Jordi Bascompte on Mutualistic Networks

by Noam Ross, 15 November 2012


Jordi Bascompte gave a Storer Lecture at UC Davis on November 15, 2012. Here are my rough notes:

  • Biodiversity as the set of interactions between species, rather than accounting of species
  • Most research in mutualism in evolution focus on bilateral interactions (e.g., Darwin’s orchids and moths)
  • Jordi’s goal is to use network theory to represent mutualism in ecological communities and generalize about them. Three

  • Using data sets on man mutualistic communities (pollinators, frugivores),

    1. Describe network archiecture
    2. Examine robustness against extinctions, and relationship of network to species richness
    3. Examine the contribution of individual species to network architecture and robustness

Major results

  • Networks tend to have nested architectures (Bascompte et al. 2003)
  • Nested structures are more robust to species extinctions, if specialists have greater risk of extinction (Memmott et al. 2004)
  • Phylogeny predicts a lot of mutualistic network structure. As a result, network-driven extinction patterns tend to cluster on the phylogenetic tree, causing a greater loss of taxonomic diversity than would occur in a random network (Rezende et al. 2007)
  • Theoretical result: nested networks have lower effective interspecific competition, allowing higher maximum biodiversity (Bastolla et al. 2009)
  • There’s a wide range of the extent that plants actually contribute to the nested network architecture. However those that contribute heavily to nestedness have a higher probability of going extinct. Economic systems can be described in similar ways, and you get the same results for designers and contractors in industry (Saavedra et al. 2011). However, the mechanism driving this pattern is not known
    • is it general to nested networks, or a consequence of how these networks have evolved

Idea: you could compare randomly generated networks to real or simulated phylogenetically ones, and see the strength of the contribution-vulnerability trade-off

Aside: When you look at strength of network interactions, you see a similar pattern of asymmetry and nestedness in networks.

References

Bascompte, J., P. Jordano, C. J. Melián, and J. M. Olesen. 2003. The nested assembly of plant-animal mutualistic networks.. Proceedings of the National Academy of Sciences of the United States of America 100:9383–7.

Bastolla, U., M. a Fortuna, A. Pascual-García, A. Ferrera, B. Luque, and J. Bascompte. 2009. The architecture of mutualistic networks minimizes competition and increases biodiversity.. Nature 458:1018–20.

Memmott, J., N. M. Waser, and M. V. Price. 2004. Tolerance of pollination networks to species extinctions.. Proceedings. Biological sciences / The Royal Society 271:2605–11.

Rezende, E. L., J. E. Lavabre, P. R. Guimarães, P. Jordano, and J. Bascompte. 2007. Non-random coextinctions in phylogenetically structured mutualistic networks.. Nature 448:925–8.

Saavedra, S., D. B. Stouffer, B. Uzzi, and J. Bascompte. 2011. Strong contributors to network persistence are the most vulnerable to extinction.. Nature 478:233–5.