There’s a 2-page “Author summary” in the print issue, the main article is online as PNAS Plus.
Watson, J.R., D.A. Siegel, B.E. Kendall, S. Mitarai, A. Rassweiller, and S. D. Gaines. 2011. Identifying critical regions in small-world marine metapopulations. Proceedings of the National Academy of Sciences of the USA 108: 17583-17584, E907-E913.