Adaptive Dynamics of Competition for Nutritionally Complementary Resources: Character Convergence, Displacement, and Parallelism
Adaptive Dynamics of Competition for Nutritionally Complementary Resources: Character Convergence, Displacement, and Parallelism
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营养互补资源竞争的自适应动态：特征趋同、置换和平行
作者：
David A. Vasseur;J. Fox
消费者通过摄取资源物种的组织来获得必要的营养。当这些组织含有低于最佳比例的基本营养素时，消费者可能会从摄入营养互补的资源物种的混合物中受益。我们使用两个消费者和两种资源的适应性动力学模型研究了竞争互补资源的联合生态和进化后果，两种资源的两种基本营养物质的相对含量不同。在没有竞争的情况下，营养平衡的饮食很少能使健康最大化，因为摄取率和资源密度之间存在动态反馈；而在共同的情况下，营养平衡的饮食使健康最大化，因为具有不同营养需求的竞争消费者往往会使这两种资源的相对丰度相等。从异地适应到共域适应最优可以产生性格的收敛、分化和平行转变，这不取决于饮食重叠的程度，而是取决于资源营养含量和消费者营养需求之间的匹配。与之前口头上认为性格趋同会导致中性稳定的观点相反，竞争性消费者的共同适应总是会导致稳定的共存。此外，我们还表明，将摄入或排泄过量的非限制性营养素的成本纳入选择营养均衡的饮食，从而促进性格的趋同。本文论证了当资源在营养上互补时，资源利用重叠对共存的影响不大，并强调了使用数学模型来推断生态进化动力学稳定性的重要性。
Consumers acquire essential nutrients by ingesting the tissues of resource species. When these tissues contain essential nutrients in a suboptimal ratio, consumers may benefit from ingesting a mixture of nutritionally complementary resource species. We investigate the joint ecological and evolutionary consequences of competition for complementary resources, using an adaptive dynamics model of two consumers and two resources that differ in their relative content of two essential nutrients. In the absence of competition, a nutritionally balanced diet rarely maximizes fitness because of the dynamic feedbacks between uptake rate and resource density, whereas in sympatry, nutritionally balanced diets maximize fitness because competing consumers with different nutritional requirements tend to equalize the relative abundances of the two resources. Adaptation from allopatric to sympatric fitness optima can generate character convergence, divergence, and parallel shifts, depending not on the degree of diet overlap but on the match between resource nutrient content and consumer nutrient requirements. Contrary to previous verbal arguments that suggest that character convergence leads to neutral stability, coadaptation of competing consumers always leads to stable coexistence. Furthermore, we show that incorporating costs of consuming or excreting excess nonlimiting nutrients selects for nutritionally balanced diets and so promotes character convergence. This article demonstrates that resource-use overlap has little bearing on coexistence when resources are nutritionally complementary, and it highlights the importance of using mathematical models to infer the stability of ecoevolutionary dynamics.