Maths experts question key ecological theory

Jun 20, 2012

Mathematicians at the University of York in the UK and the University of Canterbury in New Zealand say they have disproved a widely accepted theory underpinning the operation of complex networks of interactions in the natural world.

Networks are a powerful way to describe , which typically involve large numbers of species that can exhibit both negative (e.g. competition or predation) and positive (e.g. mutualism) interactions with one another. Recent mathematical and suggested that nestedness -- the tendency for ecological specialists to interact with a subset of the species that also interact with more generalist species -- increases .

But the researchers from the York Centre for Complex Systems Analysis (YCCSA) and the Biomathematics Research Centre at Canterbury say they have proved the reverse is true, using mathematical models based on plant-pollinator networks observed in the wild. The data span the globe, ranging from to the high Arctic, and include species such as and hummingbirds as well as such as bees, wasps and butterflies.

The research is published in the latest edition of Nature.

By carefully examining previous analytic results, and applying computational and statistical methods to 59 empirical datasets representing mutualistic plant-pollinator networks, they say they disprove the accepted theory of nestedness. Instead, they contend that the number of mutualistic partners a species has is a much better predictor of individual and community persistence.

Co-author Dr Jon Pitchford, who is also a member of the Departments of Biology and Mathematics at York, said: "We know that real mutualistic communities are nested -- they have sets of interactions-within-interactions, rather like Russian dolls. We are trying to understand how this is related to their biodiversity and stability. This will enable us to better understand the way ecological networks are affected by environmental fluctuation and climate change."

Co-author Dr Alex James, of the Department of Mathematics and Statistics at Canterbury, said: "It is a well-used phrase but correlation does not imply causation. Although a cursory glance at real networks can make it appear that nestedness is correlated with survival, you need to delve deeper to realise this is a secondary correlation. The stronger and more causal relationship is between the number of mutualistic partners a species has and its survival."

Co-author Dr Michael Plank, also of the Department of Mathematics and Statistics at Canterbury, added: "Real-life networks, whether they are from ecology, economics, or Facebook, can be large and complex. This makes it difficult to tease apart causal relationships from confounding factors. This is where mathematical models come into their own. They allow us to systematically change one network attribute, such as nestedness, whilst controlling for other variables."

Explore further: Researcher figures out how sharks manage to act like math geniuses

More information: The paper ‘Disentangling nestedness from models of ecological complexity’ is published in that latest issue of Nature. DOI10.1038/nature11214

Related Stories

A new model for understanding biodiversity

Nov 21, 2011

(PhysOrg.com) -- Animals like foxes and raccoons are highly adaptable. They move around and eat everything from insects to eggs. They and other "generalist feeders" like them may also be crucial to sustaining ...

Biodiversity can promote survival on a warming planet

Nov 04, 2011

Whether a species can evolve to survive climate change may depend on the biodiversity of its ecological community, according to a new mathematical model that simulates the effect of climate change on plants ...

Recommended for you

New hadrosaur noses into spotlight

3 hours ago

Call it the Jimmy Durante of dinosaurs – a newly discovered hadrosaur with a truly distinctive nasal profile. The new dinosaur, named Rhinorex condrupus by paleontologists from North Carolina State Univer ...

Scholar tracks the changing world of gay sexuality

6 hours ago

With same-sex marriage now legalized in 19 states and laws making it impossible to ban homosexuals from serving in the military, gay, lesbian and bisexual people are now enjoying more freedoms and rights than ever before.

User comments : 0