Cheaters in mutualism networks

Abstract

Mutualism-network studies assume that all interacting species are mutualistic partners and consider that all links are of one kind. However, the influence of different types of links, such as cheating links, on network organization remains unexplored. We studied two flower-visitation networks (Malpighiaceae and Bignoniaceae and their flower visitors), and divide the types of link into cheaters (i.e. robbers and thieves of flower rewards) and effective pollinators. We investigated if there were topological differences among networks with and without cheaters, especially with respect to nestedness and modularity. The Malpighiaceae network was nested, but not modular, and it was dominated by pollinators and had much fewer cheater species than Bignoniaceae network (28% versus 75%). The Bignoniaceae network was mainly a plantcheater network, being modular because of the presence of pollen robbers and showing no nestedness. In the Malpighiaceae network, removal of cheaters had no major consequences for topology. In contrast, removal of cheaters broke down the modularity of the Bignoniaceae network. As cheaters are ubiquitous in all mutualisms, the results presented here show that they have a strong impact upon network topology.

Statistical structure of host–phage interactions

“…We hope and envision that a similar process unfolds here in that the finding of a general pattern in the current dataset will stimulate the collection of more and larger hostphage infection networks to continue to provide a fuller picture of who infects whom across an entire community. In so doing, we caution that data completeness can alter the observed patterns of connectivity and refer readers to a number of recent papers that address this topic (95)(96)(97)(98)(99).…”

Biodiversity, Species Interactions and Ecological Networks in a Fragmented World

“…However, fewer pollinator species in a network does not necessarily compromise the fecundity of all plants, because the outcome depends also on the effectiveness of the pollinators (Perfectti et al, 2009). It can even be beneficial if the most abundant pollinators are the most effective, because other pollinators, which might be less efficient or less specialised pollinators or even nectar and pollen robbers, disappear (Genini et al, 2010). However, according to a supposed positive complexity-stability relationship, fewer species and links in pollination networks lower their disturbance resilience (e.g.…”

Quando um visitante floral é um polinizador?

“…2a-b) e promover a transferência dos grãos de pólen. Estes visitantes são denominados de visitantes ilegítimos, e muitas vezes como trapaceiros, pilhadores e oportunistas (Inouye 1983;Soberon Mainero & Martinez Del Rio 1985;Goulson et al 2007;Genini et al 2010;Amaral Neto 2015). Os exemplos mais clássicos são de insetos que perfuram a base da flor (cálice e/ou corola) por fora para roubar o néctar, sendo muito comum em flores de Bignoniaceae (ex.…”

“…Trabalhos recentes começam a separar os pilhadores e trapaceiros nas redes mutualistas (Irwin et al 2001(Irwin et al , 2010Genini et al 2010). Um belíssimo exemplo de trabalho com esta preocupação foi apresentado por Amaral-Neto (2015) tratando das inferências sobre a estrutura e propriedade das redes de interações ao se identificar os pilhadores e as interações proibidas (i.e., as interações podem não acontecer por desacoplamento fenotípico ou temporal, onde simplesmente as espécies não se encontram no tempo ou espaço).…”

“…Na literatura, no entanto, raramente os trabalhos com abordagem de rede de interação apontam diferenças no status dos vários visitantes, sendo comum a denominação de todos os visitantes como polinizadores (Elberling & Olesen 1999;Basílio et al 2006;Olesen et al 2008;Genini et al 2010;Blüthgen & Klein 2011;King et al 2013). Nossa experiência revela que, desta forma, ocorre uma valorização demasiada em relação aos polinizadores.…”