Build-up mechanisms determining the topology of mutualistic networks.
The frequency distribution of the number of interactions per species (i.e., degree distribution) within plant-animal mutualistic assemblages often decays as a power-law with an exponential truncation. Such a truncation suggests that there are ecological factors limiting the frequency of supergeneralist species. However, it is not clear whether these patterns can emerge from intrinsic features of the interacting assemblages, such as differences between plant and animal species richness (richness ratio). Here, we show that high richness ratios often characterize plant-animal mutualisms. Then, we demonstrate that exponential truncations are expected in bipartite networks generated by a simple model that incorporates build-up mechanisms that lead to a high richness ratio. Our results provide a simple interpretation for the truncations commonly observed in the degree distributions of mutualistic networks that complements previous ones based on biological effects.
Guimarães
Paulo R
PR
Programa de Pós-graduação em Ecologia, Insituto de Biologia, Universidade Estadual de Campinas 6109, 13083-970 Campinas, SP, Brazil. prguima@ifi.unicamp.br
Machado
Glauco
G
de Aguiar
Marcus A M
MA
Jordano
Pedro
P
Bascompte
Jordi
J
Pinheiro
Aluísio
A
Dos Reis
Sérgio Furtado
SF
D000818:Animals; D017753:Ecosystem; D020387:Food Chain; D008954:Models, Biological; D018521:Plant Physiological Phenomena; D012098:Reproduction; D012639:Seeds; D013045:Species Specificity