首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 78 毫秒
1.
Previous work has shown that mutation bias can direct evolutionary trends in genotypic space under strong selection and rare mutation. We present an extension of this work to general traits of the organism. We do this by allowing many different genotypes, with different fitnesses, to have the same trait value. This approach makes novel predictions and shows that the outcome of evolution for a trait is influenced by mutation bias as well as the fitness distribution of the genotypes that have the same trait value. This distribution can alter evolution in interesting ways, depending on the likelihood of generating high fitness mutants. We also show that mutation bias can direct evolution when many mutants are present at any one time. We demonstrate that mutation bias can drive long‐term evolutionary trends when the environment is constantly changing. Under biologically realistic conditions, we show that mutation bias can counter strong gradients of environmental selection over time. We conclude that evolutionary trends can be quite independent of the environment, even when they depress population fitness. Finally, we show that entropy can be a powerful source of mutation bias and can drive evolutionary trends. © 2015 Wiley Periodicals, Inc. Complexity 21: 331–345, 2016  相似文献   

2.
Most current photosynthesis research implicitly assumes that the photosynthetic process occurs only at one steady state. However, since the rate of each reaction in photosynthesis depends nonlinearly on its substrates and products, in theory, photosynthesis can have multiple steady states under given external conditions (i.e., in a given environment). The number of steady states of photosynthesis under the same external conditions has not been studied previously. Using the root finding program POLSYS_PLP [S.M. Wise, A.J. Sommese, L.T. Watson, Algorithm 801: POLSYS PLP: A partitioned linear product homotopy code for solving polynomial systems of equations, ACM Trans. Math. Software 26 (2000) 176–2000], we study the number of potential steady states of a simplified model of the Calvin cycle. Our results show that the simplified model of the Calvin cycle can reside in multiple steady states, but that only one of these is physiologically feasible. We discuss the results from an evolutionary perspective.  相似文献   

3.
对带两个趋化性参数的趋化性模型平衡解的存在性问题进行研究.在参数满足特定的条件下,应用局部分岔理论得到非常数平衡解的局部分岔结构,从而证明了该趋化性模型存在无穷多个非常数正平衡解.  相似文献   

4.
We are interested in the study of models describing the evolution of a polymorphic population with mutation and selection in the specific scales of the biological framework of adaptive dynamics. The population size is assumed to be large and the mutation rate small. We prove that under a good combination of these two scales, the population process is approximated in the long time scale of mutations by a Markov pure jump process describing the successive trait equilibria of the population. This process, which generalizes the so-called trait substitution sequence (TSS), is called polymorphic evolution sequence (PES). Then we introduce a scaling of the size of mutations and we study the PES in the limit of small mutations. From this study in the neighborhood of evolutionary singularities, we obtain a full mathematical justification of a heuristic criterion for the phenomenon of evolutionary branching. This phenomenon corresponds to the situation where the population, initially essentially single modal, is driven by the selective forces to divide into two separate subpopulations. To this end we finely analyze the asymptotic behavior of three-dimensional competitive Lotka?CVolterra systems.  相似文献   

5.
This paper is concerned with positive steady states for a diffusive predator–prey model with predator interference in a spatially heterogeneous environment. We first establish the necessary and sufficient conditions for the existence of positive steady states. In order to get a better understanding of the structure of positive steady states, we further investigate the asymptotic profiles of positive steady states as some parameter tends to zero or infinity.  相似文献   

6.
We biologically describe the phenomenon of the evasion of tumors from immune surveillance where tumor cells, initially constrained to exist in a microscopic steady state (MISS) elaborate strategies to evade from the immune control and to reach a macroscopic steady state (MASS). We, then, describe “evasion” as a long term loss of equilibrium in a framework of prey–predator-like models with adiabatic varying parameters, whose changes reflect the evolutionary adaptation of the tumor in a “hostile” environment by means of the elaboration of new strategies of survival. Similarities and differences between the present work and the interesting seminal paper [Kuznetsov VA, Knott GD. Modeling tumor regrowth and immunotherapy. Math Comput Model 2001;33:1275–87] are discussed. We also propose and study a model of clonal resistance to the immune control with slowly varying adaptive mutation parameter.  相似文献   

7.
A huge volume of research has been done for the simplest chemotaxis model (Keller–Segel's minimal model) and its variants, yet, some of the basic issues remain unresolved until now. For example, it is known that the minimal model has spiky steady states that can be used to model the important cell aggregation phenomenon, but the stability of monotone spiky steady states was not shown. In this paper, we derive, first formally and then rigorously, the asymptotic expansion of these monotone steady states, and then we use this fine information on the spike to prove its local asymptotic stability. Moreover, we obtain the uniqueness of such steady states. We expect that the new ideas and techniques for rigorous asymptotic expansion and spectrum analysis presented in this paper will be useful in attacking and hence stimulating research on other more sophisticated chemotaxis models.  相似文献   

8.
This article is concerned with bifurcations of steady states for a model system of phase separation, which is introduced by Eguchi–Oki–Matsumura (EOM). The system consists of coupled two evolution equations and admits steady state solutions with different energies. The bifurcation phenomena of these steady states with respect to the principal parameter, which is related to the temperature, are analyzed.  相似文献   

9.
An attempt is made to find a comprehensive mathematical framework in which to investigate the problems of well-posedness and asymptotic analysis for fully nonlinear evolutionary game theoretic models. The model should be rich enough to include all classical nonlinearities, e.g., Beverton–Holt or Ricker type. For several such models formulated on the space of integrable functions, it is known that as the variance of the payoff kernel becomes small the solution converges in the long term to a Dirac measure centered at the fittest strategy; thus the limit of the solution is not in the state space of integrable functions. Starting with the replicator–mutator equation and a generalized logistic equation as bases, a general model is formulated as a dynamical system on the state space of finite signed measures. Well-posedness is established, and then it is shown that by choosing appropriate payoff kernels this model includes all classical density models, both selection and mutation, and discrete and continuous strategy (trait) spaces.  相似文献   

10.
A dynamic model of the firm is studied in which investment costs depend on the magnitude of the investment relative to the stock of capital goods. It is shown that in general nonunique steady states can exist which can be stable or unstable. It is possible that unstable steady states occur in the concave domain of the Hamiltonian. For a particular specification, a scenario occurs with two stable steady states and one unstable steady state. The two stable steady states are long run equilibria; which one of them is reached in the long run depends on the initial state. In case the Hamiltonian is locally concave around the unstable steady state, this steady state is the threshold that separates the domain of initial conditions that each of the stable steady states attracts. The unstable steady state is a node and investment is a continuous function of the capital stock. If the unstable steady state lies in the nonconcave domain of the Hamiltonian, this steady state can either be a node or a focus. Furthermore, continuity can (but need not) be retained similarly to the concave case, a fact which has been entirely overlooked in the literature.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号