[论文解读] On the sympatric evolution of coexistence by relative nonlinearity of competition

Florian Härtig, Tamara Münkemülle+2 more|arXiv (Cornell University)|Aug 14, 2013

Plant and animal studies参考文献 55被引用 1

一句话总结

本研究利用适应性动力学与个体为基础的模拟，探讨了通过竞争的相对非线性实现共存的机制是否可能在同域条件下演化。研究发现，尽管在广泛的参数范围内共存具有动态稳定性，但只有极特定的进化权衡才能实现长期的进化稳定性——这意味着尽管该机制在理论上可行，但在自然界中同域演化该机制的可能性较低。

ABSTRACT

If two species show dierent nonlinear responses to a single shared resource, and if each species modifies resource dynamics such that it favors its competitor, they may stably coexist. While the mechanism behind this phenomenon, known as relative nonlinearity of competition, is well understood, less is known about its evolutionary properties and its prevalence in real communities. We address this challenge by using the adaptive dynamics framework as well as individual-based simulations to compare dynamic and evolutionary stability of communities coexisting through relative nonlinearity. Evolution operates on the species’ density compensation strategies, and a trade-o between growth at high versus low resource availability (population density) is assumed. We confirm previous findings that, irrespective of the particular model of density-dependence, there are usually broad ranges of coexistence between overcompensating and undercompensating density-compensation strategies. We show that most of these strategies, however, are not evolutionarily stable and will be outcompeted by a single compensatory strategy. Only very specific evolutionary tradeos allow evolutionary stability of strategies that coexist through relative nonlinearity. As we find no reason why these particular trade-os should be abundant in nature, we conclude that sympatric evolution of relative nonlinearity seems possible, but rather unlikely. We speculate that this may explain why relative nonlinearity has seldom been observed, although we note that a low probability of sympatric evolution does not exclude the possibility that this mechanism of coexistence might still frequently occur when species with dierent evolutionary histories meet in the same community. Our results highlight the need for combining ecological and evolutionary perspectives for understanding community assembly and biogeographical patterns.

研究动机与目标

• 评估基于竞争相对非线性的共存机制的进化稳定性。
• 确定物种是否能演化出通过差异化非线性响应共享资源而实现稳定共存的策略。
• 利用进化与生态建模，评估此类共存机制在自然群落中的普遍性与可行性。

提出的方法

• 采用适应性动力学框架，模拟物种在密度补偿策略上的进化分支与趋同。
• 通过个体为基础的模拟，追踪在不同生态与进化条件下种群动态与进化轨迹。
• 将密度补偿策略建模为在高资源与低资源可用性（密度）下表现的权衡。
• 模型中纳入对资源可用性的过度补偿与不足补偿响应，以模拟非线性竞争。
• 通过分析生态与进化动态下共存平衡点的稳定性，评估共存状态。
• 比较动态稳定性（无进化背景下的共存）与进化稳定性（对突变策略入侵的抵抗能力）

实验结果

研究问题

• RQ1 在现实的进化权衡下，通过竞争相对非线性实现共存是否可能在同域条件下演化？
• RQ2 在高密度与低密度下表现之间的哪些特定权衡可实现共存策略的进化稳定性？
• RQ3 在自然系统中，实现进化稳定性的必要条件有多普遍？
• RQ4 共存的动态稳定性在多大程度上意味着进化稳定性？
• RQ5 尽管该机制在理论上可行，为何在自然界中却很少被观察到？

主要发现

• 无论具体的密度依赖模型如何，通过竞争相对非线性实现的动态共存对广泛的密度补偿策略均保持稳定。
• 大多数共存策略在进化上不稳定，会在选择压力下被单一高度补偿性的策略所取代。
• 只有在物种以精确方式平衡高、低资源水平下的表现时，才可能实现共存策略的进化稳定性。
• 实现进化稳定性的所需权衡极为狭窄且特定，因此在自然界中不太可能普遍存在。
• 相对非线性同域演化的低概率或可解释其在经验观察中罕见的现象，即使当具有不同进化历史的物种共存时，该机制仍可能有效运作。
• 研究结果强调了整合生态学与进化视角对于理解群落构建与生物地理格局的重要性。