Parasite-mediated and direct competition in a two-host shared macroparasite system
Parasite-mediated and direct competition in a two-host shared macroparasite system
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DOI：
10.1006/tpbi.1999.1435
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发表时间：
2000-02-01
影响因子：
1.4
通讯作者：
Hudson, PJ
中科院分区：
文献类型：
--
作者：
Greenman, JV;Hudson, PJ
本文研究了一个确定性模型的局部动态行为，该模型描述了两个寄主物种经历三种形式的竞争：直接竞争、由大型寄生虫介导的表观竞争和种内（密度依赖）竞争。采用几何方法回避了代数难解性的问题，其中在参数空间中构造了一系列映射，每个映射由分岔曲面构成，分岔曲面标志着系统行为的质变。这些图提供了系统平衡的稳定性和可行性结构的简洁和全面的概述，从中可以推导出局部动力学行为的可能模式。对这些图的详细检查表明：(1)系统对感染对繁殖力的影响高度敏感，Hopf分岔容易产生同步持续周期；（ii）对于与实际生物系统相关的广泛参数值，由大型寄生虫介导的明显竞争本身就足以解释宿主排斥；（iii）直接竞争加强了寄生虫介导的竞争，扩大了宿主排斥区域；（iv）宿主排斥的条件可以简单地用一种既适用于微型寄生虫模型也适用于大型寄生虫模型的形式来表达，这种形式只涉及两个关键指标，即测量对感染的耐受性和直接竞争的强度。本文中使用的技术不仅限于宿主-寄生虫系统的分析，而且可以应用于广泛的非线性种群模型。因此，它们既与具体的流行病学问题有关，也与分析剥削性竞争和营养相互作用等一般问题有关。(C) 2000年学术出版社。
This paper investigates the local dynamical behaviour of a deterministic model describing two host species experiencing three forms of competition: direct competition, apparent competition mediated by macroparasites, and intra-specific (density-dependent) competition. The problem of algebraic intractability is sidestepped by adopting a geometric approach, in which an array of maps is constructed in parameter space, each structured by bifurcation surfaces which mark qualitative changes in system behaviour. The maps provide both a succinct and a comprehensive overview of the stability and feasibility structure of the system equilibria, from which can be deduced the possible modes of local dynamical behaviour. A detailed examination of these maps shows that (i) the system is highly sensitive to the effect of infection on fecundity with synchronous sustained cycles readily generated by Hopf bifurcations; (ii)for a broad range of parameter values, pertinent to actual biological systems, apparent competition mediated by macroparasites is sufficient, on its own, to explain host exclusion; (iii) direct competition reinforces parasite-mediated competition to expand the host exclusion region; and (iv)the condition for host exclusion can be expressed simply in a form which holds for both micro- and macroparasite models and which involves just two key indices, measuring tolerance to the infection and the strength of direct competition. The techniques used in this paper are not restricted to the analysis of host-parasite systems but can be applied to a wide range of nonlinear population models. They are therefore as relevant to the analysis of such general issues as exploitative competition and trophic interactions as they are to specific epidemiological problems. (C) 2000 Academic Press.