Instituto Argentino de Investigaciones de las Zonas Aridas, CONICET, CC 507, 5500 Mendoza, Argentina.
Ecology. 2012 Apr;93(4):719-25. doi: 10.1890/11-1356.1.
Recent studies of plant-animal mutualistic networks have assumed that interaction frequency between mutualists predicts species impacts (population-level effects), and that field estimates of interaction strength (per-interaction effects) are unnecessary. Although existing evidence supports this assumption for the effect of animals on plants, no studies have evaluated it for the reciprocal effect of plants on animals. We evaluate this assumption using data on the reproductive effects of pollinators on plants and the reciprocal reproductive effects of plants on pollinators. The magnitude of species impacts of plants on pollinators, the reciprocal impacts of pollinators on plants, and their asymmetry were well predicted by interaction frequency. However, interaction strength was a key determinant of the sign of species impacts. These results underscore the importance of quantifying interaction strength in studies of mutualistic networks. We also show that the distributions of interaction strengths and species impacts are highly skewed, with few strong and many weak interactions. This skewed distribution matches the pattern observed in food webs, suggesting that the community-wide organization of species interactions is fundamentally similar between mutualistic and antagonistic interactions. Our results have profound ecological implications, given the key role of interaction strength for community stability.
最近对动植物互惠网络的研究假设，互惠者之间的相互作用频率可以预测物种的影响（种群水平的效应），并且不需要对相互作用强度进行实地估计（每次相互作用的效应）。尽管现有证据支持这种动物对植物的影响的假设，但没有研究评估它对植物对动物的互惠影响。我们使用关于传粉者对植物的繁殖影响以及植物对传粉者的互惠繁殖影响的数据来评估这一假设。植物对传粉者的物种影响的大小、传粉者对植物的互惠影响的大小及其不对称性都可以很好地由相互作用频率来预测。然而，相互作用强度是物种影响的方向的关键决定因素。这些结果强调了在互惠网络研究中量化相互作用强度的重要性。我们还表明，相互作用强度和物种影响的分布高度偏态，只有少数强相互作用，而许多弱相互作用。这种偏态分布与食物网中观察到的模式相匹配，这表明在互惠和拮抗相互作用之间，物种相互作用的群落组织在根本上是相似的。鉴于相互作用强度对群落稳定性的关键作用，我们的研究结果具有深远的生态意义。
