Abstract

The degree distribution of the plant-pollinator network was identified by analyzing the data in the ecosystem and reproduced by a model of the growing bipartite mutualistic networks. The degree distribution of pollinator shows power law or stretched exponential distribution, while plant usually shows stretched exponential distribution. In the growth model, the plant and the pollinator are selected with probability Pp and PA=1–Pp, respectively. The number of incoming links for the plant and the pollinator is lp and lA, respectively. The probability that the link of the plant selects the pollinator of the existing network given as Aki =kλiA/∑ikλiA , and the probability that the pollinator selects the plant is Pki=kλip/∑ikλip. When the nonlinear growth index is λχ=1 (Χ=A or P), the degree distribution follows a power law, and if 0≤λχ<1, the degree distribution follows a stretched exponential distribution. The cumulative degree distributions of plants and pollinators of 14 empirical plant-pollinators included in Interaction Web Database were calculated. A set of parameters (PA,PP,lA,lP) that reproduces these cumulative degree distributions and a growth index λχ=1 (Χ=A or P) were obtained. We found that animal takes very heterogenous connections, whereas plant takes a more flexible connection network.