Complex webs of interactions in ecosystems rely on a few key species

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A team led by Jordi Bascompte, an ecologist at the Doñana Biological Station in Spain, looked at how the complex network of interactions between plants and their pollinators and seed dispersers within a community affects biodiversity. Source: Nature 458, 1018–1020 (23 April 2009)

The work focused on the mutually beneficial interaction and their patterns of relationship of entire communities composes by all plant species and all insect pollinators or seed dispersers. Dr. Bascompte’s paper tries to understand for the first time what are the implications for biodiversity persistence of those web patterns.

The patterns of these networks of ecological interactions are the ones that minimize competition, for instance between plants for common resources (water, light, nutrients). Those ecosystems allow the co-existence of the higher number of species.

If one species go extintc, will this extinction be amplifying through a cascade of co-extinction through the entire ecosystem? They way these complex networks of interactions are organized makes them robust to the random extinction of species except if the network relies very much on a few species with a high number of interactions that are they connected keeping all the network together. If one of species disappearing is one the key ones, then the network collapse very fast. So the network is on one hand very robust to random extinctions but is very vulnerable if these few key species are the ones going extinct.

Current theories of biodiversity don’t take those of networks into account, only pairwise interactions on the facts of for instance one plant and one insect pollinator.Jordi Bascompte’s work is relevant in that climate change is decreasing biodiversity. It is important to understand just how vulnerable are complex ecosystems.

Ecology as a science is now  learning to look at the greater picture, like molecular biologists evolved from usually targeting a specific gene and understanding the products of that gene a few years go to nowadays trying to work out what is the implication of a gene for the entire network of the gene pool.

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