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arXiv 0712.2654q-bio.PEcond-mat.stat-mechphysics.bio-ph
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一个食物网〈动〉<动>模型的灭绝风险与结构

Extinction risk and structure of a food web model

A. Pȩkalski, J. Szwabiński, I. Bena, M. Droz

摘要:

我们详细研究了由Amaral和Meyer提出的营养网模型[Phys. Rev. Lett. 82,652(1999)]。我们关注的是与真实生物食物网相关的小规模系统,波动在其中发挥着重要作用。我们表明,使用Monte Carlo模拟,这样的网络可以是不可行的,导致所有物种在小和/或弱耦合系统的灭绝。并给出了灭绝时间和生存机会的估计。我们发现,在灭绝之前,高度连接的物种(“杂食动物”)的比例正在增加。有活力的食物网呈现金字塔结构,在较低的营养级,被占据的生态位密度较高,而且相邻层次的职业密切相关。我们还证明了食物链〈动〉<动>的长度分布具有指数特征,并且随模型参数的变化很弱。相反,灭绝物种的雪崩大小的分布强烈依赖于网络的连通性。对于松散连接的系统,我们恢复幂律类型的行为与在早期的研究中发现的相同的指数,而密集连接的网络的分布是不是幂律类型。

英文摘要:

We investigate in detail the model of a trophic web proposed by Amaral and Meyer [Phys. Rev. Lett. 82, 652 (1999)]. We focused on small-size systems that are relevant for real biological food webs and for which the fluctuations are playing an important role. We show, using Monte Carlo simulations, that such webs can be non-viable, leading to extinction of all species in small and/or weakly coupled systems. Estimations of the extinction times and survival chances are also given. We show that before the extinction the fraction of highly-connected species ("omnivores") is increasing. Viable food webs exhibit a pyramidal structure, where the density of occupied niches is higher at lower trophic levels, and moreover the occupations of adjacent levels are closely correlated. We also demonstrate that the distribution of the lengths of food chains has an exponential character and changes weakly with the parameters of the model. On the contrary, the distribution of avalanche sizes of the extinct species depends strongly on the connectedness of the web. For rather loosely connected systems we recover the power-law type of behavior with the same exponent as found in earlier studies, while for densely-connected webs the distribution is not of a power-law type.

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