Mixotrophs combine resource use to outcompete specialists: Implications for aquatic food webs
Mixotrophs combine resource use to outcompete specialists: Implications for aquatic food webs
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DOI：
10.1073/pnas.2130696100
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发表时间：
2003-10-28
影响因子：
11.1
通讯作者：
Kamjunke, N
中科院分区：
文献类型：
--
作者：
Tittel, J;Bissinger, V;Kamjunke, N
大多数生物可以分为那些只依靠光合作用（光养）或那些只依靠有机物质的同化（异养），以满足其对能量和碳的需求。然而，存在一种特殊的生活史特征，其中生物联合收割机结合了光养和异养。这种“混合营养”是水生生境中的一种普遍现象，在许多原生动物和后生动物生物体中观察到。该策略需要在光合和异养细胞装置上进行投资，并且收益必须超过这些成本。根据机械资源竞争理论，实验室实验表明，色素混合营养体结合光，矿物质营养物质和猎物作为替代资源。因此，他们减少了猎物丰度低于竞争专业食草动物的临界食物浓度[Rothhaupt，K。O.（1996）Ecology 77，716-724）。在这里，我们展示了这一战略的水生社区的重要后果。在照明表层的湖泊混合营养体减少猎物丰度急剧。这些数据表明，作为一个结果，食草动物从更高的营养水平，消费的mixotrophs和他们的猎物，不能坚持。因此，混合营养体逃脱了与更高的食草动物的竞争和损失。此外，mixotrophs结构的猎物丰富沿着垂直光梯度，创造低密度附近的表面和一个显着的最大值，他们的藻类猎物在深度。这种深层藻类积累是营养贫乏的水生生境的典型特征，以前用资源可用性来解释。我们假设，而不是混合营养放牧策略是负责在许多水生环境中的深层藻类积累。
The majority of organisms can be grouped into those relying solely on photosynthesis (phototrophy) or those relying solely on the assimilation of organic substances (heterotrophy) to meet their requirements for energy and carbon. However, a special life history trait exists in which organisms combine both phototrophy and heterotrophy. Such "mixotrophy" is a widespread phenomenon in aquatic habitats and is observed in many protozoan and metazoan organisms. The strategy requires investment in both photosynthetic and heterotrophic cellular apparatus, and the benefits must outweigh these costs. In accordance with mechanistic resource competition theory, laboratory experiments revealed that pigmented mixotrophs combined light, mineral nutrients, and prey as substitutable resources. Thereby, they reduced prey abundance below the critical food concentration of competing specialist grazers [Rothhaupt, K. O. (1996) Ecology 77, 716-724). Here, we demonstrate the important consequences of this strategy for an aquatic community. In the illuminated surface strata of a lake mixotrophs reduced prey abundance steeply. The data suggest that, as a consequence, grazers from higher trophic levels, consuming both the mixotrophs and their prey, could not persist. Thus, the mixotrophs escaped from competition with and losses to higher grazers. Furthermore, the mixotrophs structured prey abundance along the vertical light gradient, creating low densities near the surface and a pronounced maximum of their algal prey at depth. Such deep algal accumulations are typical features of nutrient-poor aquatic habitats, previously explained by resource availability. We hypothesize instead that the mixotrophic grazing strategy is responsible for deep algal accumulations in many aquatic environments.