Oikos 118: 122Á130, 2009 doi: 10.1111/j.1600-0706.2008.16751.x, # 2008 The Authors. Journal compilation # 2008 Oikos Subject Editor: Jonathan Shurin. Accepted 4 July 2008 Diversity in a complex ecological network with two interaction types Carlos J. Melia´n, Jordi Bascompte, Pedro Jordano and Vlastimil Krˇivan C. J. Melia´n (
[email protected]), J. Bascompte and P. Jordano, Estacio´n Biolo´gica de Don˜ana, CSIC, Apdo. 1056, ESÁ41080 Sevilla, Spain. Á CJM and V. Krˇivan, National Center for Ecological Analysis and Synthesis, Univ. of California at Santa Barbara, 735 State St., Suite 300, Santa Barbara, CA 93101, USA. VK also at: Dept of Theoretical Ecology, Inst. of Entomology, Biology Center AS CR, Branisˇovska´ 31, 37005 Cˇeske´ Budejovice, Czech Republic. Most studies on ecological networks consider only a single interaction type (e.g. competitive, predatory or mutualistic), and try to develop rules for system stability based exclusively on properties of this interaction type. However, the stability of ecological networks may be more dependent on the way different interaction types are combined in real communities. To address this issue, we start by compiling an ecological network in the Don˜ana Biological Reserve, southern Spain, with 390 species and 798 mutualistic and antagonistic interactions. We characterize network structure by looking at how mutualistic and antagonistic interactions are combined across all plant species. Both the ratio of mutualistic to antagonistic interactions per plant, and the number of basic modules with an antagonistic and a mutualistic interaction are very heterogeneous across plant species, with a few plant species showing very high values for these parameters.