Species reintroductions can be used as a conservation strategy to restore ecological interactions and the functionality of impoverished ecosystems. The ecological effects of reintroductions go beyond restoring pairwise interactions, because reintroductions can change how extant species are indirectly linked to each other in an ecological community. These indirect pathways, in turn, may shape a myriad of ecological and evolutionary processes operating in ecological systems. Here, we investigated how reintroductions may affect the direct and indirect pathways connecting species in ecological networks. We modeled the potential effects of the reintroduction of four frugivore species (channel-billed toucans, red-humped agoutis, brown howler monkeys and yellow-footed tortoises) to the local seed dispersal network in an Atlantic Forest site, the Tijuca National Park (Rio de Janeiro, Brazil). We used a seed dispersal interaction dataset together with data on species occurrences in Tijuca to build network models. Then, we calculated how network structure and the total amount of indirect effects varied across simulated networks with and without the reintroduced species. Using random reintroduction simulations, we tested if the observed network changes were expected merely from the increase in species richness. The reintroduction of the frugivore species increased network connectance, nestedness, robustness, number of pathways and total amount of indirect effects in all simulated networks. The increase in number of pathways with the addition of the four reintroduced species was greater than the sum of isolated effects for each species, because some interaction pathways contained several reintroduced species. These changes in network metrics were significantly greater than if a randomly chosen set of four species was reintroduced. Furthermore, our results indicate that multiple reintroductions in the same area, known as refaunation, may have an even greater restoration effect than single species reintroductions through increased indirect connections in the network.

中文翻译：

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热带野化通过直接和间接的网络效应使热带社区受益

物种重新引入可用作恢复生态相互作用和贫困生态系统功能的保护策略。重新引入的生态影响不仅仅是恢复成对的相互作用，因为重新引入可以改变生态群落中现存物种之间的间接联系方式。反过来，这些间接途径可能会塑造在生态系统中运行的无数生态和进化过程。在这里，我们研究了重新引入如何影响生态网络中连接物种的直接和间接途径。我们模拟了重新引入四种食果动物物种（沟嘴巨嘴鸟、红脊刺豚鼠、棕吼猴和黄脚陆龟）对大西洋森林地区当地种子传播网络的潜在影响，蒂茹卡国家公园（巴西里约热内卢）。我们使用种子传播交互数据集和蒂茹卡的物种发生数据来构建网络模型。然后，我们计算了网络结构和间接影响的总量如何在有和没有重新引入物种的模拟网络中变化。使用随机重新引入模拟，我们测试了观察到的网络变化是否仅来自物种丰富度的增加。食果动物物种的重新引入增加了所有模拟网络中的网络连接性、嵌套性、鲁棒性、路径数量和间接影响的总量。添加四种重新引入的物种后途径数量的增加大于每个物种的孤立效应的总和，因为一些相互作用途径包含几个重新引入的物种。网络指标的这些变化明显大于重新引入随机选择的四个物种的集合。此外，我们的结果表明，通过增加网络中的间接连接，在同一地区多次重新引入（称为重新动物区系）可能比单一物种重新引入具有更大的恢复效果。