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Adaptive Dynamics studying the dynamic change of community dynamical parameters through mutation and selection Hans (= J A J * ) Metz (formerly ADN ) IIASA.

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Presentation on theme: "Adaptive Dynamics studying the dynamic change of community dynamical parameters through mutation and selection Hans (= J A J * ) Metz (formerly ADN ) IIASA."— Presentation transcript:

1 Adaptive Dynamics studying the dynamic change of community dynamical parameters through mutation and selection Hans (= J A J * ) Metz (formerly ADN ) IIASA VEOLIA- Ecole Poly- technique & Mathematical Institute, Leiden University

2 preamble: some terminology  micro-evolution : changes in gene frequencies on a population dynamical time scale,  meso-evolution : evolutionary changes in the values of traits of representative individuals and concomitant patterns of taxonomic diversification (through multiple mutant substitutions),  macro-evolution : changes where one cannot even speak in terms of a fixed set of traits, like anatomical innovations. Goal: get a mathematical grip on meso-evolution.

3 function trajectories form trajectories genome development selection (darwinian) (causal) demography physics almost faithful reproduction ecology (causal) fitness environment components of the evolutionary mechanism

4 fitness function trajectories form trajectories genome development selection (darwinian) (causal) physics almost faithful reproduction ecology (causal) environment Adaptive Dynamics demography

5 AD’s basis in Commmunity Dynamics  Populations are considered as measures over a space ot i(ndividual)-states (e.g. spanned by age and size).  Environments ( E ) are delimited such that given their environment individuals are independent,  and hence their mean numbers have linear dynamics.  Resident populations are assumed to be so large that we can approximate their dynamics deterministically.  These resident populations influence the environment so that they do not grow out of bounds.  The resulting dynamical systems therefore have attractors, which are assumed to produce ergodic environments.

6 AD’s basis in Commmunity Dynamics  Mutants enter the population singly.  Therefore, initially their impact on the environment can be neglected.   The initial growth of a mutant population can be approximated with a branching process.  Invasion fitness is the (generalised) Malthusian parameter (= averaged long term exponential growth rate of the mean) of this proces:  (Existence guaranteed by the multiplicative ergodic theorem.)   Residents have fitness zero.

7 AD’s basis in Commmunity Dynamics resident population size population sizes of other species mutant population size fitness as dominant transversal eigenvalue

8 resident population size population sizes of other species mutant population size or, more generally, dominant transversal Lyapunov exponent AD’s basis in Commmunity Dynamics

9  Fitnesses are not given quantities, but depend on (1) the traits of the individuals, X, Y, (2) the environment in which they live:  (Y | E)  The latter is set by the resident community : E = E attr (C), C={X 1,...,X k ) biological implications Evolutionary progress is almost exclusively determined by the fitnesses of potential mutants.

10 AD: fitness landscapes change with evolution  Evolution proceeds through uphill movements in a fitness landscape that keeps changing so as to keep the fitness of the resident types at exactly zero.  Evolution proceeds through uphill movements in a fitness landscape resident trait value(s) x evolutionary time 0 0 0 fitness landscape:  (y,E(t)) mutant trait value y 0 0

11 type morph strategy trait vector point (in trait space) type morph strategy trait vector ( trait value) point (in trait space) effective synonyms

12 The different spaces that play a role in adaptive dynamics: the trait space in which their evolution takes place ( = parameter space of their i- and therefore of their p-dynamics ) = the ‘state space’ of their adaptive dynamics the physical space inhabited by the organisms the state space of their i(ndividual)-dynamics the space of the influences that they undergo ( fluctuations in light, temperature, food, enemies, conspecifics ): their ‘environment’ the parameter spaces of families of adaptive dynamics the state space of their p(opulation)-dynamics scaling up from organisms to trait evolution

13 the simplifications underlying AD essential for most conclusions i.e., separated population dynamical and mutational time scales: the population dynamics relaxes before the next mutant comes 1. mutation limited evolution 2. clonal reproduction 3. good local mixing 4. largish system sizes 5. “good” c (ommunity) -attractors 6. interior c-attractors unique 7. fitness smooth in traits 8. small mutational steps essential conceptuallly essential

14 from CD to AD: nature of the limits   ,  rescale time, only consider traits    rescale numbers to densities  = system size,  = mutations / birth t

15 the mechanism of meso-evolution C : = {X 1,..,X k } : trait values of the residents E nvironment: E attr (C) Y : trait value of mutant Fitness (rate of exponential growth in numbers) of mutant s C (Y) : =  ( E attr (C), Y) * Y has a positive probability to invade into a C community iff s C (Y) > 0. * After invasion, X i can be ousted by Y only if s X 1,.., Y,.., X k ( X i ) ≤ 0. * For small mutational steps Y takes over, except near so-called “ess”es.

16 population dynamics: branching process results or "grow exponentially” either go extinct, mutant populations starting from single individuals In an a priori given ergodic environment: (with a probability that to first order in | Y – X | is proportional to their (fitness) +, and with their fitness as rate parameter).

17 Invasion of a "good" c-attractor of X leads to a substitution such that this c-attractor is inherited by Y Y and up to O(  2 ), s Y (X) = – s X (Y). community dynamics: ousting the resident? Proposition: Let  = | Y – X | be sufficiently small, and let X not be close to an “evolutionarily singular strategy”, or to a c(ommunity)-dynamical bifurcation point. “ For small mutational steps invasion implies substitution.”

18 community dynamics: sketch of the proof When an equilibrium point or a limit cycle is invaded, the relative frequency p of Y satisfies = s X (Y) p(1-p) + O(  2 ), while the convergence of the dynamics of the total population densities occurs O(1). dp dt Singular strategies X* are defined by s X* (Y) = O (    ), instead of O(  ).

19 Near where the mutant trait value y equals the resident trait value x there is a degenerate transcritical bifurcation: community dynamics: the bifurcation structure

20 evolution will be towards increasing x evolution will be towards decreasing x Near where the mutant trait value y equals the resident trait value x there is a degenerate transcritical bifurcation: The effective speeds of evolutionary change are proportional to the probabilities that invading mutants survive the initial stochastic phase

21 population dynamics: the bifurcation structure probability that mutant invades evolution will be towards increasing x evolution will be towards decreasing x Near where the mutant equals the resident, the probability that the mutant invades changes as depicted below: The effective speeds of evolutionary change are proportional to the probabilities that invading mutants survive the initial stochastic phase

22 + + - y x - fitness contour plot x: resident y: potential mutant the graphical tools of AD trait value x x0x0 x1x1 x1x1 x2x2 x

23 X X 1 2 Mutual Invasibility Plot MIP y x trait value X x the graphical tools of AD + + - - Pairwise Invasibility Plot PIP

24 when does invasion imply substitution? protection boundary

25 trait value x Trait Evolution Plot TEP x2x2 the graphical tools of AD y x + + - - Pairwise Invasibility Plot PIP

26 evolutionarily singular strategies

27 (monomorphic) linearisation around y = x = x* c 11 +2c 10 +c 00 =0 a=0 b 1 +b 0 =0 neutrality of resident s u (u)= 0

28  local PIP classification

29  dimorphisms

30 dimorphic linearisation around y = x 1 = x 2 = x* Only directional derivatives (!)

31 population dynamics: non-genericity strikes

32 dimorphic linearisation around y = x 1 = x 2 = x* Only directional derivatives (!) : u 1 =uw 1, u 2 =uw 2

33 dimorphic linearisation around y = x 1 = x 2 = x*

34 local types of dimorphic evolution

35 local TEP classification

36 more about adaptive branching evolutionary time t i m e t r a i t fitness minimum population

37 beyond clonality: thwarting the Mendelian mixer assortativeness

38 a toy example Lotka-Volterra  all per capita growth rates are linear functions of the population densities Lotka-Volterra  all per capita growth rates are linear functions of the population densities LV models are unrealistic, but useful since they have explicit expressions for the invasion fitnesses.

39 a toy example viable range competition kernel carrying capacity width 1 –––––––– √2 

40 matryoshka galore isoclines correspond to loci of monomorphic singular points. interrupted : branching prone (  trimorphically repelling)

41 of two lines about to merge one goes extinct

42 matryoshka galore polymorphisms are invariant under permutation of indices X2X2 the six purple volumes should be identified ! adjacent purple volumes are mirror symmetric around a diagonal plane X1X1 X3X3

43 matryoshka galore the sets of trimorphisms connect to the isoclines of the dimorphisms isocline of species 1 isocline of species 3 X1X1 X2X2 X3X3 ( x 2 = x 3 )( x 2 = x 1 )

44 more consistency conditions!  There also exist various global consistency relations! The classification of the singular points was based on just a smoothness assumption and some ecologically reasonable consistency conditions. is extinct. the coexistence set one type. Use that on the boundaries of

45 a more complicated example

46 a potential difficulty: heteroclinic loops 1 2 1 2 33 ?

47 a potential difficulty: heteroclinic loops ? The larger the number of types, the larger the fraction of heteroclinic loops among the possible attractor structures !

48 much remains to be done! (Many partial results are floating around.)  Classify the geometries of the fitness landscapes, and coexistence sets near singular points in higher dimensions.  Develop a fullfledged bifurcation theory for AD.  Develop (more) global geometrical results.  Delineate to what extent, and in which manner, AD results stay intact for Mendelian populations.  Develop analogous theories for not fully smooth s-functions.  Analyse how to deal with the heteroclinic loop problem. (Some recent results by Odo and Barbara Boldin.)

49 The end


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