The evolution and maintenance of omnivory: Dynamic constraints and the role of food quality
The evolution and maintenance of omnivory: Dynamic constraints and the role of food quality
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DOI：
10.1890/02-0399
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发表时间：
2003-10-01
期刊：
影响因子：
4.8
通讯作者：
Diehl, S
中科院分区：
文献类型：
--
作者：
Diehl, S
在一些分类群中，从多个营养级进行杂食性捕食的能力是从更专门的捕食习惯进化而来的。这种进化情景的先决条件是消费者随后参与杂食性的最初共存（在相同或不同的营养水平上）。消费者互动中先前的不对称也应该有利于杂食的进化。我使用动态模型来简单地探索依赖于单一生物资源的两个消费者共存的条件。消费者之间的食物网日益不对称：（1）纯粹的资源竞争，（2）单向干扰的资源竞争，（3）杂食性，（4）纯粹的捕食。如果消费者的能量有限，杂食性就不太可能从竞争系统中演化出来，因为即使在资源开发和干扰能力之间存在权衡，两个消费者在单一资源上稳定共存也是不可能的。如果物种排列在食物链中，则两个消费者的初始共存更容易实现。如果饮食泛化的成本较低，那么选择应该倾向于将资源纳入顶级消费者的饮食中。然而，在具有高资源承载能力的系统中，中间消费者将经常被推向灭绝——在这种情况下，杂食性就无法维持。资源的低营养质量可以稳定杂食系统，并允许三个物种在高资源承载能力下共存。资源的低营养质量也可能为杂食性从竞争性系统的进化创造条件。如果资源生物量中必需养分的含量是动态的，并且两个竞争者都受到资源养分含量的限制，那么两个竞争者的稳定共存就成为可能。在这种情况下，选择可能有利于杂食性的进化，因为竞争者生物量通常比资源生物量具有更高的营养质量。因此，对灵活资源化学计量的明确处理拓宽了杂食动物进化的可能性。
In several taxa, the ability to feed omnivorously from more than one trophic level has evolved from more specialized feeding habits. A prerequisite for this evolutionary scenario is initial coexistence (on the same or different trophic levels) of the consumers subsequently involved in omnivory. Evolution of omnivory should also be favored by prior asymmetries in consumer interactions. I use a dynamic model to explore conditions for coexistence of two consumers depending on a single biotic resource in simple. food webs of increasing asymmetry between consumers: (1) pure resource competition, (2) resource competition with unidirectional interference, (3) omnivory, and (4) pure predation. If consumers are energy limited, omnivory is unlikely to evolve from a competitive system, because stable coexistence of two consumers on a single resource is impossible, even if there is a trade-off between resource exploitation and interference abilities. Initial coexistence of two consumers is easier to achieve, if the species are arranged in a food chain. If costs of diet generalization are low, selection should then favor the inclusion of the resource in the top consumer's diet. In systems with high resource carrying capacity, the intermediate consumer will then, however, be frequently driven to extinction-in which case omnivory is not maintained. Low nutritional quality of the resource can stabilize the omnivory system and allow three-species coexistence at high resource carrying capacities. Low nutritional quality of the resource may also create conditions for the evolution of omnivory from a competitive system. If the content of an essential nutrient in resource biomass is dynamic, stable coexistence of two competitors becomes possible if both are limited by the nutrient content of the resource. In this case, selection may favor the, evolution of omnivory, because competitor biomass is usually of higher nutritional quality than resource biomass. An explicit treatment of flexible resource stoichiometry thus broadens the possibilities for the evolution of omnivory.