Disease spread in small-size directed trade networks: the role of hierarchical categories
Disease spread in small-size directed trade networks: the role of hierarchical categories
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DOI：
10.1111/j.1365-2664.2010.01884.x
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发表时间：
2010-12
影响因子：
5.7
通讯作者：
M. Pautasso;Xiang-ming Xu;M. Jeger;T. Harwood;M. Moslonka-Lefebvre;L. Pellis
中科院分区：
文献类型：
--
作者：
M. Pautasso;Xiang-ming Xu;M. Jeger;T. Harwood;M. Moslonka-Lefebvre;L. Pellis
总结1。小规模定向网络与许多生物学应用相关，从元种群到食物网，从运输流到进化树，从家庭内的流行病到新出现的植物病原体（例如疫霉）的爆发。然而，人们对这些网络中的动态过程关注甚少。2. 在园艺贸易中，等级类别的结构变化，即生产者、批发商和零售商的比例，可以影响在这些系统中发生植物流行病的可能性，但目前尚不清楚如何影响。3. 我们在六种网络结构（局部、小世界、随机和无标度（SF）网络，它们的进出度（输入和输出链接的数量）呈正相关、无相关和负相关）中，在四个连接水平上的100个节点的定向网络中，对疾病的传播和建立进行了建模，并研究了层次分类的作用。4. 对于非顺丰网络，进出链路数的相关系数与生产者和零售商的比例负相关，与批发商的比例正相关。考虑到之前报道的进出度相关系数与流行病阈值之间的负相关，增加生产者/零售商和去除批发商可能会使非顺丰网络中的流行病更加困难。对于SF网络，这些关联并不普遍存在，因为在这些结构中，流行病的发展是由枢纽的存在驱动的，而不是由大多数节点的特征驱动的。5. 合成与应用。尽管植物贸易运动对植物流行病和新的植物病原体的出现具有重要意义，但人们对国家内部和国家之间园艺网络的当前接触结构以及这种结构如何变化知之甚少。这些信息对于植物健康监管中的风险评估和管理非常重要。因此，这项研究要求长期收集关于植物生产者、批发商和零售商的数量和分布程度的数据。我们的研究结果表明，植物病害管理应集中在苗圃层次的中间层。这一结果可能也适用于小型定向网络的其他生物学应用。
Summary 1. Small-size, directed networks are relevant for many biological applications, from meta-populations to food webs, from transport flows to evolutionary trees, from epidemics within households to outbreaks of emerging plant pathogens (e.g. Phytophthora ramorum). However, little attention has been paid to dynamic processes in these networks. 2. In the horticultural trade, structural change in hierarchical categories, i.e. the proportion of producers, wholesalers and retailers, can influence the likelihood that plant epidemics will take place in such systems, but it is unclear how. 3. We model disease spread and establishment in directed networks of 100 nodes at four connectance levels in six network structures [local, small-world, random, and scale-free (SF) networks with positive, no, and negative correlation between in- and out-degree (number of incoming and outgoing links)], and study the role of hierarchical categories. 4. For non-SF networks, the correlation coefficient between number of incoming and outgoing links is negatively correlated with the proportion of producers and retailers, and positively correlated with the proportion of wholesalers. Given the previously reported negative correlation between the in–out degree correlation coefficient and the epidemic threshold, adding producers/retailers and removing wholesalers can contribute to making epidemics more difficult in non-SF networks. For SF networks these associations are not generally present, as in these structures epidemic development is driven by the presence of hubs, rather than the features of the majority of the nodes. 5. Synthesis and applications. despite the importance of trade movements of plants for plant epidemics and the emergence of new plant pathogens, little is known about the current contact structure of horticultural networks within and among nations, and about how this is changing. Such information is important for risk assessment and management in plant health regulation. This study thus calls for the long-term collection of data on the number and degree distribution of plant producers, wholesalers and retailers. Our results suggest that plant disease management should focus on the middle-tier of the nursery hierarchy. This result is likely to pertain also to other biological applications of small-size directed networks.