Evolution of resource use along a gradient of stress leads to increased facilitation
Evolution of resource use along a gradient of stress leads to increased facilitation
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DOI：
10.1111/oik.02989
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发表时间：
2016-09-01
期刊：
影响因子：
3.4
通讯作者：
Barraclough, Timothy G.
中科院分区：
文献类型：
--
作者：
Lawrence, Diane;Barraclough, Timothy G.
胁迫梯度假说（SGH）认为，随着非生物胁迫水平的升高，促进性相互作用相对于负面相互作用的相对重要性增加。该假说最初是在植物种群的实证研究中提出的，近年来人们发现它可以描述包括藻类、贻贝和蛾类在内的众多物种的相互作用如何随着胁迫而改变。然而，很少有理论试图从基本原理出发预测与不同类型相互作用相关的模式。在此，我们利用微生物种群的数学模型来研究当物种通过资源利用和化感作用相互作用时，是否会出现与SGH一致的模式。进化改变了资源利用竞争与促进作用（交叉喂养）发生的程度。我们的结果与SGH一致；随着平均胁迫加剧，物种间的相互作用逐渐变得更具促进性。这是因为在更大的胁迫下，物种进化为两种资源中某一种的专性物种，从而减少了资源利用的重叠，并通过交叉喂养增加了促进作用。此外，由于密度依赖效应，随着胁迫加剧，有毒化感化合物的产生会减少。我们的结果表明，SGH可能通过许多生物共有的基本相互作用而产生，因此SGH可能是一种比之前所认识的更为普遍的现象。
The stress-gradient hypothesis (SGH) posits that the relative importance of facilitative interactions versus negative interactions increases as levels of abiotic stress increase. Originally formulated in empirical studies of plant populations, in recent years the SGH has been found to describe how interactions change in response to stress in a wide range of species including algae, mussels and moths. However, there has been little theory attempting to predict patterns from first principles in relation to different types of interactions. Here, we use mathematical models of microbial populations to investigate whether patterns consistent with the SGH arise when species interact through resource use and allelopathy. Evolution alters the degree to which competition for resource use versus facilitation (cross-feeding) occurs. Our results are consistent with the SGH; species interactions evolve to be more facilitative as average stress intensifies. This occurs because at greater stress the species evolve to become specialists on either of the two resources thereby decreasing overlap in resource use and increasing facilitation through cross-feeding. In addition, the production of toxic allelopathic compounds decreases as stress intensifies due to density-dependent effects. Our results suggest that the SGH could arise through fundamental interactions that are common to many organisms and therefore that the SGH could be a more widespread phenomenon than previously recognised.