School of Environmental and Rural Science, University of New England, Armidale, New South Wales, Australia.
Estación Biológica de Doñana (EBD-CSIC), Seville, Spain.
J Anim Ecol. 2023 Mar;92(3):760-773. doi: 10.1111/1365-2656.13889. Epub 2023 Feb 5.
Ecological processes leave distinct structural imprints on the species interactions that shape the topology of animal-plant mutualistic networks. Detecting how direct and indirect interactions between animals and plants are organised is not trivial since they go beyond pairwise interactions, but may get blurred when considering global network descriptors. Recent work has shown that the meso-scale, the intermediate level of network complexity between the species and the global network, can capture this important information. The meso-scale describes network subgraphs representing patterns of direct and indirect interactions between a small number of species, and when these network subgraphs differ statistically from a benchmark, they are often referred to as 'network motifs'. Although motifs can capture relevant ecological information of species interactions, they remain overlooked in natural plant-pollinator networks. By exploring 60 empirical plant-pollinator networks from 18 different studies with wide geographical coverage, we show that some network subgraphs are consistently under- or over-represented, suggesting the presence of worldwide network motifs in plant-pollinator networks. In addition, we found a higher proportion of densely connected network subgraphs that, based on previous findings, could reflect that species relative abundances are the main driver shaping the structure of the meso-scale on plant-pollinator communities. Moreover, we found that distinct subgraph positions describing species ecological roles (e.g. generalisation and number of indirect interactions) are occupied by different groups of animal and plant species representing their main life-history strategies (i.e. functional groups). For instance, we found that the functional group of 'bees' was over-represented in subgraph positions with a lower number of indirect interactions in contrast to the rest of floral visitors groups. Finally, we show that the observed functional group combinations within a subgraph cannot be retrieved from their expected probabilities (i.e. joint probability distributions), indicating that plant and floral visitor associations within subgraphs are not random either. Our results highlight the presence of common network motifs in plant-pollinator communities that are formed by a non-random association of plants and floral visitors functional groups.
生态过程在塑造动植物互惠网络拓扑结构的物种相互作用中留下了明显的结构印记。检测动植物之间的直接和间接相互作用是如何组织的并不简单，因为它们超出了两两相互作用的范围，但在考虑全局网络描述符时可能会变得模糊。最近的研究表明，中间尺度（物种和全局网络之间的网络复杂性的中间水平）可以捕获这些重要信息。中间尺度描述了代表少数物种之间直接和间接相互作用模式的网络子图，当这些网络子图在统计上与基准不同时，它们通常被称为“网络基元”。尽管基元可以捕获物种相互作用的相关生态信息，但它们在自然植物传粉者网络中仍然被忽视。通过探索来自 18 项不同研究的 60 个具有广泛地理覆盖范围的实证植物传粉者网络，我们表明一些网络子图始终被低估或高估，这表明植物传粉者网络中存在全球性的网络基元。此外，我们发现了更多密集连接的网络子图，根据先前的发现，这可能反映出物种相对丰度是塑造植物传粉者群落中间尺度结构的主要驱动力。此外，我们发现描述物种生态角色（例如概括和间接相互作用的数量）的不同子图位置被不同的动物和植物物种组占据，代表了它们的主要生活史策略（即功能组）。例如，我们发现与其他花卉访客群体相比，“蜜蜂”功能组在间接相互作用数量较低的子图位置上被高估。最后，我们表明，在子图内观察到的功能组组合不能从它们的预期概率（即联合概率分布）中检索到，这表明子图内的植物和花卉访客关联也不是随机的。我们的研究结果强调了植物传粉者群落中常见网络基元的存在，这些基元是由植物和传粉者功能组的非随机关联形成的。
