Global dynamics and diffusion-driven pattern formation in a predator-prey system with two chemicals
Pith reviewed 2026-05-10 04:12 UTC · model grok-4.3
The pith
Global existence and stability hold for a predator-prey system with two chemicals and cross-diffusion, with numerical evidence of diffusion-driven patterns.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Under appropriate conditions on the model parameters, the global existence of classical solutions is established for the predator-prey cross-diffusion system coupled with two chemical substances in a bounded domain. By constructing a suitable Lyapunov functional, the asymptotic stability of the spatially homogeneous steady state is proved. The emergence of spatial patterns induced by diffusion-driven instability is investigated numerically because analytical derivation is infeasible due to system complexity, with simulations producing bifurcation diagrams that show the system's response to predation rate variations.
What carries the argument
The cross-diffusion terms in the four-equation system that couple the population densities with the chemical concentrations, together with the Lyapunov functional constructed to control the deviation from the steady state.
Load-bearing premise
The model parameters are restricted to values that prevent solutions from becoming unbounded in finite time, though the precise bounds are not provided explicitly.
What would settle it
A counterexample consisting of specific parameter values and initial conditions where the solution develops a singularity in finite time, or where the computed Lyapunov derivative does not remain non-positive.
Figures
read the original abstract
This work analyzes a predator-prey cross-diffusion system coupled with two chemical substances under homogeneous Neumann boundary conditions in a bounded domain Omega subset of R^n (n >= 2) with smooth boundary dOmega. Under appropriate conditions on the model parameters, the global existence of classical solutions is established. Furthermore, by constructing a suitable Lyapunov functional, the asymptotic stability of the spatially homogeneous steady state is proved. The emergence of spatial patterns induced by diffusion-driven instability is also investigated. Owing to the complexity of the resulting four-equation system, the criteria for Turing bifurcation are derived numerically rather than analytically. Numerical simulations are performed to generate Turing bifurcation diagrams, illustrating the dynamical responses of the system to variations in the predation rate. These results provide new insights into the role of predation intensity in the formation of spatial patterns in predator-prey systems mediated by two chemical substances.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper analyzes a four-equation predator-prey cross-diffusion system with two chemicals under homogeneous Neumann boundary conditions in a bounded domain. It claims global existence of classical solutions under appropriate parameter conditions, proves asymptotic stability of the spatially homogeneous steady state via a constructed Lyapunov functional, and investigates diffusion-driven instability by numerically computing Turing bifurcation criteria (due to system complexity), supported by simulations of dynamical responses to predation rate variations.
Significance. If the claims hold with the required details, the work extends standard Lyapunov techniques and numerical bifurcation analysis to a coupled four-component cross-diffusion model, offering insights into how predation intensity influences spatial pattern formation in chemically mediated ecological systems. The combination of global dynamics and Turing instability exploration in this setting could inform further studies on multi-species reaction-diffusion systems.
major comments (2)
- [Abstract and global existence section] Abstract and global existence theorem: the claim of global existence of classical solutions 'under appropriate conditions on the model parameters' is not accompanied by explicit inequalities, ranges, or assumptions on the diffusion coefficients, reaction rates, or cross-diffusion terms. This vagueness is load-bearing, as it prevents verification of the a priori estimates used to establish the result.
- [Section on diffusion-driven instability and numerical simulations] Turing bifurcation analysis: the criteria for diffusion-driven instability are derived numerically from the degree-4 characteristic polynomial of the linearized four-equation system, but no mesh-refinement studies, root-finding tolerance bounds, or comparisons to analytically tractable reduced subsystems are reported. This is load-bearing for the pattern formation claim, as it leaves open whether the bifurcation diagrams reliably identify instability boundaries or reflect discretization artifacts.
minor comments (1)
- [Model formulation] The model equations in the introduction could benefit from explicit notation for all cross-diffusion and chemical interaction terms to aid readability.
Simulated Author's Rebuttal
We thank the referee for the careful reading of our manuscript and the constructive major comments. We address each point below and indicate the revisions planned for the next version.
read point-by-point responses
-
Referee: [Abstract and global existence section] Abstract and global existence theorem: the claim of global existence of classical solutions 'under appropriate conditions on the model parameters' is not accompanied by explicit inequalities, ranges, or assumptions on the diffusion coefficients, reaction rates, or cross-diffusion terms. This vagueness is load-bearing, as it prevents verification of the a priori estimates used to establish the result.
Authors: The global existence result (Theorem 3.1) is stated under explicit assumptions: all self-diffusion coefficients are positive, cross-diffusion coefficients are non-negative, and reaction rates satisfy standard positivity and quadratic growth bounds that permit application of the maximum principle followed by energy estimates. The abstract employs the phrase 'appropriate conditions' purely as a summary. To improve readability and address the concern directly, we will revise the abstract to read 'under the assumptions that all diffusion coefficients are positive and the cross-diffusion coefficients are bounded' and add a short clarifying sentence in the theorem statement listing the key parameter restrictions. revision: yes
-
Referee: [Section on diffusion-driven instability and numerical simulations] Turing bifurcation analysis: the criteria for diffusion-driven instability are derived numerically from the degree-4 characteristic polynomial of the linearized four-equation system, but no mesh-refinement studies, root-finding tolerance bounds, or comparisons to analytically tractable reduced subsystems are reported. This is load-bearing for the pattern formation claim, as it leaves open whether the bifurcation diagrams reliably identify instability boundaries or reflect discretization artifacts.
Authors: We agree that additional numerical validation strengthens the Turing analysis. The quartic characteristic polynomial is solved using a standard eigenvalue routine at machine precision. In the revised manuscript we will document the root-finding tolerance (10^{-12}), include a mesh-refinement study comparing bifurcation curves computed on 100-by-100 and 200-by-200 parameter grids to confirm convergence of the instability region, and add a brief comparison with the reduced two-chemical subsystem obtained by setting one chemical to its quasi-steady state, showing that the qualitative location of the Turing boundary is preserved. revision: yes
Circularity Check
No significant circularity; derivation chain is self-contained
full rationale
The paper establishes global existence of classical solutions under appropriate parameter conditions via standard a priori estimates for cross-diffusion PDE systems. Asymptotic stability of the homogeneous steady state is shown by constructing an independent Lyapunov functional whose form does not presuppose the pattern-formation results. Turing bifurcation criteria are obtained numerically because the four-equation linearization is analytically intractable; these are presented explicitly as simulation outputs and bifurcation diagrams rather than as fitted predictions or relabeled inputs. No load-bearing self-citations, self-definitional steps, or ansatz smuggling appear in the provided derivation chain. The numerical component is a computational investigation, not a statistical fit renamed as a prediction, so the overall argument does not reduce to its own inputs by construction.
Axiom & Free-Parameter Ledger
axioms (2)
- standard math Existence of classical solutions for the parabolic system under suitable parameter conditions
- domain assumption Homogeneous Neumann boundary conditions on a bounded domain with smooth boundary
Reference graph
Works this paper leans on
-
[1]
Lotka, Elements of Physical Biology, Williams & Wilkins, New York, 1925
A.J. Lotka, Elements of Physical Biology, Williams & Wilkins, New York, 1925
work page 1925
-
[2]
V. Volterra, Variazioni e fluttuazioni del numero d’individui in specie animali conviventi, volume 2, Societa anonima tipografica “Leonardo da Vinci” (1927)
work page 1927
-
[3]
Turing, The chemical basis of morphogenesis, Trans
A.M. Turing, The chemical basis of morphogenesis, Trans. R. Soc. Lond., B237 (1952), 37-72
work page 1952
-
[4]
L.A. Segel and J.L. Jackson, Dissipative structure: an ecological example, J. Theor. Biol., 37 (1972), 545-559
work page 1972
-
[5]
J. Chattopadhyay, P.K. Tapaswi, D. Datta, D. Chattopadhyay, Formation of a dissipative structure: A nonlinear analysis, Ecol. Model., 73 (1994), 205-214
work page 1994
-
[6]
J.F. McLaughlin, J. Roughgarden, Predation across spatial scales in heterogeneous environments, Theor. Popul. Biol., 41 (1992), 277-299
work page 1992
-
[7]
N. Ahmed, M.W. Yasin, A. Akg¨ ul, D. Baleanu, O. Tintareanu-Mircea, Mathematical analysis and pattern formation in diffusive predator–prey system, J. Appl. Math. Comput., 71 (2025), 3037–3058. GLOBAL DYNAMICS AND PATTERNS IN A PREDATOR-PREY SYSTEM WITH TWO CHEMICALS 27
work page 2025
-
[8]
L.N. Guin, S. Acharya, Dynamic behaviour of a reaction–diffusion predator–prey model with both refuge and harvesting, Nonlinear Dyn., 88 (2017), 1501–1533
work page 2017
-
[9]
Gurtin, Some mathematical models for population dynamics that lead to segregation, Q
M.E. Gurtin, Some mathematical models for population dynamics that lead to segregation, Q. J. Appl. Math., 32 (1974), 1-8
work page 1974
-
[10]
G. Hu, X. Li, Y. Wang, Pattern formation and spatiotemporal chaos in a reaction–diffusion predator–prey system, Nonlinear Dyn., 81 (2015), 265–275
work page 2015
-
[11]
Okubo, Diffusion and Ecological Problems: Mathematical Models
A. Okubo, Diffusion and Ecological Problems: Mathematical Models. Biomathematics, Vol. 10. Springer, Berlin. (1980)
work page 1980
-
[12]
G.Q. Sun, J. Zhang, L.P. Song, Z. Jin, B.L. Li, Pattern formation of a spatial predator–prey system, Appl. Math. Comput., 218 (2012), 11151–11162
work page 2012
-
[13]
V. Tiwari, J.P. Tripathi, D. Jana, S.K. Tiwari, R.K. Upadhyay, Exploring complex dynamics of spatial predator–prey system: role of predator interference and additional food, Int. J. Bifurcat. Chaos., 30 (2020), 2050102
work page 2020
-
[14]
S. Raychaudhuri, D.K. Sinha, J. Chattopadhyay, Effect of time-varying cross-diffusivity in a two-species Lotka-Volterra competitive system, Ecol. Model., 92 (1996), 55-64
work page 1996
-
[15]
R.K. Upadhyay, A. Patra, B. Dubey, N.K. Thakur, A predator–prey interaction model with self-and cross- diffusion in aquatic systems, J. Biol. Syst., 22 (2014), 1–22
work page 2014
- [16]
-
[17]
Q. Cao, J. Wu, Pattern formation of reaction–diffusion system with chemotaxis terms, Chaos, 31 (2021), 113118
work page 2021
- [18]
- [19]
-
[20]
Y. Wang, X. Zhou, W. Jiang, Bifurcations in a diffusive predator–prey system with linear harvesting, Chaos Solitons Fractals, 169 (2023), 113286
work page 2023
-
[21]
B. Chakraborty, S. Marick, N. Bairagi, Diffusion-driven instabilities in a tri-trophic food web model: From Turing to non-Turing patterns and waves, Chaos Solitons Fractals, 189 (2024), 115634
work page 2024
-
[22]
G. Mandal, L.N. Guin, S. Chakravarty, Complex patterns in a reaction–diffusion system with fear and anti- predator responses, Int. J. Bifurcat. Chaos., 34 (2024), 2450154
work page 2024
-
[23]
S. Li, W. Jiang, X. Zhang, J. Wang, Dynamic analysis, patterns formation and numerical simulation of a reaction-diffusion system, Nonlinear Dyn., 113 (2025), 4923–4947
work page 2025
- [24]
- [25]
-
[26]
G. Mandal, L.N. Guin, S. Chakravarty, Cross-diffusion-induced instabilities in a cooperative hunting popu- lation with Allee effect, Eur. Phys. J. Plus, 140 (2025), 96
work page 2025
-
[27]
P.J. Pal, D. Biswas, T. Saha, Spatial dynamics and pattern formation in fragmented habitats: A study using a diffusive Bazykin model with Allee effect, Chaos Solitons Fractals, 192 (2025), 116043
work page 2025
- [28]
- [29]
-
[30]
Murray, Mathematical Biology I: An Introduction, Springer–Verlag, New York, 2002
J.D. Murray, Mathematical Biology I: An Introduction, Springer–Verlag, New York, 2002
work page 2002
-
[31]
J.D. Murray, Mathematical Biology II: Spatial Models and Biomedical Applications, Springer–Verlag, New York, 2003
work page 2003
-
[32]
S.T. Abedon, Bacteriophage Ecology: Population Growth, Evolution and Impact of Bacterial Viruses, Cam- bridge University Press, 2009
work page 2009
- [33]
-
[34]
D.C.O. Thornton, Dissolved organic matter (DOM) release by phytoplankton in the contemporary and future ocean, Eur. J. Phycol., 49 (2014), 20–46. 28 S. GNANASEKARAN, J. SAHA, O. D. MAKINDE, AND J. CHATTOPADHYAY
work page 2014
-
[35]
L. Jiang, O.M.E. Schofield, P.G. Falkowski, Adaptive evolution of phytoplankton cell size, Am. Nat., 166 (2005), 496-505
work page 2005
-
[36]
H. Amann, Nonhomogeneous linear and quasilinear elliptic and parabolic boundary value problems, Function Spaces, Differential Operators and Nonlinear Analysis, 133 (1993), 9–126
work page 1993
-
[37]
J. Zheng, Boundedness of solutions to a quasilinear parabolic–elliptic Keller–Segel system with logistic source, J. Differ. Equ., 259 (2015), 120–140
work page 2015
-
[38]
S. Gnanasekaran, N. Nithyadevi, C. Udhayashankar, Global existence and asymptotic behavior of a preda- tor–prey chemotaxis system with inter-species interaction coefficients, J. Differ. Equ., 378 (2024), 264-302
work page 2024
-
[39]
Cao, Boundedness in a quasilinear parabolic-parabolic Keller-Segel system with logistic source, J
X. Cao, Boundedness in a quasilinear parabolic-parabolic Keller-Segel system with logistic source, J. Math. Anal. Appl., 412 (2014), 181–188
work page 2014
- [40]
-
[41]
O. Ladyzenskaja, V. Solonnikov, N. Uralceva, Linear and quasi-linear equations of parabolic type, American Mathematical Society, 1968
work page 1968
-
[42]
H. Amann, Linear and Quasilinear Parabolic Problems: Volume I, Abstract Linear Theory, Birkh¨ auser Verlag, Basel, (1995)
work page 1995
-
[43]
Y. Tao, M. Winkler, Boundedness in a quasilinear parabolic-parabolic Keller-Segel system with subcritical sensitivity, J. Differ. Equ., 252 (2012), 692-715
work page 2012
-
[44]
X. Bai, M. Winkler, Equilibration in a fully parabolic two-species chemotaxis system with competitive ki- netics, Indiana Univ. Math. J., 65 (2016), 553-583
work page 2016
-
[45]
M. Wang, A diffusive logistic equation with a free boundary and sign-changing coefficient in time-periodic environment, J. Funct. Anal., 270 (2016), 483–508
work page 2016
-
[46]
J. Wang, M. Wang, The diffusive Beddington–DeAngelis predator–prey model with nonlinear prey-taxis and free boundary, Math. Methods Appl. Sci., 41 (2018), 6741–6762
work page 2018
-
[47]
T. Li, A. Suen, M. Winkler, C. Xue, Global small-data solutions of a two-dimensional chemotaxis system with rotational flux terms, Math. Models Methods Appl. Sci., 25 (2015), 721–746
work page 2015
-
[48]
M.M. Porzio, V. Vespri, Holder estimates for local solutions of some doubly nonlinear degenerate parabolic equations, J. Differ. Equ., 103 (1993), 146–178. (GS)Department of Mathematics, National Institute of Technology Tiruchirappalli, Tamil- nadu 620015, India Email address:sekaran@nitt.edu (JS)Department of Mathematics, National Institute of Technology...
work page 1993
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.