Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Letter
  • Published:

The architecture of mutualistic networks minimizes competition and increases biodiversity


The main theories of biodiversity either neglect species interactions1,2 or assume that species interact randomly with each other3,4. However, recent empirical work has revealed that ecological networks are highly structured5,6,7, and the lack of a theory that takes into account the structure of interactions precludes further assessment of the implications of such network patterns for biodiversity. Here we use a combination of analytical and empirical approaches to quantify the influence of network architecture on the number of coexisting species. As a case study we consider mutualistic networks between plants and their animal pollinators or seed dispersers5,8,9,10,11. These networks have been found to be highly nested5, with the more specialist species interacting only with proper subsets of the species that interact with the more generalist. We show that nestedness reduces effective interspecific competition and enhances the number of coexisting species. Furthermore, we show that a nested network will naturally emerge if new species are more likely to enter the community where they have minimal competitive load. Nested networks seem to occur in many biological and social contexts12,13,14, suggesting that our results are relevant in a wide range of fields.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Figure 1: The structure of mutualistic networks determines the number of coexisting species.
Figure 2: The nested architecture of real mutualistic networks increases their biodiversity.

Similar content being viewed by others


  1. Alonso, D., Etienne, R. S. & McKane, A. J. The merits of neutral theory. Trends Ecol. Evol. 21, 451–457 (2006)

    Article  Google Scholar 

  2. Volkov, I., Banavar, J. R., Hubbell, S. P. & Maritan, A. Patterns of relative species abundance in rainforests and coral reefs. Nature 450, 45–49 (2007)

    Article  ADS  CAS  Google Scholar 

  3. May, R. M. Stability and Complexity of Model Ecosystems (Princeton Univ. Press, 1974)

    Google Scholar 

  4. Chesson, P. Mechanisms of maintenance of species diversity. Annu. Rev. Ecol. Syst. 31, 343–366 (2000)

    Article  Google Scholar 

  5. Bascompte, J., Jordano, P., Melián, C. J. & Olesen, J. M. The nested assembly of plant-animal mutualistic networks. Proc. Natl Acad. Sci. USA 100, 9383–9387 (2003)

    Article  ADS  CAS  Google Scholar 

  6. Montoya, J. M., Pimm, S. L. & Solé, R. V. Ecological networks and their fragility. Nature 442, 259–264 (2006)

    Article  ADS  CAS  Google Scholar 

  7. Pascual, M. & Dunne, J. A. (eds) Ecological Networks: Linking Structure to Dynamics in Food Webs (Oxford Univ. Press, 2006)

    MATH  Google Scholar 

  8. Jordano, P., Bascompte, J. & Olesen, J. M. Invariant properties in coevolutionary networks of plant-animal interactions. Ecol. Lett. 6, 69–81 (2003)

    Article  Google Scholar 

  9. Vázquez, D. P. & Aizen, M. A. Asymmetric specialization: a pervasive feature of plant-pollinator interactions. Ecology 85, 1251–1257 (2004)

    Article  Google Scholar 

  10. Bascompte, J., Jordano, P. & Olesen, J. M. Asymmetric coevolutionary networks facilitate biodiversity maintenance. Science 312, 431–433 (2006)

    Article  ADS  CAS  Google Scholar 

  11. Olesen, J. M., Bascompte, J., Dupont, Y. L. & Jordano, P. The modularity of pollination networks. Proc. Natl Acad. Sci. USA 104, 19891–19896 (2007)

    Article  ADS  CAS  Google Scholar 

  12. Guimarães, P. R., Sazima, C., Furtado dos Reis, S. & Sazima, I. The nested structure of marine cleaning symbiosis: is it like flowers and bees? Biol. Lett. 3, 51–54 (2007)

    Article  Google Scholar 

  13. May, R. M., Levin, S. A. & Sugihara, G. Ecology for bankers. Nature 451, 893–895 (2008)

    Article  ADS  CAS  Google Scholar 

  14. Saavedra, S., Reed-Tsochas, F. & Uzzi, B. A simple model of bipartite cooperation for ecological and organizational networks. Nature 457, 463–466 (2009)

    Article  ADS  CAS  Google Scholar 

  15. Sugihara, G. Niche Hierarchy: Structure Assembly and Organization in Natural Communities. PhD thesis, Princeton Univ. (1982)

    MATH  Google Scholar 

  16. Sugihara, G. Graph theory, homology and food webs. Proc. Symp. Appl. Math. 30, 83–101 (1984)

    Article  MathSciNet  Google Scholar 

  17. Wright, D. H. A simple, stable model of mutualism incorporating handling time. Am. Nat. 134, 664–667 (1989)

    Article  Google Scholar 

  18. Pachepsky, E., Taylor, T. & Jones, S. Mutualism promotes diversity and stability in a simple artificial ecosystem. Artif. Life 8, 5–24 (2002)

    Article  Google Scholar 

  19. Tokita, K. & Yasutomi, A. Emergence of a complex and stable network in a model ecosystem with extinction and mutation. Theor. Popul. Biol. 63, 131–146 (2003)

    Article  Google Scholar 

  20. Rikvold, P. A. & Zia, R. K. P. Punctuated equilibria and 1/f noise in a biological coevolution model with individual-base dynamics. Phys. Rev. E 68, 031913 (2003)

    Article  ADS  Google Scholar 

  21. Memmott, J., Waser, N. M. & Price, M. V. Tolerance of pollinator networks to species extinctions. Proc. R. Soc. Lond. B 271, 2605–2611 (2004)

    Article  Google Scholar 

  22. Fortuna, M. A. & Bascompte, J. Habitat loss and the structure of plant-animal mutualistic networks. Ecol. Lett. 9, 281–286 (2006)

    Article  Google Scholar 

  23. Burgos, E. et al. Why nestedness in mutualistic networks? J. Theor. Biol. 249, 307–313 (2007)

    Article  MathSciNet  Google Scholar 

  24. Rezende, E. L., Lavabre, J. E., Guimarães, P. R., Jordano, P. & Bascompte, J. Nonrandom coextinctions in phylogenetically structured mutualistic networks. Nature 448, 925–928 (2007)

    Article  ADS  CAS  Google Scholar 

  25. Okuyama, T. & Holland, J. N. Network structural properties mediate the stability of mutualistic networks. Ecol. Lett. 11, 208–216 (2008)

    Article  Google Scholar 

  26. Bastolla, U., Lässig, M., Manrubia, S. C. & Valleriani, A. Biodiversity in model ecosystems, I: coexistence conditions for competing species. J. Theor. Biol. 235, 521–530 (2005)

    Article  MathSciNet  Google Scholar 

  27. Bastolla, U., Lässig, M., Manrubia, S. C. & Valleriani, A. Biodiversity in model ecosystems, II: species assembly and food web structure. J. Theor. Biol. 235, 531–539 (2005)

    Article  MathSciNet  Google Scholar 

  28. Lieberman, E., Hauert, C. & Nowak, M. A. Evolutionary dynamics on graphs. Nature 433, 312–316 (2005)

    Article  ADS  CAS  Google Scholar 

  29. Holland, J. N., Okuyama, T. & DeAngelis, D. L. Comment on “Asymmetric coevolutionary networks facilitate biodiversity maintenance”. Science 313, 1887 (2006)

    Article  ADS  CAS  Google Scholar 

  30. Atmar, W. & Patterson, B. D. The measure of order and disorder in the distribution of species in fragmented habitat. Oecologia 96, 373–382 (1993)

    Article  Google Scholar 

Download references


Acknowledgments We thank P. Jordano and J. Olesen for providing data and insight, A. Ramirez Ortiz for discussions and P. Buston and D. Stouffer for comments on a previous draft. J. Olesen provided the drawings in Fig. 1. Funding was provided by the Spanish Ministry of Science and Technology (through a Ramon y Cajal Contract and a Consolider Ingenio Project to U.B., a PhD Fellowship to M.A.F. and a grant to B.L.) and by the European Heads of Research Councils, the European Science Foundation, and the EC Sixth Framework Programme through a European Young Investigator Award (J.B.). Research at the Centro de Biología Molecular Severo Ochoa is facilitated by an institutional grant from the Ramón Areces Foundation.

Author Contributions U.B., jointly with A.P.-G., A.F. and B.L., performed the analytical development. M.A.F. analysed the real data and, jointly with B.L., performed the simulations. J.B. compiled the real data and, jointly with U.B., designed the study and wrote the first version of the manuscript.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Jordi Bascompte.

Supplementary information

Supplementary Information

This file contains Supplementary Methods, Supplementary Data, Supplementary Figure 1 with a Legend, Supplementary Table 1 and Supplementary References. (PDF 432 kb)

PowerPoint slides

Rights and permissions

Reprints and permissions

About this article

Cite this article

Bastolla, U., Fortuna, M., Pascual-García, A. et al. The architecture of mutualistic networks minimizes competition and increases biodiversity. Nature 458, 1018–1020 (2009).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing