McCoy Rachel M, Widhalm Joshua R, McNickle Gordon G
Purdue Center for Plant Biology Purdue University West Lafayette IN USA.
Department of Horticulture and Landscape Architecture Purdue University West Lafayette IN USA.
Plant Direct. 2022 Feb 11;6(2):e382. doi: 10.1002/pld3.382. eCollection 2022 Feb.
In plants, most competition is resource competition, where one plant simply preempts the resources away from its neighbors. Interference competition, as the name implies, is a form of direct interference to prevent resource access. Interference competition is common among animals that can physically fight, but in plants, one of the main mechanisms of interference competition is allelopathy. Allelopathic plants release cytotoxic chemicals into the environment which can increase their ability to compete with surrounding organisms for limited resources. The circumstances and conditions favoring the development and maintenance of allelochemicals, however, are not well understood. Particularly, despite the obvious benefits of allelopathy, current data suggest it seems to have only rarely evolved. To gain insight into the cost and benefit of allelopathy, we have developed a matrix game to model the interaction between plants that produce allelochemicals and plants that do not. Production of an allelochemical introduces novel cost associated with both synthesis and detoxifying a toxic chemical but may also convey a competitive advantage. A plant that does not produce an allelochemical will suffer the cost of encountering one. Our model predicts three cases in which the evolutionarily stable strategies are different. In the first, the nonallelopathic plant is a stronger competitor, and not producing allelochemicals is the evolutionarily stable strategy. In the second, the allelopathic plant is the better competitor, and production of allelochemicals is the more beneficial strategy. In the last case, neither is the evolutionarily stable strategy. Instead, there are alternating stable states, depending on whether the allelopathic or nonallelopathic plant arrived first. The generated model reveals circumstances leading to the evolution of allelochemicals and sheds light on utilizing allelochemicals as part of weed management strategies. In particular, the wide region of alternative stable states in most parameterizations, combined with the fact that the absence of allelopathy is likely the ancestral state, provides an elegant answer to the question of why allelopathy seems to rarely evolve despite its obvious benefits. Allelopathic plants can indeed outcompete nonallelopathic plants, but this benefit is simply not great enough to allow them to go to fixation and spread through the population. Thus, most populations would remain purely nonallelopathic.
在植物中，大多数竞争是资源竞争，即一种植物只是从其邻居那里抢占资源。顾名思义，干扰竞争是一种直接干扰形式，旨在阻止获取资源。干扰竞争在能够进行物理争斗的动物中很常见，但在植物中，干扰竞争的主要机制之一是化感作用。化感植物会向环境中释放细胞毒性化学物质，这可以增强它们与周围生物争夺有限资源的能力。然而，有利于化感物质发展和维持的环境和条件尚未得到充分了解。特别是，尽管化感作用有明显益处，但目前的数据表明它似乎很少进化。为了深入了解化感作用的成本和收益，我们开发了一个矩阵博弈模型，以模拟产生化感物质的植物与不产生化感物质的植物之间的相互作用。产生化感物质会带来与合成和解毒有毒化学物质相关的新成本，但也可能带来竞争优势。不产生化感物质的植物会遭受遇到化感物质的成本。我们的模型预测了三种进化稳定策略不同的情况。第一种情况是，非化感植物是更强的竞争者，不产生化感物质是进化稳定策略。第二种情况是，化感植物是更好的竞争者，产生化感物质是更有利的策略。在最后一种情况下，两者都不是进化稳定策略。相反，存在交替稳定状态，这取决于化感植物还是非化感植物先出现。生成的模型揭示了导致化感物质进化的情况，并为将化感物质用作杂草管理策略的一部分提供了启示。特别是，大多数参数设置中的广泛交替稳定状态区域，再加上化感作用不存在可能是原始状态这一事实，为为什么化感作用尽管有明显益处却似乎很少进化这一问题提供了一个巧妙的答案。化感植物确实可以胜过非化感植物，但这种益处还不足以使其固定下来并在种群中传播。因此，大多数种群将保持纯粹的非化感状态。
