James et al. (2012) presented simulations that apparently falsify the analytical result by Bastolla et al. (2009), who showed that nested mutualistic interactions decrease interspecific competition and increase biodiversity in model ecosystems. This contradiction, however, mainly stems from the incorrect application of formulas derived for fully connected networks to empirical, sparse networks.
@article{arxiv.1301.3651,
title = {Nestedness in mutualistic networks},
author = {Rudolf P. Rohr and Miguel A. Fortuna and Bartolo Luque and Jordi Bascompte},
journal= {arXiv preprint arXiv:1301.3651},
year = {2013}
}