The architecture of mutualistic networks minimizes competition and increases biodiversity

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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.

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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.


  1. 1

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

  2. 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)

  3. 3

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

  4. 4

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

  5. 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)

  6. 6

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

  7. 7

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

  8. 8

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

  9. 9

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

  10. 10

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

  11. 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)

  12. 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)

  13. 13

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

  14. 14

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

  15. 15

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

  16. 16

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

  17. 17

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

  18. 18

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

  19. 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)

  20. 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)

  21. 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)

  22. 22

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

  23. 23

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

  24. 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)

  25. 25

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

  26. 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)

  27. 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)

  28. 28

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

  29. 29

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

  30. 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)

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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.

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Correspondence to Jordi Bascompte.

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

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Bastolla, U., Fortuna, M., Pascual-García, A. et al. The architecture of mutualistic networks minimizes competition and increases biodiversity. Nature 458, 1018–1020 (2009) doi:10.1038/nature07950

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