When does local spatial structure hinder competitive coexistence and reverse competitive hierarchies?
When does local spatial structure hinder competitive coexistence and reverse competitive hierarchies?
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DOI：
10.1890/09-0832.1
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发表时间：
2010-06-01
期刊：
影响因子：
4.8
通讯作者：
Murrell, David J.
中科院分区：
文献类型：
--
作者：
Murrell, David J.
经典理论认为，如果同种对个体的竞争效应大于异种，那么共存就应该发生，生态学家花费了大量精力探索在不满足这种条件时产生共存的方法。过去二十年受到特别关注的一个过程是有限扩散引起的物种内聚集和物种间隔离的影响。关于这种共同的空间模式如何帮助维持生物多样性，已经出现了许多理论，并且已经出现的普遍结论是，空间结构几乎总是应该有助于竞争者共存。但空间结构真的总是有助于生物多样性吗？提出了一种基于 Lotka-Volterra 竞争方程的空间扩展及其数学近似的基于个体的模型，以确定局部空间结构如何影响存在强烈生态位分化的群落。模型分析得出两个主要结果。首先，当空间结构较强时，种内竞争大于种间竞争共存可能不再足以产生共存；种内竞争系数最高的物种很可能被排除。其次，当在短空间尺度上发生分散和竞争相互作用时，优势等级可能会发生逆转，使得竞争者可能成为从属物种。这两个结果的出现是因为，尽管一个物种可能在全球范围内罕见，但强烈的聚集意味着大多数相互作用发生在同种之间，如果这种相互作用非常强烈，则可能足以阻止一个物种的入侵。然而，长距离扩散可以通过减少同种相互作用的频率来改善这些影响，当一个物种很稀有时，这一点尤其重要，因为它很可能降落在异种占主导地位的地区。这些结果与固着生物最相关，这些固着生物产生相对较少的存活到成年的可存活后代并且传播相对较弱。结论是，当个体可能面临的最强劲的竞争对手是其自身物种的成员时，物种内聚集可能会阻碍共存。
Classical theory states that if conspecifics have a greater competitive effect on individuals than heterospecifics then coexistence should occur, and ecologists have spent much effort exploring ways to generate coexistence when this condition is not met. One process that has received particular attention in the last two decades is the effect of within-species aggregation and between-species segregation caused by limited dispersal. A number of theories have emerged as to how this common spatial pattern may help maintain biodiversity, and the general conclusion that has emerged is that spatial structure should almost always help competitors to coexist. But does spatial structure really always aid biodiversity? An individual-based model based on a spatial extension to the Lotka-Volterra competition equations and its mathematical approximation are presented to determine how local spatial structure may affect communities in which there is strong niche differentiation. Two main results emerge from analyses of the models. First, intraspecific competition being greater than interspecific competition coexistence may no longer be sufficient to generate coexistence when spatial structure is strong; and the species with the highest intraspecific competition coefficient is likely to be excluded. Second, dominance hierarchies may be reversed so that a competitor may become the subordinate species when dispersal and competitive interactions occur over short spatial scales. Both results emerge because, even though a species may be globally rare, intense clumping means most interactions occur between conspecifics, and if this is very intense it may be sufficient to stop a species from invading. However, long-range dispersal may ameliorate these effects by reducing the frequency of conspecific interactions, and this is especially important when a species is rare since it is very likely to land in an area dominated by heterospecifics. These results are most relevant to sessile organisms that produce relatively few viable offspring that survive to adulthood and that have relatively weak dispersal. The conclusion is that within-species aggregation may hinder coexistence when the toughest competitor an individual is likely to face is a member of its own species.