RESOURCE COMPETITION IN A VARIABLE ENVIRONMENT - PHYTOPLANKTON GROWING ACCORDING TO MONODS MODEL
RESOURCE COMPETITION IN A VARIABLE ENVIRONMENT - PHYTOPLANKTON GROWING ACCORDING TO MONODS MODEL
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DOI：
10.1086/285131
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发表时间：
1990-12-01
影响因子：
2.9
通讯作者：
GROVER, JP
中科院分区：
文献类型：
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作者：
GROVER, JP
种间竞争的理论模型通常假设种群和资源动态平衡，这一假设经常受到批评。假设偏离平衡是为了减少种间竞争，促进共存。当两种藻类之间对同一资源的竞争使用Monod方程建模时，当资源以周期脉冲形式供应时，如果第二个竞争者具有更高的最大生长速率，那么在平衡状态下获胜的物种通常不会获胜。对于典型的氮磷限制的模型参数，这种选择对最高生长速率高的物种是强烈的。对藻类竞争的实验室研究的回顾在很大程度上对这一预测没有定论。然而，理论提出了两个理由来怀疑对具有最高生长速率的物种的选择在自然界中是通过这种机制发生的。首先，当资源供应的可变性以正弦波动而不是脉冲的形式出现时，对最高增长率高的物种的选择是弱的。其次，当发生细胞内资源储存时，对最高生长速率高的物种的选择也较弱。在这两种情况下，藻类在平衡状态下的优势竞争对手在非平衡状态下也会成为优势竞争对手。在所有测试条件下，两个竞争者在一种资源上共存的情况比竞争排斥的情况更少见。然而，缺乏平衡可能是在更复杂的生态系统中物种多样性的一个可能的解释，这些生态系统具有不止一种资源，或者不止一个营养水平，在自然界中几乎是普遍存在的。
Theoretical models of interspecific competition often assume equilibrium in population and resource dynamics, an assumption that is often criticized. Departures from equilibrium are hypothesized to reduce interspecific competition and facilitate coexistence. When competition between two algae for one resource is modeled using Monod equations, the species that wins at equilibrium does not usually win when resources are supplied as periodic pulse, if the second competitor has the higher maximal growth rate. For model parameters typical of nitrogen and phosphorus limitation, this selection for species with high maximal growth rates is strong. A review of laboratory studies of algal competition is largely inconclusive concerning this prediction. Theory suggests, however, two reasons to doubt that selection for species with high maximal growth rates occurs by this mechanism in nature. First, when variability in resource supply occurs as sinusoidal fluctuations, rather than as pulses, selection for species with high maximal growth rates is weak. Second, when intracellular storage of resources occurs, selection for species with high maximal growth rates is also weak. Under either of these conditions, it is common for algae that are superior competitors at equilibrium to be superior competitors under nonequilibrium conditions also. Under all conditions tested, coexistence of two competitors on one resource is less common than competitive exclusion. Lack of equilibrium may, however, be a likely explanation for species diversity in the more complicated ecosystems with more than one resource, or more than one trophic level, that are nearly universal in nature.