The Functional Consequences of Mutualistic Network Architecture

The architecture and properties of many complex networks play a significant role in the functioning of the systems they describe. Recently, complex network theory has been applied to ecological entities, like food webs or mutualistic plant-animal interactions. Unfortunately, we still lack an accurate view of the relationship between the architecture and functioning of ecological networks. In this study we explore this link by building individual-based pollination networks from eight Erysimum mediohispanicum (Brassicaceae) populations. In these individual-based networks, each individual plant in a population was considered a node, and was connected by means of undirected links to conspecifics sharing pollinators. The architecture of these unipartite networks was described by means of nestedness, connectivity and transitivity. Network functioning was estimated by quantifying the performance of the population described by each network as the number of per-capita juvenile plants produced per population. We found a consistent relationship between the topology of the networks and their functioning, since variation across populations in the average per-capita production of juvenile plants was positively and significantly related with network nestedness, connectivity and clustering. Subtle changes in the composition of diverse pollinator assemblages can drive major consequences for plant population performance and local persistence through modifications in the structure of the inter-plant pollination networks.

This work was supported by MARM grant (078/2007), CYTED (409AC0369), and Consolider-Ingenio Montes (CSD2008-00040) to JMG, the Spanish Ministry of Education and Science (CGL2009-07015 to FP and CGL2006-00373 to PJ), and by the Junta de Andalucía (RNM220 to JMG, CV165 to FP, P07-RNM2824 to PJ). Our collaborative work is supported by the Unidad Asociada CSIC-UGR “Grupo de Ecología, Genética y Coevolución.”