Centre for Ocean Life, DTU Aqua, Technical University of Denmark, DK-2800 Kgs Lyngby, Denmark;
Centre for Ocean Life, DTU Aqua, Technical University of Denmark, DK-2800 Kgs Lyngby, Denmark.
Proc Natl Acad Sci U S A. 2020 Oct 6;117(40):24893-24899. doi: 10.1073/pnas.2008370117. Epub 2020 Sep 23.
Gleaners and exploiters (opportunists) are organisms adapted to feeding in nutritionally poor and rich environments, respectively. A trade-off between these two strategies-a negative relationship between the rate at which organisms can acquire food and ingest it-is a critical assumption in many ecological models. Here, we evaluate evidence for this trade-off across a wide range of heterotrophic eukaryotes from unicellular nanoflagellates to large mammals belonging to both aquatic and terrestrial realms. Using data on the resource acquisition and ingestion rates in >500 species, we find no evidence of a trade-off across species. Instead, there is a positive relationship between maximum clearance rate and maximum ingestion rate. The positive relationship is not a result of lumping together diverse taxa; it holds within all subgroups of organisms we examined as well. Correcting for differences in body mass weakens but does not reverse the positive relationship, so this is not an artifact of size scaling either. Instead, this positive relationship represents a slow-fast gradient in the "pace of life" that overrides the expected gleaner-exploiter trade-off. Other trade-offs must therefore shape ecological processes, and investigating them may provide deeper insights into coexistence, competitive dynamics, and biodiversity patterns in nature. A plausible target for study is the well-documented trade-off between growth rate and predation avoidance, which can also drive the slow-fast gradient we observe here.
拾荒者和剥削者（机会主义者）分别是适应在营养贫瘠和丰富环境中进食的生物。这两种策略之间存在权衡（即生物获取食物和消化食物的速度之间呈负相关关系），这是许多生态模型的一个关键假设。在这里，我们评估了从单细胞纳米鞭毛虫到属于水生和陆生领域的大型哺乳动物等各种异养真核生物之间的这种权衡关系的证据。利用>500 种物种的资源获取和摄取率数据，我们没有发现物种之间存在权衡关系的证据。相反，最大清除率和最大摄取率之间存在正相关关系。这种正相关关系不是由于将不同的分类群混为一谈造成的；它在我们研究的所有生物分组中都成立。纠正体重差异会削弱但不会改变正相关关系，因此这也不是大小缩放的结果。相反，这种正相关关系代表了“生活节奏”中的慢-快梯度，它超过了预期的拾荒者-剥削者权衡关系。因此，其他权衡关系必须塑造生态过程，研究它们可以更深入地了解自然界中的共存、竞争动态和生物多样性模式。一个有潜力的研究目标是生长速度和逃避捕食之间的已有充分记录的权衡关系，它也可以驱动我们在这里观察到的慢-快梯度。
