, Schooling, Refuge, • There may be a trade-off between antipredator effort and other fitness component (e.g., foraging time)

5. Antipredator effort against predator 1 is … • [Nonspecific defense] effective against both predator species (types) 1 & 2; • [Partly-specific] partly effective against 2; • [Perfect-specific] not effective against 2 at all; • [overly-specific] riskier against 2 than when it pais no attention to any predator.

6. Increase predator 2 2 Increase vigilance Decrease predator 3 3 Antipredator trait-mediated Exploitative Competition 2 3 1

7. Increase predator 2 2 3 Watch more against 2 Increase predator 3 Exploitative Mutualism(Matsuda, Abrams, Hori. Oikos 1993, 68:549-559) 2 3 1

8. How many points can you watch for simultaneously? Quiz by Japan Automobile Fedaration JAF News, the recent issue

9. Increase prey 2 1 Increase predator Decrease prey 3 2 3 Apparent Competition(Holt, 1979) 1 2 3

10. Increase prey 2 1 Predator focuses on prey 2 Increase prey 3 2 3 Apparent mutualism(Abrams & Matsuda 1996 Ecology 77:610-616) 1 2 3

11. Predator-specific defense enhances • Coexistence of predators. • A more complex community strucutre Food web in Lake Tanganyika Matsuda with Abrams & Hori (1994, 1996, Evol. Ecol)

12. Coexistence of laterality dimorphism (antisymmetry) Scale eaters in Lake Tanganyika (Hori unpublished) Frequencies of lefties Year of birth

13. Overview • What is predator specific defense? • What is antisymmetric predation? • Is laterality frequency really fluctuate? • If so, what is mechanism of fuluctation?

14. “Antisymmetry” Fluctuating asymmetry (FA) Directive asymmetry (DA) Three types of Asymmetries(van Valen 1962)  

15. Antisymmetry in fishes • Scale-eating cichlid in Lake Tanganyika • Lefties feed on scales of the left side, righties feed on scales of the right side • Frequency dependent natural selection • Hori 1991 Science 267: • Maintained by predator-specific defense

16. Antisymmetry Mud Fiddler Crabs (Uca pugnax) have antisymmetry in pincers http://www.assateague.com/mud-cr.html • Bimodal distribution of laterality in crabs, snails, … • Maintained by sexual selection • Few reports of antisymmetry maintained by predation

17. More Story in Fish Laterality…. • Another Tanganyikan fish has lateral asymmetry (Mboko et al. 1998: Zool. Sci. 15) • A fresh water goby has lateral asymmetry in a Japanese river(Seki et al. 2000: Zool. Sci. 17) • Many fishes and other aquatic invertebrates have lateral antisymmetry! (Hori unpublished) • In these fishes, lefty is dominant heritage. • Far too counterintuitive! • We need more evidence and theoretical reason...

18. Righty predators eat lefty prey, and vice versa. • Lefties of scale-eating fish feed only on left side scales of lefties, righties feed only on right side scales of righties (Hori 1993 stomach contents, unpublished lab experiment). • Circa 75% of the stomach contents of righty and lefty piscivorous predators (Lamprologus spp.) were the lefty and righty, respectively (Hori unpublished field data).

19. Is evidence still short? Hori et al. (unpublished field data)

20. Why does a lefty catch a righty?(Michio Hori’s idea)

21. Definition of Antisymmetric Predation • Both prey and predator have anti-symmetric traits (laterality); • “Lefty” predators feed on “righty” prey; “Righty” predators feed on “lefty” prey.

22. Overview • What is predator specific defense? • What is antisymmetric predation? • Is laterality frequency really fluctuate? • If so, what is mechanism of fuluctation?

23. Question… %lefties • Does it really fluctuate? • Statistically significant (Hori unpubl) • Does it really synchronize? • If so, what mechanism promote fluctuation?

24. Is evidence still short? • If frequency fluctuates, this is non-random sampling over several years. • This is an evidence for either • Existence of antisymmetric predation or • Existence of laterality frequency fluctuation Hori et al. (unpublished field data)

25. Two-platoon lineups in MLB No fluctuation is reported in the frequency of lefty pitchers and batters in MLB or College baseball

26. Our hypothesis for laterality fluctuation Persistence and fluctuation in lateral antisymmetry is • Maintained by Antisymmetric Predation, in analogy to Predator-specific defense

27. A two-trophic level system yL yR K zL zR

28. Lyapunov-type function of the symmetric 4 “population” system • Trajectories converge the “line” zL+ zR=2c/Bm (constant). < 0

29. Increase Lefty Predators Decreasing righty prey = Increasing lefty prey yL yR Laterality frequency fluctuation mediated by antisymmetric predation zL zR predator Frequencies of lefties prey time

30. The system always has a neutrally stable equilibrium & cyclic orbits with any amplitude. Predator xR % Rigties Righty Prey zR time A = B = C = 1, r = 1, K=10, m=0.8, d=0.05, c=0.15 Lefty Any modification makes it stable or unstable.

31. Omnivory is common in Lake Tanganyika Fish Community Piscivores Scale eaters Hori 1997 Algal eaters

32. x y z Extension to Holt and Polis (1997) • Where k = K/2

33. 6 “populations” (3 sp.×{Lefty, Righty} X: scale eaters Y: piscivores Z: algal feeders X preys on both y and z. Three trophic levels xL xR yL yR zL zR

34. if X is omnivory, lefties increase Does omnivory destabilize or stabilize the antisymmetric predation system? Righties increase Lefties increase Righties increase

35. Transition diagram ?

36. Invasibility analysis xR yL dxR/dt/xR >0 if xR is invasible

37. Asymmetric equilibrium is always invasible. ② ③ ④ A ⑤ ① B Axy=1 m=0.8 K=5 r=1 c=0.5 d=0.5

38. For lefties (asexual reproduction model) 6 “population” dynamic model Prey on zR Prey on yR Preyed by xR Prey on zR

39. Population genetic model (1-locus-2-alleles) Righties： allele a: gene frequency pi Lefties： allele A: gene frequency 1-pi fx = m Axy Ny (1-py2) + m AxzNz(1-pz2) – c

40. Equilibrium gene frequency  Phenotypic frequency: From local stability analysis, this is always an unstable focus. b0 b0b1-b2 < 0

41. % Righties time Simulation exhibits a stable limit cycle. y x z A=1.3 B=0.25 C=1 m=0.8 K=5 r=1 c=0.5 d=0.5 It qualitatively explains the field observation.

42. We must apply our model to the entire community (Hori unpublished)

43. Our model results • Under the perfect anti-symmetric predation, no force (“friction”) to stabilize a 1:1 laterality ratio exists. • Omnivory destabilizes 1:1 laterality ratio and enhances a stable limit cycle (coexistence with fluctuation). • Nakajima, Matsuda, Hori (in review)

44. Why did laterality evolve? • Scale-eaters first evolved laterality, because they attack either side scales. • “Prey” needed to evolve laterality to improve predator-specific defense • …What story is possible in the absence of scale-eaters??? • Measure quantitative trait in laterality I don’t know

45. Lateral dimorphism is Single-locus Mendellian inheritance Seen in most of fishes (Hori unpubl) Maintained by antisymmetric predation Fluctuation & coexistence in omnivory [Overly?] predator-specific defense This is a new story of Antisymmetry

46. Competitive exclusion of laterality in amino acids L-amino acids D-amino acids Omnivory is probably important for coexistence