Department of Biological Sciences, Simon Fraser University 8888 University Drive, Burnaby, British Columbia, V5A1S6, Canada.
ESSA Technologies Ltd. Vancouver, British Columbia, V6H 3H4, Canada.
Ecol Evol. 2014 Feb;4(3):251-65. doi: 10.1002/ece3.923. Epub 2013 Dec 29.
Omnivory is extremely common in animals, yet theory predicts that when given a choice of resources specialization should be favored over being generalist. The evolution of a feeding phenotype involves complex interactions with many factors other than resource choice alone, including environmental heterogeneity, resource quality, availability, and interactions with other organisms. We applied an evolutionary simulation model to examine how ecological conditions shape evolution of feeding phenotypes (e.g., omnivory), by varying the quality and availability (absolute and relative) of plant and animal (prey) resources. Resulting feeding phenotypes were defined by the relative contribution of plants and prey to diets of individuals. We characterized organisms using seven traits that were allowed to evolve freely in different simulated environments, and we asked which traits are important for different feeding phenotypes to evolve among interacting organisms. Carnivores, herbivores, and omnivores all coexisted without any requirement in the model for a synergistic effect of eating plant and animal prey. Omnivores were most prevalent when ratio of plants and animal prey was low, and to a lesser degree, when habitat productivity was high. A key result of the model is that omnivores evolved through many different combinations of trait values and environmental contexts. Specific combinations of traits tended to form emergent trait complexes, and under certain environmental conditions, are expressed as omnivorous feeding phenotypes. The results indicate that relative availabilities of plants and prey (over the quality of resources) determine an individual's feeding class and that feeding phenotypes are often the product of convergent evolution of emergent trait complexes under specific environmental conditions. Foraging outcomes appear to be consequences of degree and type of phenotypic specialization for plant and animal prey, navigation and exploitation of the habitat, reproduction, and interactions with other individuals in a heterogeneous environment. Omnivory should not be treated as a fixed strategy, but instead a pattern of phenotypic expression, emerging from diverse genetic sources and coevolving across a range of ecological contexts.
杂食性在动物中极为常见，但理论预测，在有资源选择的情况下，专业化应该优于泛化。摄食表型的进化涉及与资源选择以外的许多因素的复杂相互作用，包括环境异质性、资源质量、可用性以及与其他生物体的相互作用。我们应用进化模拟模型，通过改变植物和动物（猎物）资源的质量和可用性（绝对和相对），来研究生态条件如何塑造摄食表型（例如杂食性）的进化。所得摄食表型由个体饮食中植物和猎物的相对贡献来定义。我们使用七个允许在不同模拟环境中自由进化的特征来描述生物体，并询问在相互作用的生物体中，哪些特征对于不同的摄食表型的进化是重要的。在模型中，不需要食用植物和动物猎物的协同效应，就可以使肉食动物、草食动物和杂食动物共存。当植物和动物猎物的比例较低时，杂食动物最为普遍，在一定程度上，当栖息地生产力较高时也是如此。该模型的一个关键结果是，杂食动物通过许多不同的特征值组合和环境背景进化而来。特征的特定组合往往形成新兴的特征综合体，并且在某些环境条件下，表现为杂食性摄食表型。结果表明，植物和猎物的相对可利用性（相对于资源质量）决定了个体的摄食类群，并且摄食表型通常是特定环境条件下新兴特征综合体趋同进化的产物。觅食结果似乎是对植物和动物猎物的表型专业化程度和类型的结果，以及在异质环境中对栖息地的导航和利用、繁殖以及与其他个体的相互作用。杂食性不应被视为一种固定策略，而应是一种表型表达模式，它源自多种遗传来源，并在一系列生态环境中共同进化。
