Journal of Animal Ecology 2004 73, 1102–1114 © 2004 British Ecological Society Blackwell Publishing, Ltd. Experimental demonstration of species coexistence enabled by dispersal limitation DOUGLAS W. YU*, HOWARD B. WILSON†, MEGAN E. FREDERICKSON‡, WILY PALOMINO§, RAFAEL DE LA COLINA§, DAVID P. EDWARDS* and ANGEL A. BALARESO¶ *School of Biological Sciences and Centre for Ecology, Evolution, and Conservation Biology (CEEC), University of East Anglia, Norwich, Norfolk NR4 7TJ, UK; †Department of Biology, Imperial College at Silwood Park, Ascot, Berks SL5 7PY, UK; ‡Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA; § Herbario Vargas, Universidad Nacional de San Antonio Abad de Cusco, Cusco, Perú; and ¶ Sachavacayoc, Tambopata, Madre de Dios, Perú Summary 1. Dispersal limitation is widely invoked to explain species coexistence and cooperation in the face of competition and cheating. However, empirical evidence from natural eco- systems for the stabilizing effect of space is sparse. 2. We use a Neotropical ant–plant and its ant symbionts to show how mutual dispersal limitation brings about the stable persistence of coexistence and mutualism. 3. We demonstrate that two ant genera exhibit hierarchies in competitive ability, fecund- ity and dispersal ability, which suggests that a competition–colonization trade-off could be producing coexistence. However, we also show that this trade-off is not a suf- ficient explanation for coexistence. 4. Instead, we provide evidence that a dispersal–fecundity trade-off stabilizes the system by making each genus more dispersal-limited in a different portion of the environment. In this way, dispersal limitation can be seen as a form of environmental niche partitioning. 5. We also find that regeneration niche partitioning and a competition–colonization trade-off may help to bring about local mixing. 6. This study shows that care needs to be taken in identifying the critical mechanisms producing coexistence. Trade-offs between different stages of colonization may be more important for explaining coexistence than any trade-offs between competitive ability and colonization rate. Key-words: habitat destruction hypothesis, metacommunity, mutualism, myrmecophyte, recruitment limitation, spatial ecology. Journal of Animal Ecology (2004) 73, 1102–1114 Introduction A major innovation in population biology over the pre- vious decade has been the incorporation of space into models of competition, predation and cooperation (Tilman & Kareiva 1997; Dieckmann, Law & Metz 2000). The most influential model has been the com- petition–colonization trade-off (Levins & Culver 1971; Tilman 1994; Rees et al . 2001). However, the model’s ability to explain coexistence in real systems remains empirically unestablished (Harrison, Thomas & Lewinsohn 1995; Wennergren, Ruckelshaus & Kareiva 1995; Adler & Mosquera 2000; Yu & Wilson 2001; Levine & Rees 2002), due to the logistical challenges of defining spatial structure, measuring dispersal, and assembling the requisite large sample sizes. In addition, one must also consider alternative explanations, such as resource niche partitioning (Comins & Noble 1985; Tilman & Pacala 1993; Pacala & Tilman 1994; Chesson 2000; Rees et al . 2001; Yu & Wilson 2001), recruitment limitation (Hurtt & Pacala 1995; Bolker & Pacala 1999), and negative density dependence caused by natural enemies (Connell, Tracey & Webb 1984). Thus, the challenge these days is identifying which mechanisms most contribute to Correspondence: Douglas Yu, School of Biological Sciences, University of East Anglia, Norwich, Norfolk NR4 7TJ, UK. Fax: 01603 593 250; E-mail: douglas.yu@uea.ac.uk