Data from: Coevolution and the architecture of mutualistic networks

Although coevolution is widely recognized as an important evolutionary process for pairs of reciprocally specialized species, its importance within species-rich communities of generalized species has been questioned. Here we develop and analyze mathematical models of mutualistic communities, such as those between plants and pollinators or plants and seed-dispersers to evaluate the importance of coevolutionary selection within complex communities. Our analyses reveal that coevolutionary selection can drive significant changes in trait distributions with important consequences for the network structure of mutualistic communities. One such consequence is greater connectance caused by an almost invariable increase in the rate of mutualistic interaction within the community. Another important consequence is altered patterns of nestedness. Specifically, interactions mediated by a mechanism of phenotype matching tend to be anti-nested when coevolutionary selection is weak and even more strongly anti-nested as increasing coevolutionary selection favors the emergence of reciprocal specialization. In contrast, interactions mediated by a mechanism of phenotype differences tend to be nested when coevolutionary selection is weak, but less nested as increasing coevolutionary selection favors greater levels of generalization in both plants and animals. Taken together, our results show that coevolutionary selection can be an important force within mutualistic communities, driving changes in trait distributions, interaction rates, and even network structure.尽管协同进化（coevolution）作为互惠特化物种种对的重要进化过程已得到广泛认可，但它在广适性物种组成的物种丰富群落中的重要性却受到了质疑。本文构建并分析了互利共生群落（mutualistic communities）的数学模型——例如植物与传粉者、植物与种子传播者之间的群落——以评估协同进化选择在复杂群落中的重要性。我们的分析表明，协同进化选择可显著改变性状分布（trait distributions），进而对互利共生群落的网络结构产生重要影响。其中一项结果是，群落内互利互作速率近乎恒定的提升会带来更高的连接度（connectance）。另一项重要结果是嵌套性（nestedness）模式发生改变。具体而言，由表型匹配（phenotype matching）机制介导的互作，在协同进化选择较弱时往往呈反嵌套（anti-nested）结构，且随着协同进化选择增强，互惠特化的出现会进一步加剧反嵌套程度。与之相反，由表型差异（phenotype differences）机制介导的互作，在协同进化选择较弱时往往呈嵌套结构，但随着协同进化选择增强，动植物双方的泛化程度均得以提升，此时嵌套程度会降低。综上，我们的研究结果表明，协同进化选择可成为互利共生群落中的重要进化动力，驱动性状分布、互作速率乃至网络结构发生改变。