The modularity of seed dispersal: differences in structure and robustness between bat– and bird–fruit networks
The modularity of seed dispersal: differences in structure and robustness between bat– and bird–fruit networks
复制标题
种子传播的模块化：蝙蝠和鸟类果实网络之间结构和鲁棒性的差异
作者：
M. Mello;F. M. Marquitti;P. Guimarães;E. Kalko;P. Jordano;M. D. Aguiar
在植物-动物互惠网络中，不同的动物群体优先与不同的植物相互作用，从而形成负责不同部分服务的不同模块。然而，我们目前对种子传播网络的了解仅基于鸟类。因此，我们希望通过研究蝙蝠-水果网络并测试它们与鸟类-水果网络的区别来填补这一空白。由于新热带蝙蝠和鸟类的饮食重叠很低，它们应该在本地网络中形成不同的互利模块。此外，由于frugivory只进化一次之间的新热带区蝙蝠，但几次独立的新热带区鸟类，更大的饮食重叠预计蝙蝠之间，因此连接性和嵌套应该更高的蝙蝠水果网络。如果蝙蝠果网络具有更高的嵌套性和连通性，它们应该对干扰更鲁棒。我们分析了一个蝙蝠和鸟类的混合网络，以及20个完全由蝙蝠（11）或鸟类（9）组成的网络。正如预期的那样，混合网络的结构是模块化的（M = 0.45）和嵌套的（NODF = 0.31）;一个模块只包含鸟类，两个只包含蝙蝠。在20个数据集中，蝙蝠-水果网络（NODF = 0.53 ± 0.09，C = 0.30 ± 0.11）比鸟-水果网络（NODF = 0.42 ± 0.07，C = 0.22 ± 0.09）嵌套程度更高，连接度更高。出乎意料的是，鸟类-水果网络对动物物种灭绝的鲁棒性（R = 0.60 ± 0.13）高于蝙蝠-水果网络（R = 0.54 ± 0.09），差异主要由物种丰富度解释。这些发现表明，模块化结构也发生在种子传播网络，类似于授粉网络。较高的嵌套性和连通性观察蝙蝠水果网络相比，鸟类水果网络可以解释的单系进化的食果性在新热带蝙蝠，其中专家的饮食似乎已经从游泳池的水果消费的通才。
In networks of plant–animal mutualisms, different animal groups interact preferentially with different plants, thus forming distinct modules responsible for different parts of the service. However, what we currently know about seed dispersal networks is based only on birds. Therefore, we wished to fill this gap by studying bat–fruit networks and testing how they differ from bird–fruit networks. As dietary overlap of Neotropical bats and birds is low, they should form distinct mutualistic modules within local networks. Furthermore, since frugivory evolved only once among Neotropical bats, but several times independently among Neotropical birds, greater dietary overlap is expected among bats, and thus connectance and nestedness should be higher in bat–fruit networks. If bat–fruit networks have higher nestedness and connectance, they should be more robust to extinctions. We analyzed 1 mixed network of both bats and birds and 20 networks that consisted exclusively of either bats (11) or birds (9). As expected, the structure of the mixed network was both modular (M = 0.45) and nested (NODF = 0.31); one module contained only birds and two only bats. In 20 datasets with only one disperser group, bat–fruit networks (NODF = 0.53 ± 0.09, C = 0.30 ± 0.11) were more nested and had a higher connectance than bird–fruit networks (NODF = 0.42 ± 0.07, C = 0.22 ± 0.09). Unexpectedly, robustness to extinction of animal species was higher in bird–fruit networks (R = 0.60 ± 0.13) than in bat–fruit networks (R = 0.54 ± 0.09), and differences were explained mainly by species richness. These findings suggest that a modular structure also occurs in seed dispersal networks, similar to pollination networks. The higher nestedness and connectance observed in bat–fruit networks compared with bird–fruit networks may be explained by the monophyletic evolution of frugivory in Neotropical bats, among which the diets of specialists seem to have evolved from the pool of fruits consumed by generalists.