TY - JOUR

T1 - Timescales of population rarity and commonness in random environments

AU - Ferriere, Regis

AU - Guionnet, Alice

AU - Kurkova, Irina

N1 - Funding Information:
We are grateful to O. Zeitouni for pointing out some useful references, and to an anonymous reviewer for helping us clarify the presentation of our results. R.F. received financial support from the French Ministries of Research and Environment (ACI Programme ‘Invasions Biologiques’ and ACI Programme ‘Nouvelles Interfaces des Mathématiques’).

PY - 2006/6

Y1 - 2006/6

N2 - This is a mathematical study of the interactions between non-linear feedback (density dependence) and uncorrelated random noise in the dynamics of unstructured populations. The stochastic non-linear dynamics are generally complex, even when the deterministic skeleton possesses a stable equilibrium. There are three critical factors of the stochastic non-linear dynamics; whether the intrinsic population growth rate ( λ ) is smaller than, equal to, or greater than 1; the pattern of density dependence at very low and very high densities; and whether the noise distribution has exponential moments or not. If λ < 1, the population process is generally transient with escape towards extinction. When λ {greater than or slanted equal to} 1, our quantitative analysis of stochastic non-linear dynamics focuses on characterizing the time spent by the population at very low density (rarity), or at high abundance (commonness), or in extreme states (rarity or commonness). When λ > 1 and density dependence is strong at high density, the population process is recurrent: any range of density is reached (almost surely) in finite time. The law of time to escape from extremes has a heavy, polynomial tail that we compute precisely, which contrasts with the thin tail of the laws of rarity and commonness. Thus, even when λ is close to one, the population will persistently experience wide fluctuations between states of rarity and commonness. When λ = 1 and density dependence is weak at low density, rarity follows a universal power law with exponent - frac(3, 2). We provide some mathematical support for the numerical conjecture [Ferriere, R., Cazelles, B., 1999. Universal power laws govern intermittent rarity in communities of interacting species. Ecology 80, 1505-1521.] that the - frac(3, 2) power law generally approximates the law of rarity of 'weakly invading' species with λ values close to one. Some preliminary results for the dynamics of multispecific systems are presented.

AB - This is a mathematical study of the interactions between non-linear feedback (density dependence) and uncorrelated random noise in the dynamics of unstructured populations. The stochastic non-linear dynamics are generally complex, even when the deterministic skeleton possesses a stable equilibrium. There are three critical factors of the stochastic non-linear dynamics; whether the intrinsic population growth rate ( λ ) is smaller than, equal to, or greater than 1; the pattern of density dependence at very low and very high densities; and whether the noise distribution has exponential moments or not. If λ < 1, the population process is generally transient with escape towards extinction. When λ {greater than or slanted equal to} 1, our quantitative analysis of stochastic non-linear dynamics focuses on characterizing the time spent by the population at very low density (rarity), or at high abundance (commonness), or in extreme states (rarity or commonness). When λ > 1 and density dependence is strong at high density, the population process is recurrent: any range of density is reached (almost surely) in finite time. The law of time to escape from extremes has a heavy, polynomial tail that we compute precisely, which contrasts with the thin tail of the laws of rarity and commonness. Thus, even when λ is close to one, the population will persistently experience wide fluctuations between states of rarity and commonness. When λ = 1 and density dependence is weak at low density, rarity follows a universal power law with exponent - frac(3, 2). We provide some mathematical support for the numerical conjecture [Ferriere, R., Cazelles, B., 1999. Universal power laws govern intermittent rarity in communities of interacting species. Ecology 80, 1505-1521.] that the - frac(3, 2) power law generally approximates the law of rarity of 'weakly invading' species with λ values close to one. Some preliminary results for the dynamics of multispecific systems are presented.

KW - Ecological timescales

KW - Environmental stochasticity

KW - Markov chains

KW - Martingales

KW - On-off intermittency

KW - Population dynamics

KW - Power law

KW - Rarity

KW - Stochastic non-linear difference equations

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U2 - 10.1016/j.tpb.2006.01.005

DO - 10.1016/j.tpb.2006.01.005

M3 - Article

C2 - 16527320

AN - SCOPUS:33646125613

SN - 0040-5809

VL - 69

SP - 351

EP - 366

JO - Theoretical Population Biology

JF - Theoretical Population Biology

IS - 4

ER -